linux-kernel - [PATCH v5 4/5] watchdog: qcom: add support to get the bootstatus from IMEM

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Message-Id: <20250610-wdt_reset_reason-v5-4-2d2835160ab5@oss.qualcomm.com>
Date: Tue, 10 Jun 2025 19:15:20 +0530
From: Kathiravan Thirumoorthy <kathiravan.thirumoorthy@....qualcomm.com>
To: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Rajendra Nayak <quic_rjendra@...cinc.com>
Cc: linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-watchdog@...r.kernel.org,
        Kathiravan Thirumoorthy <kathiravan.thirumoorthy@....qualcomm.com>
Subject: [PATCH v5 4/5] watchdog: qcom: add support to get the bootstatus
 from IMEM

When the system boots up after a watchdog reset, the EXPIRED_STATUS bit
in the WDT_STS register is cleared. To identify if the system was
restarted due to WDT expiry, XBL update the information in the IMEM region.
Update the driver to read the restart reason from IMEM and populate the
bootstatus accordingly.

With the CONFIG_WATCHDOG_SYSFS enabled, user can extract the information
as below:

cat /sys/devices/platform/soc@...410000.watchdog/watchdog/watchdog0/bootstatus
32

For backward compatibility, keep the EXPIRED_STATUS bit check. Add a new
function qcom_wdt_get_bootstatus() to read the restart reason from
IMEM.

Signed-off-by: Kathiravan Thirumoorthy <kathiravan.thirumoorthy@....qualcomm.com>
---
Changes in v5:
	- Use dev_err_probe instead of dev_err

Changes in v4:
	- Kept only WDIOF_CARDRESET and dropped other codes
	- Renamed qcom_wdt_get_reason_reason() to
	  qcom_wdt_get_bootstatus()
	- Moved the existing check inside qcom_wdt_get_bootstatus()
	- Dropped the device data and put all the details in the DT node

Changes in v3:
	- Split the introduction of device data into separate patch
	- s/bootloaders/XBL - for clarity of which bootloader is
	  involved
	- Mention the sysfs path on to extract this information
	- s/compatible/imem_compatible in the device data structure to
	  avoid the confusion / better naming

Changes in v2:
	- Use the syscon API to access the IMEM region
	- Handle the error cases returned by qcom_wdt_get_restart_reason
	- Define device specific data to retrieve the IMEM compatible,
	  offset and the value for non secure WDT, which allows to
	  extend the support for other SoCs
---
 drivers/watchdog/qcom-wdt.c | 43 +++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 41 insertions(+), 2 deletions(-)

diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
index dfaac5995c84c1f377023e6e62770c5548528a4c..795f409506c6bb1dfb26cd8af18bece3cc35aebf 100644
--- a/drivers/watchdog/qcom-wdt.c
+++ b/drivers/watchdog/qcom-wdt.c
@@ -7,9 +7,11 @@
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
+#include <linux/regmap.h>
 #include <linux/watchdog.h>
 
 enum wdt_reg {
@@ -193,6 +195,42 @@ static const struct qcom_wdt_match_data match_data_kpss = {
 	.max_tick_count = 0xFFFFFU,
 };
 
+static int qcom_wdt_get_bootstatus(struct device *dev, struct qcom_wdt *wdt)
+{
+	unsigned int args[2];
+	struct regmap *imem;
+	unsigned int val;
+	int ret;
+
+	imem = syscon_regmap_lookup_by_phandle_args(dev->of_node, "sram",
+						    ARRAY_SIZE(args), args);
+	if (IS_ERR(imem)) {
+		ret = PTR_ERR(imem);
+		if (ret != -ENOENT) {
+			dev_err_probe(dev, ret, "Failed to lookup syscon\n");
+			return ret;
+		}
+
+		/* Fallback to the existing check */
+		if (readl(wdt_addr(wdt, WDT_STS)) & 1)
+			wdt->wdd.bootstatus = WDIOF_CARDRESET;
+
+		return 0;
+	}
+
+	ret = regmap_read(imem, args[0], &val);
+	if (ret) {
+		dev_err_probe(dev, ret,
+			      "Failed to read the restart reason info\n");
+		return ret;
+	}
+
+	if (val == args[1])
+		wdt->wdd.bootstatus = WDIOF_CARDRESET;
+
+	return 0;
+}
+
 static int qcom_wdt_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -273,8 +311,9 @@ static int qcom_wdt_probe(struct platform_device *pdev)
 	wdt->wdd.parent = dev;
 	wdt->layout = data->offset;
 
-	if (readl(wdt_addr(wdt, WDT_STS)) & 1)
-		wdt->wdd.bootstatus = WDIOF_CARDRESET;
+	ret = qcom_wdt_get_bootstatus(dev, wdt);
+	if (ret)
+		return ret;
 
 	/*
 	 * If 'timeout-sec' unspecified in devicetree, assume a 30 second

-- 
2.34.1