Date:   Wed, 7 Dec 2022 16:45:34 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Akhil P Oommen <quic_akhilpo@...cinc.com>
Cc:     freedreno <freedreno@...ts.freedesktop.org>,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        Rob Clark <robdclark@...il.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Douglas Anderson <dianders@...omium.org>,
        krzysztof.kozlowski@...aro.org, Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 3/6] clk: qcom: gdsc: Add a reset op to poll gdsc collapse

On Wed, 5 Oct 2022 at 11:08, Akhil P Oommen <quic_akhilpo@...cinc.com> wrote:
>
> Add a reset op compatible function to poll for gdsc collapse. This is
> required because:
>   1. We don't wait for it to turn OFF at hardware for VOTABLE GDSCs.
>   2. There is no way for client drivers (eg. gpu driver) to do
>   put-with-wait for these gdscs which is required in some scenarios
>   (eg. GPU recovery).

What puzzles me a bit, who is the typical consumer of the reset.

I looked at patch4 and tried to figure it out, but let's discuss that
in that thread instead. Some more comments, see below.

>
> Signed-off-by: Akhil P Oommen <quic_akhilpo@...cinc.com>
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> ---
>
> Changes in v7:
> - Update commit message (Bjorn)
>
> Changes in v2:
> - Minor update to function prototype
>
>  drivers/clk/qcom/gdsc.c | 23 +++++++++++++++++++----
>  drivers/clk/qcom/gdsc.h |  7 +++++++
>  2 files changed, 26 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c
> index 7cf5e13..ccef742 100644
> --- a/drivers/clk/qcom/gdsc.c
> +++ b/drivers/clk/qcom/gdsc.c
> @@ -17,6 +17,7 @@
>  #include <linux/reset-controller.h>
>  #include <linux/slab.h>
>  #include "gdsc.h"
> +#include "reset.h"
>
>  #define PWR_ON_MASK            BIT(31)
>  #define EN_REST_WAIT_MASK      GENMASK_ULL(23, 20)
> @@ -116,7 +117,8 @@ static int gdsc_hwctrl(struct gdsc *sc, bool en)
>         return regmap_update_bits(sc->regmap, sc->gdscr, HW_CONTROL_MASK, val);
>  }
>
> -static int gdsc_poll_status(struct gdsc *sc, enum gdsc_status status)
> +static int gdsc_poll_status(struct gdsc *sc, enum gdsc_status status,
> +               s64 timeout_us, unsigned int interval_ms)
>  {
>         ktime_t start;
>
> @@ -124,7 +126,9 @@ static int gdsc_poll_status(struct gdsc *sc, enum gdsc_status status)
>         do {
>                 if (gdsc_check_status(sc, status))
>                         return 0;
> -       } while (ktime_us_delta(ktime_get(), start) < TIMEOUT_US);
> +               if (interval_ms)
> +                       msleep(interval_ms);
> +       } while (ktime_us_delta(ktime_get(), start) < timeout_us);

Rather than continue to open code this polling loop, would it not make
sense to convert the code into using readx_poll_timeout() (or some of
its friends).

Down the road, this leads to that the msleep() above should become
usleep_range() instead, which seems more correct to me.

>
>         if (gdsc_check_status(sc, status))
>                 return 0;
> @@ -189,7 +193,7 @@ static int gdsc_toggle_logic(struct gdsc *sc, enum gdsc_status status)
>                 udelay(1);
>         }
>
> -       ret = gdsc_poll_status(sc, status);
> +       ret = gdsc_poll_status(sc, status, TIMEOUT_US, 0);
>         WARN(ret, "%s status stuck at 'o%s'", sc->pd.name, status ? "ff" : "n");
>
>         if (!ret && status == GDSC_OFF && sc->rsupply) {
> @@ -360,7 +364,7 @@ static int _gdsc_disable(struct gdsc *sc)
>                  */
>                 udelay(1);
>
> -               ret = gdsc_poll_status(sc, GDSC_ON);
> +               ret = gdsc_poll_status(sc, GDSC_ON, TIMEOUT_US, 0);
>                 if (ret)
>                         return ret;
>         }
> @@ -608,3 +612,14 @@ int gdsc_gx_do_nothing_enable(struct generic_pm_domain *domain)
>         return 0;
>  }
>  EXPORT_SYMBOL_GPL(gdsc_gx_do_nothing_enable);
> +
> +int gdsc_wait_for_collapse(void *priv)
> +{
> +       struct gdsc *sc = priv;
> +       int ret;
> +
> +       ret = gdsc_poll_status(sc, GDSC_OFF, 500000, 5);
> +       WARN(ret, "%s status stuck at 'on'", sc->pd.name);
> +       return ret;
> +}
> +EXPORT_SYMBOL_GPL(gdsc_wait_for_collapse);
> diff --git a/drivers/clk/qcom/gdsc.h b/drivers/clk/qcom/gdsc.h
> index 981a12c..5395f69 100644
> --- a/drivers/clk/qcom/gdsc.h
> +++ b/drivers/clk/qcom/gdsc.h
> @@ -12,6 +12,7 @@
>  struct regmap;
>  struct regulator;
>  struct reset_controller_dev;
> +struct qcom_reset_map;
>
>  /**
>   * struct gdsc - Globally Distributed Switch Controller
> @@ -88,6 +89,7 @@ int gdsc_register(struct gdsc_desc *desc, struct reset_controller_dev *,
>                   struct regmap *);
>  void gdsc_unregister(struct gdsc_desc *desc);
>  int gdsc_gx_do_nothing_enable(struct generic_pm_domain *domain);
> +int gdsc_wait_for_collapse(void *priv);
>  #else
>  static inline int gdsc_register(struct gdsc_desc *desc,
>                                 struct reset_controller_dev *rcdev,
> @@ -97,5 +99,10 @@ static inline int gdsc_register(struct gdsc_desc *desc,
>  }
>
>  static inline void gdsc_unregister(struct gdsc_desc *desc) {};
> +
> +static int gdsc_wait_for_collapse(void *priv)
> +{
> +       return  -ENOSYS;
> +}
>  #endif /* CONFIG_QCOM_GDSC */
>  #endif /* __QCOM_GDSC_H__ */

Kind regards
Uffe

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