ASoC: SOF: sof-client: expose Zephyr GDB stub

Adds a DebugFS file to communicate with Zephyr's GDB stub. Communication
is via ringbuffers in shared SRAM. Both IPC3 and IPC4 are supported.

Signed-off-by: Noah Klayman <noah.klayman@intel.com>
Co-developed-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>

Author: nklayman

sound/soc/sof/Kconfig

@@ -258,6 +258,18 @@ config SND_SOC_SOF_DEBUG_IPC_KERNEL_INJECTOR
 	  Say Y if you want to enable the IPC kernel injector.
 	  If unsure, select "N".
 
+config SND_SOC_SOF_DEBUG_FW_GDB
+	tristate "SOF enable Firmware GDB debugging"
+	select SND_SOC_SOF_CLIENT
+	help
+	  This enables GDB debugging of the SOF firmware. If selected, this
+	  will make the kernel create a debugfs file, that can be used to
+	  communicate with the firmware GDB stub. When the file is opened, the
+	  kernel sends a command to the firmware to switch to the GDB mode and
+	  to wait for GDB commands. socat can be used to connect that file to a
+	  socket, to which GDB can then connect.
+	  If unsure, select "N".
+
 config SND_SOC_SOF_DEBUG_RETAIN_DSP_CONTEXT
 	bool "SOF retain DSP context on any FW exceptions"
 	help

sound/soc/sof/Makefile

@@ -35,6 +35,7 @@ endif
 ifneq ($(CONFIG_SND_SOC_SOF_IPC4),)
 snd-sof-probes-y += sof-client-probes-ipc4.o
 endif
+snd-sof-fw-gdb-objs := sof-client-fw-gdb.o
 
 snd-sof-nocodec-y := nocodec.o
 
@@ -53,6 +54,7 @@ obj-$(CONFIG_SND_SOC_SOF_DEBUG_IPC_FLOOD_TEST) += snd-sof-ipc-flood-test.o
 obj-$(CONFIG_SND_SOC_SOF_DEBUG_IPC_MSG_INJECTOR) += snd-sof-ipc-msg-injector.o
 obj-$(CONFIG_SND_SOC_SOF_DEBUG_IPC_KERNEL_INJECTOR) += snd-sof-ipc-kernel-injector.o
 obj-$(CONFIG_SND_SOC_SOF_DEBUG_PROBES) += snd-sof-probes.o
+obj-$(CONFIG_SND_SOC_SOF_DEBUG_FW_GDB) += snd-sof-fw-gdb.o
 
 obj-$(CONFIG_SND_SOC_SOF_INTEL_TOPLEVEL) += intel/
 obj-$(CONFIG_SND_SOC_SOF_IMX_TOPLEVEL) += imx/