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Message-ID: <9726a08f-266e-2949-8141-3a726ffd2795@quicinc.com>
Date:   Thu, 8 Dec 2022 20:32:57 +0530
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Subject: Re: [PATCH v7 3/6] clk: qcom: gdsc: Add a reset op to poll gdsc
 collapse
Content-Language: en-US
To:     Ulf Hansson <ulf.hansson@linaro.org>
CC:     freedreno <freedreno@lists.freedesktop.org>,
        <dri-devel@lists.freedesktop.org>, <linux-arm-msm@vger.kernel.org>,
        Rob Clark <robdclark@gmail.com>,
        Bjorn Andersson <andersson@kernel.org>,
        Stephen Boyd <swboyd@chromium.org>,
        Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Douglas Anderson <dianders@chromium.org>,
        <krzysztof.kozlowski@linaro.org>, Andy Gross <agross@kernel.org>,
        Konrad Dybcio <konrad.dybcio@somainline.org>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>, <linux-clk@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
References: <1664960824-20951-1-git-send-email-quic_akhilpo@quicinc.com>
 <20221005143618.v7.3.I162c4be55f230cd439f0643f1624527bdc8a9831@changeid>
 <CAPDyKFpMUQo-Q2sbm3YXPeagt88zsRFWgc06GmNm0TVUPmPY_g@mail.gmail.com>
From:   Akhil P Oommen <quic_akhilpo@quicinc.com>
In-Reply-To: <CAPDyKFpMUQo-Q2sbm3YXPeagt88zsRFWgc06GmNm0TVUPmPY_g@mail.gmail.com>
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On 12/7/2022 9:15 PM, Ulf Hansson wrote:
> On Wed, 5 Oct 2022 at 11:08, Akhil P Oommen <quic_akhilpo@quicinc.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.

https://patchwork.freedesktop.org/patch/498397/
gpu driver side changes are already merged in upstream. We call this interface during a GPU recovery which is supposed to be a rare event.
>
>> Signed-off-by: Akhil P Oommen <quic_akhilpo@quicinc.com>
>> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.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).
I was going for a minimal code churn to get this mainlined easily. I like the idea, perhaps we can have a refactor patch if there is consensus.

-Akhil.
>
> 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