[PATCH 2/2] power: reset: at91-reset: add sysfs interface to the power on reason

[Miquel Raynal]

From: Kamel Bouhara <kamel.bouhara at bootlin.com>

Introduce a list of generic reset sources and use them to export the
power on reason through sysfs. Update the ABI documentation to describe
this new interface.

Signed-off-by: Kamel Bouhara <kamel.bouhara at bootlin.com>
Acked-by: Nicolas Ferre <nicolas.ferre at microchip.com>
[Miquel Raynal: Follow-up on Kamel's work, 4 years later]
Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>
---
 .../testing/sysfs-platform-power-on-reason    | 10 +++++
 drivers/power/reset/at91-reset.c              | 42 +++++++++++++------
 include/linux/power/power_on_reason.h         | 19 +++++++++
 3 files changed, 59 insertions(+), 12 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-platform-power-on-reason
 create mode 100644 include/linux/power/power_on_reason.h

diff --git a/Documentation/ABI/testing/sysfs-platform-power-on-reason b/Documentation/ABI/testing/sysfs-platform-power-on-reason
new file mode 100644
index 000000000000..12020d017543
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-platform-power-on-reason
@@ -0,0 +1,10 @@
+What:		/sys/devices/platform/.../power_on_reason
+Date:		October 2019
+KernelVersion:	5.4
+Contact:	Kamel Bouhara <kamel.bouhara at bootlin.com>
+Description:	This file shows system power on reason. Possible sources are:
+		General system power-on, RTC wakeup, watchdog timeout, software
+		reset, user pressed reset button, CPU clock failure, oscillator
+		failure, low power mode exit, unknown.
+
+		The file is read only.
diff --git a/drivers/power/reset/at91-reset.c b/drivers/power/reset/at91-reset.c
index a8a6f3997768..73cc6839a1c1 100644
--- a/drivers/power/reset/at91-reset.c
+++ b/drivers/power/reset/at91-reset.c
@@ -18,6 +18,7 @@
 #include <linux/platform_device.h>
 #include <linux/reboot.h>
 #include <linux/reset-controller.h>
+#include <linux/power/power_on_reason.h>
 
 #include <soc/at91/at91sam9_ddrsdr.h>
 #include <soc/at91/at91sam9_sdramc.h>
@@ -149,44 +150,54 @@ static int at91_reset(struct notifier_block *this, unsigned long mode,
 	return NOTIFY_DONE;
 }
 
-static void __init at91_reset_status(struct at91_reset *reset)
+static const char *at91_reset_reason(struct at91_reset *reset)
 {
 	u32 reg = readl(reset->rstc_base + AT91_RSTC_SR);
 	const char *reason;
 
 	switch ((reg & AT91_RSTC_RSTTYP) >> 8) {
 	case RESET_TYPE_GENERAL:
-		reason = "general reset";
+		reason = POWER_ON_REASON_GENERAL;
 		break;
 	case RESET_TYPE_WAKEUP:
-		reason = "wakeup";
+		reason = POWER_ON_REASON_RTC;
 		break;
 	case RESET_TYPE_WATCHDOG:
-		reason = "watchdog reset";
+		reason = POWER_ON_REASON_WATCHDOG;
 		break;
 	case RESET_TYPE_SOFTWARE:
-		reason = "software reset";
+		reason = POWER_ON_REASON_SOFTWARE;
 		break;
 	case RESET_TYPE_USER:
-		reason = "user reset";
+		reason = POWER_ON_REASON_USER;
 		break;
 	case RESET_TYPE_CPU_FAIL:
-		reason = "CPU clock failure detection";
+		reason = POWER_ON_REASON_CPU_FAIL;
 		break;
 	case RESET_TYPE_XTAL_FAIL:
-		reason = "32.768 kHz crystal failure detection";
+		reason = POWER_ON_REASON_XTAL_FAIL;
 		break;
 	case RESET_TYPE_ULP2:
-		reason = "ULP2 reset";
+		reason = POWER_ON_REASON_LOW_POWER;
 		break;
 	default:
-		reason = "unknown reset";
+		reason = POWER_ON_REASON_UNKNOWN;
 		break;
 	}
 
-	dev_info(&pdev->dev, "Starting after %s\n", reason);
+	return reason;
 }
 
+static ssize_t power_on_reason_show(struct device *dev,
+				    struct device_attribute *attr, char *buf)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct at91_reset *reset = platform_get_drvdata(pdev);
+
+	return sprintf(buf, "%s\n", at91_reset_reason(reset));
+}
+static DEVICE_ATTR_RO(power_on_reason);
+
 static const struct of_device_id at91_ramc_of_match[] = {
 	{
 		.compatible = "atmel,at91sam9260-sdramc",
@@ -391,7 +402,14 @@ static int __init at91_reset_probe(struct platform_device *pdev)
 	if (ret)
 		goto disable_clk;
 
-	at91_reset_status(pdev, reset->rstc_base);
+	ret = device_create_file(&pdev->dev, &dev_attr_power_on_reason);
+	if (ret) {
+		dev_err(&pdev->dev, "Could not create sysfs entry\n");
+		return ret;
+	}
+
+	dev_info(&pdev->dev, "Starting after %s reset\n",
+		 at91_reset_reason(reset));
 
 	return 0;
 
diff --git a/include/linux/power/power_on_reason.h b/include/linux/power/power_on_reason.h
new file mode 100644
index 000000000000..4b92eb0519c4
--- /dev/null
+++ b/include/linux/power/power_on_reason.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Author: Kamel Bouhra <kamel.bouhara at bootlin.com>
+ */
+
+#ifndef POWER_ON_REASON_H
+#define POWER_ON_REASON_H
+
+#define POWER_ON_REASON_GENERAL "general"
+#define POWER_ON_REASON_RTC "RTC wakeup"
+#define POWER_ON_REASON_WATCHDOG "watchdog timeout"
+#define POWER_ON_REASON_SOFTWARE "software"
+#define POWER_ON_REASON_USER "user"
+#define POWER_ON_REASON_CPU_FAIL "CPU clock failure"
+#define POWER_ON_REASON_XTAL_FAIL "crystal oscillator failure"
+#define POWER_ON_REASON_LOW_POWER "low power exit"
+#define POWER_ON_REASON_UNKNOWN "unknown"
+
+#endif /* POWER_ON_REASON_H */
-- 
2.34.1