Re: [PATCH 5/9] pinctrl: samsung: Move retention control from mach-exynos to the pinctrl driver

[Marek Szyprowski <m.szyprowski@samsung.com>]

Hi Tomasz,


On 2016-12-26 06:55, Tomasz Figa wrote:
> 2016-12-23 21:24 GMT+09:00 Marek Szyprowski <m.szyprowski@samsung.com>:
>> Pad retention control after suspend/resume cycle should be done from pin
>> controller driver instead of PMU (power management unit) driver to avoid
>> possible ordering and logical dependencies. Till now it worked fine only
>> because PMU driver registered its sys_ops after pin controller.
>>
>> This patch moves pad retention control from PMU driver to Exynos pin
>> controller driver. This is a preparation for adding new features to Exynos
>> pin controller driver, like runtime power management and suspending
>> individual pin controllers, which might be a part of some power domain.
>>
> It looks like this change will essentially break the compatibility
> with DTBs that don't have the pmu syscon specified in pin controller
> nodes.
>
> On the other hand, moving this code to where it actually belongs
> really makes sense, so maybe we could just avoid the need of having
> this property, by looking up the PMU manually, by hardcoded string or
> so, if the proper property is not present?

Well, once again the topic of mythical device tree compatibility appearch.

There are imho following possibilities:

1. https://patchwork.kernel.org/patch/9477963/ ("Explicitly mark Samsung
    Exynos SoC bindings as unstable"), simply apply this approach and ignore
    users, who don't update their device tree blobs (are there any??).

2. Switch to syscon_regmap_lookup_by_compatible() lookup and hardcode PMU
    compatible id for all Exynos SoCs in the pin control driver. Then maybe,
    while unifying the code, switch other Exynos drivers to this approach
    and remove PMU phandles from device tree to make the code a bit more
    consistent across drivers and easier to understand.

3. Mixed approach, which combines drawbacks of both approaches. Additional
    dead code for handling mythical compatibility and harder to understand
    relations between the drivers.


> [...]
>
>> diff --git a/Documentation/devicetree/bindings/pinctrl/samsung-pinctrl.txt b/Documentation/devicetree/bindings/pinctrl/samsung-pinctrl.txt
>> index 1baf19eecabf..b7bd2e12a269 100644
>> --- a/Documentation/devicetree/bindings/pinctrl/samsung-pinctrl.txt
>> +++ b/Documentation/devicetree/bindings/pinctrl/samsung-pinctrl.txt
>> @@ -43,6 +43,10 @@ Required Properties:
>>                  };
>>          };
>>
>> +- samsung,pmu-syscon: Phandle to the PMU system controller, to let driver
>> +  to control pad retention after system suspend/resume cycle (only for Exynos
>> +  SoC series).
>> +
> Ah, here it is. I think adding relevant binding documentation at the
> beginning of the series would make it much easier for reviewers to
> understand the change.

I already pointed that patches are ordered to make the changes 
bisectable, what
usually means that new properties are added first, before being required 
by the
drivers.

>
>>   - Pin banks as child nodes: Pin banks of the controller are represented by child
>>     nodes of the controller node. Bank name is taken from name of the node. Each
>>     bank node must contain following properties:
> [...]
>
>> +static void exynos_retention_audio_off(struct samsung_pinctrl_drv_data *drvdata)
>> +{
>> +       if (!IS_ERR(pmu_regs))
> nit: Negated conditions make the code more difficult to read. Also it
> would be consistent with exynos_retention_off() to just bail out if
> (IS_ERR(pmu_regs)).
>
>> +               regmap_write(pmu_regs, S5P_PAD_RET_MAUDIO_OPTION,
>> +                            EXYNOS_WAKEUP_FROM_LOWPWR);
>> +}
> [...]
>
>> @@ -1139,15 +1146,15 @@ static void samsung_pinctrl_suspend_dev(
>>
>>          if (drvdata->suspend)
>>                  drvdata->suspend(drvdata);
>> +       if (drvdata->retention_on)
>> +               drvdata->retention_on(drvdata);
>> +
> nit: Unnecessary blank line.
>
> Best regards,
> Tomasz
>
>
>

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland