[v7,3/6] clk: qcom: gdsc: Add a reset op to poll gdsc collapse

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).

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(-)

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.

>
> 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).

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

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

On 12/8/2022 8:32 PM, Akhil P Oommen wrote:
> 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.
Btw, we can optimize this a bit more using 'completion' to minimize CPU overhead. But that can wait as this is supposed to be a rarely used path. We don't expect gpu faults often. I would like to see a simpler implementation upstream first.

-Akhil.
>>
>>>         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