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incubator-nuttx/drivers/misc/lwl_console.c

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/****************************************************************************
* drivers/misc/lwl_console.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <errno.h>
#include <debug.h>
#include <nuttx/fs/fs.h>
#include <nuttx/drivers/drivers.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* Lightweight Link (lwl)
* ======================
*
* Lightweight bidirectional communication between target and debug host
* without any need for additional hardware.
*
* Works with openOCD and other debuggers that are capable of reading and
* writing memory while the target is running.
*
* Principle of operation is simple; An 'upword' of 32 bits communicates
* from the target to the host, a 'downword' of the same size runs in the
* opposite direction. These two words can be in any memory that is
* read/write access for both the target and the debug host. A simple ping
* pong handshake protocol over these words allows up/down link
* communication. On the upside no additional integration is needed. On
* the downside it may be necessary to feed lwl with cycles to poll for
* changes in the downword, depending on the use case.
*
* Bit configuration
* -----------------
*
* Downword (Host to target);
*
* A D U VV XXX
*
* A 31 1 - Service Active (Set by host)
* D 30 1 - Downsense (Toggled when there is data)
* U 29 1 - Upsense ack (Toggled to acknowledge receipt of uplink data)
* VV 28-27 2 - Valid Octets (Number of octets valid in the message)
* XXX 26-24 3 - Port in use (Type of the message)
* O2 23-16 8 - Octet 2
* O1 15-08 8 - Octet 1
* O0 07-00 8 - Octet 0
*
* Upword (Target to Host);
*
* A 31 1 - Service Active (Set by device)
* D 30 1 - Downsense ack (Toggled to acknowledge receipt of downlink
* data)
* U 29 1 - Upsense (Toggled when there is data)
* VV 28-27 2 - Valid upword octets
* XXX 26-24 3 - Port in use (Type of the message)
* O2 23-16 8 - Octet 2
* O1 15-08 8 - Octet 1
* O0 07-00 8 - Octet 0
*
*/
/* Protocol bits */
#define LWL_GETACTIVE(x) (((x) & (1 << 31)) != 0)
#define LWL_ACTIVE(x) (((x)&1) << 31)
#define LWL_DNSENSEBIT (1 << 30)
#define LWL_DNSENSE(x) ((x)&LWL_DNSENSEBIT)
#define LWL_UPSENSEBIT (1 << 29)
#define LWL_UPSENSE(x) ((x)&LWL_UPSENSEBIT)
#define LWL_SENSEMASK (3 << 29)
#define LWL_GETOCTVAL(x) (((x) >> 27) & 3)
#define LWL_OCTVAL(x) (((x)&3) << 27)
#define LWL_GETPORT(x) (((x) >> 24) & 7)
#define LWL_PORT(x) (((x)&7) << 24)
#define LWL_PORT_CONSOLE 1
#define LWL_ID_SIG 0x7216A318
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static ssize_t lwlconsole_read(FAR struct file *filep, FAR char *buffer,
size_t buflen);
static ssize_t lwlconsole_write(FAR struct file *filep,
FAR const char *buffer, size_t buflen);
/****************************************************************************
* Private Data
****************************************************************************/
struct lwl_entry_s
{
uint32_t sig; /* Location signature */
volatile uint32_t downword; /* Host to Target word */
uint32_t upword; /* Target to Host word */
};
static struct lwl_entry_s g_d =
{
LWL_ID_SIG
};
static const struct file_operations g_consoleops =
{
NULL, /* open */
NULL, /* close */
lwlconsole_read, /* read */
lwlconsole_write, /* write */
};
/****************************************************************************
* Private Functions
****************************************************************************/
static bool linkactive(void)
{
return (LWL_GETACTIVE(g_d.downword) != 0);
}
static bool writeword(uint32_t newupword)
{
/* Check link is active */
if (!linkactive())
{
return false;
}
/* Spin waiting for previous data to be collected */
while (LWL_UPSENSE(g_d.downword) != LWL_UPSENSE(g_d.upword))
{
}
/* Load new data, toggling UPSENSE bit to show it is new */
g_d.upword = LWL_DNSENSE(g_d.upword) | newupword |
(LWL_UPSENSE(g_d.upword) ? 0 : LWL_UPSENSEBIT);
return true;
}
static bool write8bits(uint8_t port, uint8_t val)
{
/* Prepare new word */
uint32_t newupword = LWL_ACTIVE(true) | LWL_OCTVAL(1) |
LWL_PORT(port) | (val & 0xff);
return writeword(newupword);
}
static bool write16bits(uint8_t port, uint32_t val)
{
/* Prepare new word */
uint32_t newupword = LWL_ACTIVE(true) | LWL_OCTVAL(2) |
LWL_PORT(port) | (val & 0xffff);
return writeword(newupword);
}
static bool write24bits(uint8_t port, uint32_t val)
{
/* Prepare new word */
uint32_t newupword = LWL_ACTIVE(true) | LWL_OCTVAL(3) |
LWL_PORT(port) | (val & 0xffffff);
return writeword(newupword);
}
static bool read8bits(uint8_t port, FAR uint8_t *store)
{
if (!linkactive())
{
return false;
}
/* Spin waiting for a byte to be received */
while (LWL_DNSENSE(g_d.downword) == LWL_DNSENSE(g_d.upword))
{
}
*store = g_d.downword & 255;
/* Flip the bit to indicate the datum is read */
g_d.upword = (g_d.upword & ~LWL_DNSENSEBIT) | LWL_DNSENSE(g_d.downword);
return true;
}
/****************************************************************************
* Name: lwlconsole_read
****************************************************************************/
static ssize_t lwlconsole_read(FAR struct file *filep, FAR char *buffer,
size_t buflen)
{
if (buflen == 0)
{
return 0;
}
if (!read8bits(LWL_PORT_CONSOLE, (FAR uint8_t *) buffer))
{
return 0;
}
return 1;
}
/****************************************************************************
* Name: lwlconsole_write
****************************************************************************/
static ssize_t lwlconsole_write(FAR struct file *filep,
FAR const char *buffer, size_t buflen)
{
uint32_t oc = 0;
while (buflen)
{
switch (buflen)
{
case 0:
return oc;
case 1:
if (write8bits(LWL_PORT_CONSOLE, buffer[0]))
{
oc++;
buffer++;
buflen--;
}
break;
case 2:
if (write16bits(LWL_PORT_CONSOLE, buffer[0] | (buffer[1] << 8)))
{
oc += 2;
buffer += 2;
buflen -= 2;
}
break;
default:
if (write24bits(LWL_PORT_CONSOLE, buffer[0] |
(buffer[1] << 8) | (buffer[2] << 16)))
{
oc += 3;
buffer += 3;
buflen -= 3;
}
break;
}
}
return oc;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: lwlconsole_init
****************************************************************************/
void lwlconsole_init(void)
{
register_driver("/dev/console", &g_consoleops, 0666, NULL);
}
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