470 lines
16 KiB
Plaintext
470 lines
16 KiB
Plaintext
SAS Layer
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---------
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The SAS Layer is a management infrastructure which manages
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SAS LLDDs. It sits between SCSI Core and SAS LLDDs. The
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layout is as follows: while SCSI Core is concerned with
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SAM/SPC issues, and a SAS LLDD+sequencer is concerned with
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phy/OOB/link management, the SAS layer is concerned with:
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* SAS Phy/Port/HA event management (LLDD generates,
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SAS Layer processes),
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* SAS Port management (creation/destruction),
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* SAS Domain discovery and revalidation,
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* SAS Domain device management,
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* SCSI Host registration/unregistration,
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* Device registration with SCSI Core (SAS) or libata
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(SATA), and
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* Expander management and exporting expander control
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to user space.
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A SAS LLDD is a PCI device driver. It is concerned with
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phy/OOB management, and vendor specific tasks and generates
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events to the SAS layer.
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The SAS Layer does most SAS tasks as outlined in the SAS 1.1
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spec.
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The sas_ha_struct describes the SAS LLDD to the SAS layer.
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Most of it is used by the SAS Layer but a few fields need to
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be initialized by the LLDDs.
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After initializing your hardware, from the probe() function
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you call sas_register_ha(). It will register your LLDD with
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the SCSI subsystem, creating a SCSI host and it will
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register your SAS driver with the sysfs SAS tree it creates.
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It will then return. Then you enable your phys to actually
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start OOB (at which point your driver will start calling the
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notify_* event callbacks).
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Structure descriptions:
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struct sas_phy --------------------
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Normally this is statically embedded to your driver's
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phy structure:
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struct my_phy {
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blah;
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struct sas_phy sas_phy;
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bleh;
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};
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And then all the phys are an array of my_phy in your HA
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struct (shown below).
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Then as you go along and initialize your phys you also
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initialize the sas_phy struct, along with your own
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phy structure.
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In general, the phys are managed by the LLDD and the ports
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are managed by the SAS layer. So the phys are initialized
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and updated by the LLDD and the ports are initialized and
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updated by the SAS layer.
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There is a scheme where the LLDD can RW certain fields,
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and the SAS layer can only read such ones, and vice versa.
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The idea is to avoid unnecessary locking.
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enabled -- must be set (0/1)
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id -- must be set [0,MAX_PHYS)
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class, proto, type, role, oob_mode, linkrate -- must be set
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oob_mode -- you set this when OOB has finished and then notify
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the SAS Layer.
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sas_addr -- this normally points to an array holding the sas
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address of the phy, possibly somewhere in your my_phy
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struct.
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attached_sas_addr -- set this when you (LLDD) receive an
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IDENTIFY frame or a FIS frame, _before_ notifying the SAS
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layer. The idea is that sometimes the LLDD may want to fake
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or provide a different SAS address on that phy/port and this
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allows it to do this. At best you should copy the sas
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address from the IDENTIFY frame or maybe generate a SAS
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address for SATA directly attached devices. The Discover
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process may later change this.
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frame_rcvd -- this is where you copy the IDENTIFY/FIS frame
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when you get it; you lock, copy, set frame_rcvd_size and
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unlock the lock, and then call the event. It is a pointer
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since there's no way to know your hw frame size _exactly_,
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so you define the actual array in your phy struct and let
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this pointer point to it. You copy the frame from your
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DMAable memory to that area holding the lock.
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sas_prim -- this is where primitives go when they're
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received. See sas.h. Grab the lock, set the primitive,
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release the lock, notify.
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port -- this points to the sas_port if the phy belongs
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to a port -- the LLDD only reads this. It points to the
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sas_port this phy is part of. Set by the SAS Layer.
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ha -- may be set; the SAS layer sets it anyway.
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lldd_phy -- you should set this to point to your phy so you
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can find your way around faster when the SAS layer calls one
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of your callbacks and passes you a phy. If the sas_phy is
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embedded you can also use container_of -- whatever you
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prefer.
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struct sas_port --------------------
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The LLDD doesn't set any fields of this struct -- it only
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reads them. They should be self explanatory.
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phy_mask is 32 bit, this should be enough for now, as I
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haven't heard of a HA having more than 8 phys.
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lldd_port -- I haven't found use for that -- maybe other
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LLDD who wish to have internal port representation can make
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use of this.
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struct sas_ha_struct --------------------
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It normally is statically declared in your own LLDD
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structure describing your adapter:
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struct my_sas_ha {
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blah;
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struct sas_ha_struct sas_ha;
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struct my_phy phys[MAX_PHYS];
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struct sas_port sas_ports[MAX_PHYS]; /* (1) */
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bleh;
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};
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(1) If your LLDD doesn't have its own port representation.
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What needs to be initialized (sample function given below).
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pcidev
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sas_addr -- since the SAS layer doesn't want to mess with
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memory allocation, etc, this points to statically
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allocated array somewhere (say in your host adapter
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structure) and holds the SAS address of the host
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adapter as given by you or the manufacturer, etc.
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sas_port
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sas_phy -- an array of pointers to structures. (see
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note above on sas_addr).
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These must be set. See more notes below.
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num_phys -- the number of phys present in the sas_phy array,
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and the number of ports present in the sas_port
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array. There can be a maximum num_phys ports (one per
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port) so we drop the num_ports, and only use
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num_phys.
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The event interface:
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/* LLDD calls these to notify the class of an event. */
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void (*notify_ha_event)(struct sas_ha_struct *, enum ha_event);
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void (*notify_port_event)(struct sas_phy *, enum port_event);
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void (*notify_phy_event)(struct sas_phy *, enum phy_event);
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When sas_register_ha() returns, those are set and can be
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called by the LLDD to notify the SAS layer of such events
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the SAS layer.
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The port notification:
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/* The class calls these to notify the LLDD of an event. */
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void (*lldd_port_formed)(struct sas_phy *);
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void (*lldd_port_deformed)(struct sas_phy *);
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If the LLDD wants notification when a port has been formed
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or deformed it sets those to a function satisfying the type.
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A SAS LLDD should also implement at least one of the Task
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Management Functions (TMFs) described in SAM:
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/* Task Management Functions. Must be called from process context. */
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int (*lldd_abort_task)(struct sas_task *);
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int (*lldd_abort_task_set)(struct domain_device *, u8 *lun);
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int (*lldd_clear_aca)(struct domain_device *, u8 *lun);
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int (*lldd_clear_task_set)(struct domain_device *, u8 *lun);
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int (*lldd_I_T_nexus_reset)(struct domain_device *);
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int (*lldd_lu_reset)(struct domain_device *, u8 *lun);
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int (*lldd_query_task)(struct sas_task *);
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For more information please read SAM from T10.org.
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Port and Adapter management:
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/* Port and Adapter management */
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int (*lldd_clear_nexus_port)(struct sas_port *);
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int (*lldd_clear_nexus_ha)(struct sas_ha_struct *);
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A SAS LLDD should implement at least one of those.
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Phy management:
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/* Phy management */
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int (*lldd_control_phy)(struct sas_phy *, enum phy_func);
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lldd_ha -- set this to point to your HA struct. You can also
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use container_of if you embedded it as shown above.
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A sample initialization and registration function
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can look like this (called last thing from probe())
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*but* before you enable the phys to do OOB:
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static int register_sas_ha(struct my_sas_ha *my_ha)
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{
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int i;
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static struct sas_phy *sas_phys[MAX_PHYS];
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static struct sas_port *sas_ports[MAX_PHYS];
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my_ha->sas_ha.sas_addr = &my_ha->sas_addr[0];
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for (i = 0; i < MAX_PHYS; i++) {
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sas_phys[i] = &my_ha->phys[i].sas_phy;
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sas_ports[i] = &my_ha->sas_ports[i];
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}
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my_ha->sas_ha.sas_phy = sas_phys;
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my_ha->sas_ha.sas_port = sas_ports;
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my_ha->sas_ha.num_phys = MAX_PHYS;
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my_ha->sas_ha.lldd_port_formed = my_port_formed;
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my_ha->sas_ha.lldd_dev_found = my_dev_found;
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my_ha->sas_ha.lldd_dev_gone = my_dev_gone;
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my_ha->sas_ha.lldd_max_execute_num = lldd_max_execute_num; (1)
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my_ha->sas_ha.lldd_queue_size = ha_can_queue;
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my_ha->sas_ha.lldd_execute_task = my_execute_task;
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my_ha->sas_ha.lldd_abort_task = my_abort_task;
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my_ha->sas_ha.lldd_abort_task_set = my_abort_task_set;
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my_ha->sas_ha.lldd_clear_aca = my_clear_aca;
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my_ha->sas_ha.lldd_clear_task_set = my_clear_task_set;
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my_ha->sas_ha.lldd_I_T_nexus_reset= NULL; (2)
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my_ha->sas_ha.lldd_lu_reset = my_lu_reset;
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my_ha->sas_ha.lldd_query_task = my_query_task;
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my_ha->sas_ha.lldd_clear_nexus_port = my_clear_nexus_port;
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my_ha->sas_ha.lldd_clear_nexus_ha = my_clear_nexus_ha;
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my_ha->sas_ha.lldd_control_phy = my_control_phy;
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return sas_register_ha(&my_ha->sas_ha);
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}
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(1) This is normally a LLDD parameter, something of the
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lines of a task collector. What it tells the SAS Layer is
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whether the SAS layer should run in Direct Mode (default:
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value 0 or 1) or Task Collector Mode (value greater than 1).
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In Direct Mode, the SAS Layer calls Execute Task as soon as
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it has a command to send to the SDS, _and_ this is a single
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command, i.e. not linked.
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Some hardware (e.g. aic94xx) has the capability to DMA more
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than one task at a time (interrupt) from host memory. Task
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Collector Mode is an optional feature for HAs which support
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this in their hardware. (Again, it is completely optional
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even if your hardware supports it.)
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In Task Collector Mode, the SAS Layer would do _natural_
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coalescing of tasks and at the appropriate moment it would
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call your driver to DMA more than one task in a single HA
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interrupt. DMBS may want to use this by insmod/modprobe
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setting the lldd_max_execute_num to something greater than
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1.
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(2) SAS 1.1 does not define I_T Nexus Reset TMF.
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Events
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------
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Events are _the only way_ a SAS LLDD notifies the SAS layer
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of anything. There is no other method or way a LLDD to tell
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the SAS layer of anything happening internally or in the SAS
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domain.
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Phy events:
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PHYE_LOSS_OF_SIGNAL, (C)
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PHYE_OOB_DONE,
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PHYE_OOB_ERROR, (C)
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PHYE_SPINUP_HOLD.
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Port events, passed on a _phy_:
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PORTE_BYTES_DMAED, (M)
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PORTE_BROADCAST_RCVD, (E)
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PORTE_LINK_RESET_ERR, (C)
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PORTE_TIMER_EVENT, (C)
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PORTE_HARD_RESET.
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Host Adapter event:
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HAE_RESET
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A SAS LLDD should be able to generate
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- at least one event from group C (choice),
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- events marked M (mandatory) are mandatory (only one),
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- events marked E (expander) if it wants the SAS layer
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to handle domain revalidation (only one such).
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- Unmarked events are optional.
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Meaning:
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HAE_RESET -- when your HA got internal error and was reset.
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PORTE_BYTES_DMAED -- on receiving an IDENTIFY/FIS frame
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PORTE_BROADCAST_RCVD -- on receiving a primitive
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PORTE_LINK_RESET_ERR -- timer expired, loss of signal, loss
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of DWS, etc. (*)
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PORTE_TIMER_EVENT -- DWS reset timeout timer expired (*)
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PORTE_HARD_RESET -- Hard Reset primitive received.
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PHYE_LOSS_OF_SIGNAL -- the device is gone (*)
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PHYE_OOB_DONE -- OOB went fine and oob_mode is valid
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PHYE_OOB_ERROR -- Error while doing OOB, the device probably
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got disconnected. (*)
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PHYE_SPINUP_HOLD -- SATA is present, COMWAKE not sent.
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(*) should set/clear the appropriate fields in the phy,
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or alternatively call the inlined sas_phy_disconnected()
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which is just a helper, from their tasklet.
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The Execute Command SCSI RPC:
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int (*lldd_execute_task)(struct sas_task *, int num,
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unsigned long gfp_flags);
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Used to queue a task to the SAS LLDD. @task is the tasks to
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be executed. @num should be the number of tasks being
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queued at this function call (they are linked listed via
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task::list), @gfp_mask should be the gfp_mask defining the
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context of the caller.
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This function should implement the Execute Command SCSI RPC,
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or if you're sending a SCSI Task as linked commands, you
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should also use this function.
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That is, when lldd_execute_task() is called, the command(s)
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go out on the transport *immediately*. There is *no*
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queuing of any sort and at any level in a SAS LLDD.
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The use of task::list is two-fold, one for linked commands,
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the other discussed below.
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It is possible to queue up more than one task at a time, by
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initializing the list element of struct sas_task, and
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passing the number of tasks enlisted in this manner in num.
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Returns: -SAS_QUEUE_FULL, -ENOMEM, nothing was queued;
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0, the task(s) were queued.
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If you want to pass num > 1, then either
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A) you're the only caller of this function and keep track
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of what you've queued to the LLDD, or
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B) you know what you're doing and have a strategy of
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retrying.
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As opposed to queuing one task at a time (function call),
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batch queuing of tasks, by having num > 1, greatly
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simplifies LLDD code, sequencer code, and _hardware design_,
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and has some performance advantages in certain situations
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(DBMS).
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The LLDD advertises if it can take more than one command at
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a time at lldd_execute_task(), by setting the
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lldd_max_execute_num parameter (controlled by "collector"
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module parameter in aic94xx SAS LLDD).
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You should leave this to the default 1, unless you know what
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you're doing.
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This is a function of the LLDD, to which the SAS layer can
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cater to.
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int lldd_queue_size
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The host adapter's queue size. This is the maximum
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number of commands the lldd can have pending to domain
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devices on behalf of all upper layers submitting through
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lldd_execute_task().
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You really want to set this to something (much) larger than
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1.
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This _really_ has absolutely nothing to do with queuing.
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There is no queuing in SAS LLDDs.
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struct sas_task {
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dev -- the device this task is destined to
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list -- must be initialized (INIT_LIST_HEAD)
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task_proto -- _one_ of enum sas_proto
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scatter -- pointer to scatter gather list array
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num_scatter -- number of elements in scatter
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total_xfer_len -- total number of bytes expected to be transferred
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data_dir -- PCI_DMA_...
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task_done -- callback when the task has finished execution
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};
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DISCOVERY
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---------
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The sysfs tree has the following purposes:
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a) It shows you the physical layout of the SAS domain at
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the current time, i.e. how the domain looks in the
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physical world right now.
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b) Shows some device parameters _at_discovery_time_.
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This is a link to the tree(1) program, very useful in
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viewing the SAS domain:
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ftp://mama.indstate.edu/linux/tree/
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I expect user space applications to actually create a
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graphical interface of this.
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That is, the sysfs domain tree doesn't show or keep state if
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you e.g., change the meaning of the READY LED MEANING
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setting, but it does show you the current connection status
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of the domain device.
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Keeping internal device state changes is responsibility of
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upper layers (Command set drivers) and user space.
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When a device or devices are unplugged from the domain, this
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is reflected in the sysfs tree immediately, and the device(s)
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removed from the system.
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The structure domain_device describes any device in the SAS
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domain. It is completely managed by the SAS layer. A task
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points to a domain device, this is how the SAS LLDD knows
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where to send the task(s) to. A SAS LLDD only reads the
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contents of the domain_device structure, but it never creates
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or destroys one.
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Expander management from User Space
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-----------------------------------
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In each expander directory in sysfs, there is a file called
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"smp_portal". It is a binary sysfs attribute file, which
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implements an SMP portal (Note: this is *NOT* an SMP port),
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to which user space applications can send SMP requests and
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receive SMP responses.
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Functionality is deceptively simple:
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1. Build the SMP frame you want to send. The format and layout
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is described in the SAS spec. Leave the CRC field equal 0.
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open(2)
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2. Open the expander's SMP portal sysfs file in RW mode.
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write(2)
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3. Write the frame you built in 1.
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read(2)
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4. Read the amount of data you expect to receive for the frame you built.
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If you receive different amount of data you expected to receive,
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then there was some kind of error.
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close(2)
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All this process is shown in detail in the function do_smp_func()
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and its callers, in the file "expander_conf.c".
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The kernel functionality is implemented in the file
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"sas_expander.c".
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The program "expander_conf.c" implements this. It takes one
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argument, the sysfs file name of the SMP portal to the
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expander, and gives expander information, including routing
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tables.
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The SMP portal gives you complete control of the expander,
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so please be careful.
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