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

[Eugen.Hristev]

On 29.11.2019 13:02, Alexandre Belloni wrote:

> On 29/11/2019 10:57:45+0000, Claudiu.Beznea@xxxxxxxxxxxxx wrote:
>> Hi Kamel,
>>
>> On 17.10.2019 15:40, Kamel Bouhara wrote:
>>> This patch export the power on reason through the sysfs interface and
>>> introduce some generic reset sources.
>>> Update the ABI documentation to list current power on sources.
>>>
>>> Signed-off-by: Kamel Bouhara <kamel.bouhara@xxxxxxxxxxx>
>>> ---
>>>   .../sysfs-devices-platform-power-on-reason    | 14 ++++++
>>>   drivers/power/reset/at91-reset.c              | 44 +++++++++++++------
>>>   include/linux/power/power_on_reason.h         | 19 ++++++++
>>>   3 files changed, 64 insertions(+), 13 deletions(-)
>>>   create mode 100644 Documentation/ABI/testing/sysfs-devices-platform-power-on-reason
>>>   create mode 100644 include/linux/power/power_on_reason.h
>>>
>>> diff --git a/Documentation/ABI/testing/sysfs-devices-platform-power-on-reason b/Documentation/ABI/testing/sysfs-devices-platform-power-on-reason
>>> new file mode 100644
>>> index 000000000000..83daeb9b1aa2
>>> --- /dev/null
>>> +++ b/Documentation/ABI/testing/sysfs-devices-platform-power-on-reason
>>> @@ -0,0 +1,14 @@
>>> +What:              /sys/devices/platform/.../power_on_reason
>>> +
>>> +Date:              October 2019
>>> +KernelVersion:     5.4
>>> +Contact:   Kamel Bouhara <kamel.bouhara@xxxxxxxxxxx>
>>> +Description:       This file shows system power on reason.
>>> +           The possible sources are:
>>> +           General System Power-ON, RTC wakeup, Watchdog timeout,
>>> +           Software Reset, User pressed reset button,
>>> +           CPU Clock failure, 32.768kHz 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 44ca983a49a1..3cb2df40af37 100644
>>> --- a/drivers/power/reset/at91-reset.c
>>> +++ b/drivers/power/reset/at91-reset.c
>>> @@ -17,7 +17,7 @@
>>>   #include <linux/of_address.h>
>>>   #include <linux/platform_device.h>
>>>   #include <linux/reboot.h>
>>> -
>>> +#include <linux/power/power_on_reason.h>
>>>   #include <soc/at91/at91sam9_ddrsdr.h>
>>>   #include <soc/at91/at91sam9_sdramc.h>
>>>
>>> @@ -146,42 +146,42 @@ static int samx7_restart(struct notifier_block *this, unsigned long mode,
>>>      return NOTIFY_DONE;
>>>   }
>>>
>>> -static void __init at91_reset_status(struct platform_device *pdev)
>>> +static const char *at91_reset_reason(struct platform_device *pdev)
>>>   {
>>>      const char *reason;
>>>      u32 reg = readl(at91_rstc_base + AT91_RSTC_SR);
>>>
>>>      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 const struct of_device_id at91_ramc_of_match[] = {
>>> @@ -204,6 +204,17 @@ static struct notifier_block at91_restart_nb = {
>>>      .priority = 192,
>>>   };
>>>
>>> +static ssize_t power_on_reason_show(struct device *dev,
>>> +                               struct device_attribute *attr,
>>> +                               char *buf)
>>> +{
>>> +   struct platform_device *pdev = to_platform_device(dev);
>>> +
>>> +   return sprintf(buf, "%s\n", at91_reset_reason(pdev));
>>> +}
>>> +
>>> +static DEVICE_ATTR_RO(power_on_reason);
>>> +
>>>   static int __init at91_reset_probe(struct platform_device *pdev)
>>>   {
>>>      const struct of_device_id *match;
>>> @@ -248,7 +259,14 @@ static int __init at91_reset_probe(struct platform_device *pdev)
>>>              return ret;
>>>      }
>>>
>>> -   at91_reset_status(pdev);
>>> +   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(pdev));
>>>
>>>      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..9978cc757427
>>> --- /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@xxxxxxxxxxx>
>>> + */
>>> +
>>> +#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 "32.768k Crystal oscillator Failure"

Hi,

Looks rather odd to have a hardcoded crystal value inside a generic header.
Also how is REASON_CPU_FAIL related to CPU Clock ?

Eugen

>>> +#define POWER_ON_REASON_LOW_POWER "Low power exit"
>>> +#define POWER_ON_REASON_UNKNOWN "Unknown"
>>> +
>>> +#endif /* POWER_ON_REASON_H */
>>
>> Is this new header necessary?
>>
> 
> Yes because we want other drivers to be able to reuse them as-is so the
> ABI is stable.
> 
> --
> Alexandre Belloni, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com
> 
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