Re: [PATCH] pinctrl: Enforce device links

[Benjamin GAIGNARD <benjamin.gaignard@xxxxxx>]

On 12/12/19 11:56 AM, Ulf Hansson wrote:
> + Benjamin
>
> On Thu, 12 Dec 2019 at 11:11, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
>> Instead of opt-in device links, enforce it across the board.
>> Everyone probably needs this anyway, lest runtime[_pm] suspend
>> order will be haphazard.
>>
>> Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
>> Cc: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
>> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
>> ---
>> As there is no progress on opting in drivers for this we can just
>> enforce it.
>>
>> I am a bit concerned that with every pin control state change the
>> link reference count will just go up, but does it really matter?
>> ---
>>   drivers/pinctrl/core.c                | 25 ++++++++++++++-----------
>>   drivers/pinctrl/pinctrl-stmfx.c       |  1 -
>>   drivers/pinctrl/stm32/pinctrl-stm32.c |  1 -
>>   include/linux/pinctrl/pinctrl.h       |  5 -----
>>   4 files changed, 14 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c
>> index 2bbd8ee93507..1d2cdeebb316 100644
>> --- a/drivers/pinctrl/core.c
>> +++ b/drivers/pinctrl/core.c
>> @@ -1220,15 +1220,6 @@ struct pinctrl_state *pinctrl_lookup_state(struct pinctrl *p,
>>   }
>>   EXPORT_SYMBOL_GPL(pinctrl_lookup_state);
>>
>> -static void pinctrl_link_add(struct pinctrl_dev *pctldev,
>> -                            struct device *consumer)
>> -{
>> -       if (pctldev->desc->link_consumers)
>> -               device_link_add(consumer, pctldev->dev,
>> -                               DL_FLAG_PM_RUNTIME |
>> -                               DL_FLAG_AUTOREMOVE_CONSUMER);
>> -}
>> -
>>   /**
>>    * pinctrl_commit_state() - select/activate/program a pinctrl state to HW
>>    * @p: the pinctrl handle for the device that requests configuration
>> @@ -1276,8 +1267,20 @@ static int pinctrl_commit_state(struct pinctrl *p, struct pinctrl_state *state)
>>                  }
>>
>>                  /* Do not link hogs (circular dependency) */
>> -               if (p != setting->pctldev->p)
>> -                       pinctrl_link_add(setting->pctldev, p->dev);
>> +               if (p != setting->pctldev->p) {
>> +                       /*
>> +                        * Create a device link to the consumer such that
>> +                        * it will enforce that runtime PM suspend/resume
>> +                        * is done first on consumers before we get to
>> +                        * the pin controller itself. As some devices get
>> +                        * their pin control state even before probe() it is
>> +                        * important to use DL_FLAG_AUTOREMOVE_CONSUMER.
>> +                        */
>> +                       device_link_add(p->dev,
>> +                                       setting->pctldev->dev,
>> +                                       DL_FLAG_PM_RUNTIME |
>> +                                       DL_FLAG_AUTOREMOVE_CONSUMER);
> I understand DL_FLAG_PM_RUNTIME is used even prior $subject patch, but
> could you please explain some of the reasons behind that?
>
> In regards to adding a new link every time you commit/select a new
> state, that sounds wrong to me. Why are we doing this?

If a link already exists it will not add new one so it safe for me.

>
> Instead, don't you want to add a link when the consumer looks up the
> pinctrl cookie/handle (devm_pinctrl_get()), thus when create_pinctrl()
> is called?
Because it was the only place I add found where I get a the same
time pointers on the consumer and the producer devices.

>
> Additionally, I didn't find any place where the link is removed. I
> looks like that should happen when the consumer drops the reference
> for the pinctrl cookie, no?

The link is automatically removed when the consumer device is deleted

thanks to DL_FLAG_AUTOREMOVE_CONSUMER flag.

Benjamin

>
>> +               }
>>          }
>>
>>          p->state = state;
>> diff --git a/drivers/pinctrl/pinctrl-stmfx.c b/drivers/pinctrl/pinctrl-stmfx.c
>> index 16723797fa7c..4306b8444188 100644
>> --- a/drivers/pinctrl/pinctrl-stmfx.c
>> +++ b/drivers/pinctrl/pinctrl-stmfx.c
>> @@ -638,7 +638,6 @@ static int stmfx_pinctrl_probe(struct platform_device *pdev)
>>          pctl->pctl_desc.pins = stmfx_pins;
>>          pctl->pctl_desc.npins = ARRAY_SIZE(stmfx_pins);
>>          pctl->pctl_desc.owner = THIS_MODULE;
>> -       pctl->pctl_desc.link_consumers = true;
>>
>>          ret = devm_pinctrl_register_and_init(pctl->dev, &pctl->pctl_desc,
>>                                               pctl, &pctl->pctl_dev);
>> diff --git a/drivers/pinctrl/stm32/pinctrl-stm32.c b/drivers/pinctrl/stm32/pinctrl-stm32.c
>> index 2d5e0435af0a..ec59a58600ce 100644
>> --- a/drivers/pinctrl/stm32/pinctrl-stm32.c
>> +++ b/drivers/pinctrl/stm32/pinctrl-stm32.c
>> @@ -1439,7 +1439,6 @@ int stm32_pctl_probe(struct platform_device *pdev)
>>          pctl->pctl_desc.owner = THIS_MODULE;
>>          pctl->pctl_desc.pins = pins;
>>          pctl->pctl_desc.npins = pctl->npins;
>> -       pctl->pctl_desc.link_consumers = true;
>>          pctl->pctl_desc.confops = &stm32_pconf_ops;
>>          pctl->pctl_desc.pctlops = &stm32_pctrl_ops;
>>          pctl->pctl_desc.pmxops = &stm32_pmx_ops;
>> diff --git a/include/linux/pinctrl/pinctrl.h b/include/linux/pinctrl/pinctrl.h
>> index 7ce23450a1cb..c6159f041f4e 100644
>> --- a/include/linux/pinctrl/pinctrl.h
>> +++ b/include/linux/pinctrl/pinctrl.h
>> @@ -122,10 +122,6 @@ struct pinctrl_ops {
>>    *     the hardware description
>>    * @custom_conf_items: Information how to print @params in debugfs, must be
>>    *     the same size as the @custom_params, i.e. @num_custom_params
>> - * @link_consumers: If true create a device link between pinctrl and its
>> - *     consumers (i.e. the devices requesting pin control states). This is
>> - *     sometimes necessary to ascertain the right suspend/resume order for
>> - *     example.
>>    */
>>   struct pinctrl_desc {
>>          const char *name;
>> @@ -140,7 +136,6 @@ struct pinctrl_desc {
>>          const struct pinconf_generic_params *custom_params;
>>          const struct pin_config_item *custom_conf_items;
>>   #endif
>> -       bool link_consumers;
>>   };
>>
>>   /* External interface to pin controller */
>> --
>> 2.23.0
>>
> Kind regards
> Uffe