watchdog: rti_wdt: Add support for loading firmware

To avoid the need of extra boot scripting on AM65x for loading a
watchdog firmware, add the required rproc init and loading logic for the
first R5F core to the watchdog start handler. In case the R5F cluster is
in lock-step mode, also initialize the second core. The firmware itself
is embedded into U-Boot binary to ease access to it and ensure it is
properly hashed in case of secure boot.

One possible firmware source is https://github.com/siemens/k3-rti-wdt.

The board is responsible for providing the firmware as additional
loadable via the U-Boot fit image. The driver will pick up its location
from /fit-images/k3-rti-wdt-firmware then.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

2 files changed, 108 insertions, 0 deletions

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index eaa6f16..7d2d6ea 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -218,6 +218,26 @@ config WDT_K3_RTI
 	  Say Y here if you want to include support for the K3 watchdog
 	  timer (RTI module) available in the K3 generation of processors.
 
+if WDT_K3_RTI
+
+config WDT_K3_RTI_LOAD_FW
+	bool "Load watchdog firmware"
+	depends on REMOTEPROC
+	help
+	  Automatically load the specified firmware image into the MCU R5F
+	  core 0. On the AM65x, this firmware is supposed to handle the expiry
+	  of the watchdog timer, typically by resetting the system.
+
+config WDT_K3_RTI_FW_FILE
+	string "Watchdog firmware image file"
+	default "k3-rti-wdt.fw"
+	depends on WDT_K3_RTI_LOAD_FW
+	help
+	  Firmware image to be embedded into U-Boot and loaded on watchdog
+	  start.
+
+endif
+
 config WDT_SANDBOX
 	bool "Enable Watchdog Timer support for Sandbox"
 	depends on SANDBOX && WDT
diff --git a/drivers/watchdog/rti_wdt.c b/drivers/watchdog/rti_wdt.c
index 8335b20..253286d 100644
--- a/drivers/watchdog/rti_wdt.c
+++ b/drivers/watchdog/rti_wdt.c
@@ -11,9 +11,11 @@
 #include <common.h>
 #include <clk.h>
 #include <dm.h>
+#include <dm/device_compat.h>
 #include <power-domain.h>
 #include <wdt.h>
 #include <asm/io.h>
+#include <remoteproc.h>
 
 /* Timer register set definition */
 #define RTIDWDCTRL		0x90
@@ -42,6 +44,88 @@ struct rti_wdt_priv {
 	unsigned int clk_khz;
 };
 
+#ifdef CONFIG_WDT_K3_RTI_LOAD_FW
+#define RTI_WDT_FIT_PATH	"/fit-images/k3-rti-wdt-firmware"
+
+static int rti_wdt_load_fw(struct udevice *dev)
+{
+	struct udevice *rproc_dev;
+	int primary_core, ret;
+	u32 cluster_mode;
+	ofnode node;
+	u64 rti_wdt_fw;
+	u32 rti_wdt_fw_size;
+
+	node = ofnode_path(RTI_WDT_FIT_PATH);
+	if (!ofnode_valid(node))
+		goto fit_error;
+
+	ret = ofnode_read_u64(node, "load", &rti_wdt_fw);
+	if (ret)
+		goto fit_error;
+	ret = ofnode_read_u32(node, "size", &rti_wdt_fw_size);
+	if (ret)
+		goto fit_error;
+
+	node = ofnode_by_compatible(ofnode_null(), "ti,am654-r5fss");
+	if (!ofnode_valid(node))
+		goto dt_error;
+
+	ret = ofnode_read_u32(node, "ti,cluster-mode", &cluster_mode);
+	if (ret)
+		cluster_mode = 1;
+
+	node = ofnode_by_compatible(node, "ti,am654-r5f");
+	if (!ofnode_valid(node))
+		goto dt_error;
+
+	ret = uclass_get_device_by_ofnode(UCLASS_REMOTEPROC, node, &rproc_dev);
+	if (ret)
+		return ret;
+
+	primary_core = dev_seq(rproc_dev);
+
+	ret = rproc_dev_init(primary_core);
+	if (ret)
+		goto fw_error;
+
+	if (cluster_mode == 1) {
+		ret = rproc_dev_init(primary_core + 1);
+		if (ret)
+			goto fw_error;
+	}
+
+	ret = rproc_load(primary_core, (ulong)rti_wdt_fw,
+			 rti_wdt_fw_size);
+	if (ret)
+		goto fw_error;
+
+	ret = rproc_start(primary_core);
+	if (ret)
+		goto fw_error;
+
+	return 0;
+
+fit_error:
+	dev_err(dev, "No loadable firmware found under %s\n", RTI_WDT_FIT_PATH);
+	return -ENOENT;
+
+dt_error:
+	dev_err(dev, "No compatible firmware target processor found\n");
+	return -ENODEV;
+
+fw_error:
+	dev_err(dev, "Failed to load watchdog firmware into remote processor %d\n",
+		primary_core);
+	return ret;
+}
+#else
+static inline int rti_wdt_load_fw(struct udevice *dev)
+{
+	return 0;
+}
+#endif
+
 static int rti_wdt_start(struct udevice *dev, u64 timeout_ms, ulong flags)
 {
 	struct rti_wdt_priv *priv = dev_get_priv(dev);
@@ -51,6 +135,10 @@ static int rti_wdt_start(struct udevice *dev, u64 timeout_ms, ulong flags)
 	if (readl(priv->regs + RTIDWDCTRL) == WDENABLE_KEY)
 		return -EBUSY;
 
+	ret = rti_wdt_load_fw(dev);
+	if (ret < 0)
+		return ret;
+
 	timer_margin = timeout_ms * priv->clk_khz / 1000;
 	timer_margin >>= WDT_PRELOAD_SHIFT;
 	if (timer_margin > WDT_PRELOAD_MAX)