linux-kernel - [PATCH RFC 5/6] watchdog: qcom-wdt: add support to read the restart reason from IMEM

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Message-Id: <20250408-wdt_reset_reason-v1-5-e6ec30c2c926@oss.qualcomm.com>
Date: Tue, 08 Apr 2025 14:19:55 +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>
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 RFC 5/6] watchdog: qcom-wdt: add support to read the
 restart reason 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, bootloaders update the information in the IMEM region.
Update the driver to read the restart reason from IMEM and populate the
bootstatus accordingly.

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

Signed-off-by: Kathiravan Thirumoorthy <kathiravan.thirumoorthy@....qualcomm.com>
---
 drivers/watchdog/qcom-wdt.c | 40 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 39 insertions(+), 1 deletion(-)

diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
index 006f9c61aa64fd2b4ee9db493aeb54c8fafac818..54d6eaa132ab9f63e1312a69ad51b7a14f78fe2d 100644
--- a/drivers/watchdog/qcom-wdt.c
+++ b/drivers/watchdog/qcom-wdt.c
@@ -9,6 +9,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
+#include <linux/of_address.h>
 #include <linux/platform_device.h>
 #include <linux/watchdog.h>
 
@@ -22,6 +23,8 @@ enum wdt_reg {
 
 #define QCOM_WDT_ENABLE		BIT(0)
 
+#define NON_SECURE_WDT_RESET	0x5
+
 static const u32 reg_offset_data_apcs_tmr[] = {
 	[WDT_RST] = 0x38,
 	[WDT_EN] = 0x40,
@@ -187,6 +190,39 @@ static const struct qcom_wdt_match_data match_data_kpss = {
 	.max_tick_count = 0xFFFFFU,
 };
 
+static int  qcom_wdt_get_restart_reason(struct qcom_wdt *wdt)
+{
+	struct device_node *np;
+	struct resource imem;
+	void __iomem *base;
+	int ret;
+
+	np = of_find_compatible_node(NULL, NULL, "qcom,restart-reason-info");
+	if (!np)
+		return -ENOENT;
+
+	ret = of_address_to_resource(np, 0, &imem);
+	of_node_put(np);
+	if (ret < 0) {
+		dev_err(wdt->wdd.parent, "can't translate OF node address\n");
+		return ret;
+	}
+
+	base = ioremap(imem.start, resource_size(&imem));
+	if (!base) {
+		dev_err(wdt->wdd.parent, "failed to map restart reason info region\n");
+		return -ENOMEM;
+	}
+
+	memcpy_fromio(&ret, base, sizeof(ret));
+	iounmap(base);
+
+	if (ret == NON_SECURE_WDT_RESET)
+		wdt->wdd.bootstatus = WDIOF_CARDRESET;
+
+	return 0;
+}
+
 static int qcom_wdt_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -267,7 +303,9 @@ 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)
+	ret = qcom_wdt_get_restart_reason(wdt);
+	if (ret == -ENOENT &&
+	    readl(wdt_addr(wdt, WDT_STS)) & 1)
 		wdt->wdd.bootstatus = WDIOF_CARDRESET;
 
 	/*

-- 
2.34.1