Re: [PATCH] drm/panfrost: Fix regulator_get_optional() misuse

[Steven Price]

On 09/09/2019 16:41, Rob Herring wrote:
> On Fri, Sep 6, 2019 at 4:23 PM Steven Price <steven.price@xxxxxxx> wrote:
>>
>> On 04/09/2019 13:30, Mark Brown wrote:
>>> The panfrost driver requests a supply using regulator_get_optional()
>>> but both the name of the supply and the usage pattern suggest that it is
>>> being used for the main power for the device and is not at all optional
>>> for the device for function, there is no meaningful handling for absent
>>> supplies.  Such regulators should use the vanilla regulator_get()
>>> interface, it will ensure that even if a supply is not described in the
>>> system integration one will be provided in software.
>>>
>>> Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
>>
>> Tested-by: Steven Price <steven.price@xxxxxxx>
>>
>> Looks like my approach to this was wrong - so we should also revert the
>> changes I made previously.
>>
>> ----8<----
>> From fe20f8abcde8444bb41a8f72fb35de943a27ec5c Mon Sep 17 00:00:00 2001
>> From: Steven Price <steven.price@xxxxxxx>
>> Date: Fri, 6 Sep 2019 15:20:53 +0100
>> Subject: [PATCH] drm/panfrost: Revert changes to cope with NULL regulator
>>
>> Handling a NULL return from devm_regulator_get_optional() doesn't seem
>> like the correct way of handling this. Instead revert the changes in
>> favour of switching to using devm_regulator_get() which will return a
>> dummy regulator instead.
>>
>> Reverts commit 52282163dfa6 ("drm/panfrost: Add missing check for pfdev->regulator")
>> Reverts commit e21dd290881b ("drm/panfrost: Enable devfreq to work without regulator")
> 
> Does a straight revert of these 2 patches not work? If it does work,
> can you do that and send to the list. I don't want my hand slapped
> again reverting things.

I wasn't sure what was best here - 52282163dfa6 is a bug fix, so
reverting that followed by e21dd290881b would (re-)introduce a
regression for that one commit (i.e. not completely bisectable).
Reverting in the other order would work, but seems a little odd.
Squashing the reverts seemed the neatest option - but it's not my hand
at risk... :)

Perhaps it would be best to simply apply Mark's change followed by
something like the following. That way it's not actually a revert!
It also avoids (re-)adding the now redundant check in
panfrost_devfreq_init().

Steve

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