[PATCH v3 05/13] power-domain: Add refcounting

[Simon Glass]

Hi Miquel,

On Fri, 10 Jan 2025 at 11:43, Miquel Raynal <miquel.raynal at bootlin.com> wrote:
>
> It is very surprising that such an uclass, specifically designed to
> handle resources that may be shared by different devices, is not keeping
> the count of the number of times a power domain has been
> enabled/disabled to avoid shutting it down unexpectedly or disabling it
> several times.
>
> Doing this causes troubles on eg. i.MX8MP because disabling power
> domains can be done in recursive loops were the same power domain
> disabled up to 4 times in a row. PGCs seem to have tight FSM internal
> timings to respect and it is easy to produce a race condition that puts
> the power domains in an unstable state, leading to ADB400 errors and
> later crashes in Linux.
>
> CI tests using power domains are slightly updated to make sure the count
> of on/off calls is even and the results match what we *now* expect.
>
> Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>
> ---
>  drivers/firmware/scmi/sandbox-scmi_devices.c     |  1 +
>  drivers/power/domain/power-domain-uclass.c       | 37 ++++++++++++++++++++++--
>  drivers/power/domain/sandbox-power-domain-test.c |  1 +
>  include/power-domain.h                           |  4 +--
>  test/dm/power-domain.c                           |  2 +-
>  5 files changed, 40 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/firmware/scmi/sandbox-scmi_devices.c b/drivers/firmware/scmi/sandbox-scmi_devices.c
> index 96c2922b067e2886b3fa963bcd7e396f4569a569..9f253b0fd40f703a5ec11d34c197423d27ad8b01 100644
> --- a/drivers/firmware/scmi/sandbox-scmi_devices.c
> +++ b/drivers/firmware/scmi/sandbox-scmi_devices.c
> @@ -163,4 +163,5 @@ U_BOOT_DRIVER(sandbox_scmi_devices) = {
>         .priv_auto = sizeof(struct sandbox_scmi_device_priv),
>         .remove = sandbox_scmi_devices_remove,
>         .probe = sandbox_scmi_devices_probe,
> +       .flags = DM_FLAG_DEFAULT_PD_CTRL_OFF,
>  };
> diff --git a/drivers/power/domain/power-domain-uclass.c b/drivers/power/domain/power-domain-uclass.c
> index 938bd8cbc9ffd1ba2109d702f886b6a99288d063..55a3d95d83c5aaac31acbd877199c87f8f6fb880 100644
> --- a/drivers/power/domain/power-domain-uclass.c
> +++ b/drivers/power/domain/power-domain-uclass.c
> @@ -12,6 +12,10 @@
>  #include <power-domain-uclass.h>
>  #include <dm/device-internal.h>
>
> +struct power_domain_priv {
> +       int on_count;
> +};
> +
>  static inline struct power_domain_ops *power_domain_dev_ops(struct udevice *dev)
>  {
>         return (struct power_domain_ops *)dev->driver->ops;
> @@ -110,19 +114,47 @@ int power_domain_free(struct power_domain *power_domain)
>  int power_domain_on(struct power_domain *power_domain)
>  {
>         struct power_domain_ops *ops = power_domain_dev_ops(power_domain->dev);
> +       struct power_domain_priv *priv = dev_get_uclass_priv(power_domain->dev);
> +       int ret;
>
>         debug("%s(power_domain=%p)\n", __func__, power_domain);
>
> -       return ops->on ? ops->on(power_domain) : 0;
> +       if (priv->on_count++ > 0)
> +               return 0;

-EALREADY

> +
> +       ret = ops->on ? ops->on(power_domain) : 0;
> +       if (ret) {
> +               priv->on_count--;
> +               return ret;
> +       }
> +
> +       return 0;
>  }
>
>  int power_domain_off(struct power_domain *power_domain)
>  {
>         struct power_domain_ops *ops = power_domain_dev_ops(power_domain->dev);
> +       struct power_domain_priv *priv = dev_get_uclass_priv(power_domain->dev);
> +       int ret;
>
>         debug("%s(power_domain=%p)\n", __func__, power_domain);
>
> -       return ops->off ? ops->off(power_domain) : 0;
> +       if (priv->on_count <= 0) {
> +               debug("Power domain %s already off.\n", power_domain->dev->name);
> +               priv->on_count--;
> +               return 0;
> +       }
> +
> +       if (priv->on_count-- > 1)
> +               return 0;

-EBUSY

See how the regulator uclass does it.

> +
> +       ret = ops->off ? ops->off(power_domain) : 0;
> +       if (ret) {
> +               priv->on_count++;
> +               return ret;
> +       }
> +
> +       return 0;
>  }
>
>  #if CONFIG_IS_ENABLED(OF_REAL)
> @@ -180,4 +212,5 @@ int dev_power_domain_off(struct udevice *dev)
>  UCLASS_DRIVER(power_domain) = {
>         .id             = UCLASS_POWER_DOMAIN,
>         .name           = "power_domain",
> +       .per_device_auto = sizeof(struct power_domain_priv),
>  };
> diff --git a/drivers/power/domain/sandbox-power-domain-test.c b/drivers/power/domain/sandbox-power-domain-test.c
> index 08c15ef342b3dd3ce01807ee59b7e97337f7dde5..5b530974e942ffcba453e53be330baaf3a113a13 100644
> --- a/drivers/power/domain/sandbox-power-domain-test.c
> +++ b/drivers/power/domain/sandbox-power-domain-test.c
> @@ -51,4 +51,5 @@ U_BOOT_DRIVER(sandbox_power_domain_test) = {
>         .id = UCLASS_MISC,
>         .of_match = sandbox_power_domain_test_ids,
>         .priv_auto      = sizeof(struct sandbox_power_domain_test),
> +       .flags = DM_FLAG_DEFAULT_PD_CTRL_OFF,
>  };
> diff --git a/include/power-domain.h b/include/power-domain.h
> index 18525073e5e3534fcbac6fae4e18462f29a4dc49..0266fc2f864ef3645d2a8b3c6fa66fdbd868799c 100644
> --- a/include/power-domain.h
> +++ b/include/power-domain.h
> @@ -147,7 +147,7 @@ static inline int power_domain_free(struct power_domain *power_domain)
>  #endif
>
>  /**
> - * power_domain_on - Enable power to a power domain.
> + * power_domain_on - Enable power to a power domain (with refcounting)
>   *
>   * @power_domain:      A power domain struct that was previously successfully
>   *             requested by power_domain_get().
> @@ -163,7 +163,7 @@ static inline int power_domain_on(struct power_domain *power_domain)
>  #endif
>
>  /**
> - * power_domain_off - Disable power to a power domain.
> + * power_domain_off - Disable power to a power domain (with refcounting)
>   *
>   * @power_domain:      A power domain struct that was previously successfully
>   *             requested by power_domain_get().
> diff --git a/test/dm/power-domain.c b/test/dm/power-domain.c
> index 896cf5b2ae9d26701150fad70e888f8b135a22b0..8a95f6bdb903be9d1993528d87d5cae0075a83e4 100644
> --- a/test/dm/power-domain.c
> +++ b/test/dm/power-domain.c
> @@ -27,7 +27,7 @@ static int dm_test_power_domain(struct unit_test_state *uts)
>
>         ut_assertok(uclass_get_device_by_name(UCLASS_MISC, "power-domain-test",
>                                               &dev_test));
> -       ut_asserteq(1, sandbox_power_domain_query(dev_power_domain,
> +       ut_asserteq(0, sandbox_power_domain_query(dev_power_domain,
>                                                   TEST_POWER_DOMAIN));
>         ut_assertok(sandbox_power_domain_test_get(dev_test));
>
>
> --
> 2.47.0
>

Regards,
SImon