power: reset: at91-reset: add sysfs interface to the power on reason

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@bootlin.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
[Miquel Raynal: Follow-up on Kamel's work, 4 years later]
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

diff --git a/Documentation/ABI/testing/sysfs-platform-power-on-reason b/Documentation/ABI/testing/sysfs-platform-power-on-reason
new file mode 100644 (file)
index 0000000..c3b29db
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-platform-power-on-reason
@@ -0,0 +1,12 @@
+What:          /sys/devices/platform/.../power_on_reason
+Date:          June 2023
+KernelVersion: 6.5
+Contact:       Kamel Bouhara <kamel.bouhara@bootlin.com>
+Description:   Shows system power on reason. The following strings/reasons can
+               be read (the list can be extended):
+               "regular power-up", "RTC wakeup", "watchdog timeout",
+               "software reset", "reset button action", "CPU clock failure",
+               "crystal oscillator failure", "brown-out reset",
+               "unknown reason".
+
+               The file is read only.

diff --git a/drivers/power/reset/at91-reset.c b/drivers/power/reset/at91-reset.c
index d6884841a6dc66fd52e4dc41629f8c127907cc49..aa9b012d3d00b8489b4a82539aad03157987b328 100644 (file)
--- 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 const char * __init at91_reset_reason(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_REGULAR;
                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_RST_BTN;
                break;
        case RESET_TYPE_CPU_FAIL:
-               reason = "CPU clock failure detection";
+               reason = POWER_ON_REASON_CPU_CLK_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_BROWN_OUT;
                break;
        default:
-               reason = "unknown reset";
+               reason = POWER_ON_REASON_UNKNOWN;
                break;
        }
 
        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",
@@ -391,6 +402,12 @@ static int __init at91_reset_probe(struct platform_device *pdev)
        if (ret)
                goto disable_clk;
 
+       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\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 (file)
index 0000000..95a1ec0
--- /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@bootlin.com>
+ */
+
+#ifndef POWER_ON_REASON_H
+#define POWER_ON_REASON_H
+
+#define POWER_ON_REASON_REGULAR "regular power-up"
+#define POWER_ON_REASON_RTC "RTC wakeup"
+#define POWER_ON_REASON_WATCHDOG "watchdog timeout"
+#define POWER_ON_REASON_SOFTWARE "software reset"
+#define POWER_ON_REASON_RST_BTN "reset button action"
+#define POWER_ON_REASON_CPU_CLK_FAIL "CPU clock failure"
+#define POWER_ON_REASON_XTAL_FAIL "crystal oscillator failure"
+#define POWER_ON_REASON_BROWN_OUT "brown-out reset"
+#define POWER_ON_REASON_UNKNOWN "unknown reason"
+
+#endif /* POWER_ON_REASON_H */