Subject: Re: [PATCH v3] power: reset: at91-reset: add sysfs interface to the power on reason

From: Kamel Bouhara <[email-masked]>
Date: Mon, 9 Dec 2019 14:44:58 +0100

On Mon, Dec 09, 2019 at 11:33:23AM +0000, [email-masked] wrote:
> Hi Kamel,
>
> On 09.12.2019 11:43, Kamel Bouhara wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> >
> > 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 <[email-masked]>
> > Acked-by: Nicolas Ferre <[email-masked]>
> > ---
> > Changes in v2
> > =============
> >         - Be less specific on the crystal oscillator value
> >         - Add an Acked-by
> > Changes in v3
> > =============
> >         - Really be less specific on the crystal oscillator value
> >
> >  .../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 <[email-masked]>
> > +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,
>
> Crystal oscillator value is still present here.
>

Indeed, thanks.

> > +               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>
>
> As far as I know, headers in include/linux are only visible in kernel.
> Although you may use this header, in future, in other drivers (as Alexandre
> specified in a previous email), at the moment it is only used by
> at91-reset.c. So, why not keeping them in at91-reset.c or leave it as is
> for the moment and introduce it when this will be necessary?
>

Well, It's been a while now the idea was proposed, I've just submitted
it here.

> Moreover, you are doing 2 things on a patch:
> 1/ export the reset reasons through sysfs
> 2/ introduce the reset reason defines
>
Ok, I shall split it in two patches, if it could clarify things ?

> Thank you,
> Claudiu Beznea
>
> >  #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..9c44baa52911
> > --- /dev/null
> > +++ b/include/linux/power/power_on_reason.h
> > @@ -0,0 +1,19 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/*
> > + * Author: Kamel Bouhra <[email-masked]>
> > + */
> > +
> > +#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 */
> > --
> > 2.24.0
> >
> >
> > _______________________________________________
> > linux-arm-kernel mailing list
> > [email-masked]
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> >

--
Kamel Bouhara, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com

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