remoteproc: imx_dsp_rproc: Add remoteproc driver for DSP on i.MX

Provide a basic driver to control DSP processor found on NXP i.MX8QM,
i.MX8QXP, i.MX8MP and i.MX8ULP.

Currently it is able to resolve addresses between DSP and main CPU,
start and stop the processor, suspend and resume.

The communication between DSP and main CPU is based on mailbox, there
are three mailbox channels (tx, rx, rxdb).

This driver was tested on NXP i.MX8QM, i.MX8QXP, i.MX8MP and i.MX8ULP.

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Link: https://lore.kernel.org/r/1633944015-789-4-git-send-email-shengjiu.wang@nxp.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

drivers/remoteproc/Kconfig

@@ -34,6 +34,17 @@ config IMX_REMOTEPROC
 
 	  It's safe to say N here.
 
+config IMX_DSP_REMOTEPROC
+	tristate "i.MX DSP remoteproc support"
+	depends on ARCH_MXC
+	depends on HAVE_ARM_SMCCC
+	select MAILBOX
+	help
+	  Say y here to support iMX's DSP remote processors via the remote
+	  processor framework.
+
+	  It's safe to say N here.
+
 config INGENIC_VPU_RPROC
 	tristate "Ingenic JZ47xx VPU remoteproc support"
 	depends on MIPS || COMPILE_TEST

drivers/remoteproc/Makefile

@@ -12,6 +12,7 @@ remoteproc-y				+= remoteproc_virtio.o
 remoteproc-y				+= remoteproc_elf_loader.o
 obj-$(CONFIG_REMOTEPROC_CDEV)		+= remoteproc_cdev.o
 obj-$(CONFIG_IMX_REMOTEPROC)		+= imx_rproc.o
+obj-$(CONFIG_IMX_DSP_REMOTEPROC)	+= imx_dsp_rproc.o
 obj-$(CONFIG_INGENIC_VPU_RPROC)		+= ingenic_rproc.o
 obj-$(CONFIG_MTK_SCP)			+= mtk_scp.o mtk_scp_ipi.o
 obj-$(CONFIG_OMAP_REMOTEPROC)		+= omap_remoteproc.o