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Subject: Re: [PATCH 2/3] mfd: intel_soc_pmic: Rename pwm_backlight pwm-lookup
 to pwm_pmic_backlight
To:     Lee Jones <lee.jones@linaro.org>
Cc:     Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        =?UTF-8?B?VmlsbGUgU3lyasOkbMOk?= <ville.syrjala@linux.intel.com>,
        "Rafael J . Wysocki" <rjw@rjwysocki.net>,
        Len Brown <lenb@kernel.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        linux-acpi@vger.kernel.org,
        intel-gfx <intel-gfx@lists.freedesktop.org>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
References: <20191119151818.67531-1-hdegoede@redhat.com>
 <20191119151818.67531-3-hdegoede@redhat.com> <20191210085111.GQ3468@dell>
 <a05e5a2b-568e-2b0d-0293-aa937c590a74@redhat.com>
 <20191212084546.GA3468@dell>
From:   Hans de Goede <hdegoede@redhat.com>
Message-ID: <d22e9a04-da09-0f41-a78e-ac17a947650a@redhat.com>
Date:   Thu, 12 Dec 2019 15:34:33 +0100
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Hi,

On 12-12-2019 09:45, Lee Jones wrote:
> On Wed, 11 Dec 2019, Hans de Goede wrote:
> 
>> Hi Lee,
>>
>> On 10-12-2019 09:51, Lee Jones wrote:
>>> On Tue, 19 Nov 2019, Hans de Goede wrote:
>>>
>>>> At least Bay Trail (BYT) and Cherry Trail (CHT) devices can use 1 of 2
>>>> different PWM controllers for controlling the LCD's backlight brightness.
>>>>
>>>> Either the one integrated into the PMIC or the one integrated into the
>>>> SoC (the 1st LPSS PWM controller).
>>>>
>>>> So far in the LPSS code on BYT we have skipped registering the LPSS PWM
>>>> controller "pwm_backlight" lookup entry when a Crystal Cove PMIC is
>>>> present, assuming that in this case the PMIC PWM controller will be used.
>>>>
>>>> On CHT we have been relying on only 1 of the 2 PWM controllers being
>>>> enabled in the DSDT at the same time; and always registered the lookup.
>>>>
>>>> So far this has been working, but the correct way to determine which PWM
>>>> controller needs to be used is by checking a bit in the VBT table and
>>>> recently I've learned about 2 different BYT devices:
>>>> Point of View MOBII TAB-P800W
>>>> Acer Switch 10 SW5-012
>>>>
>>>> Which use a Crystal Cove PMIC, yet the LCD is connected to the SoC/LPSS
>>>> PWM controller (and the VBT correctly indicates this), so here our old
>>>> heuristics fail.
>>>>
>>>> Since only the i915 driver has access to the VBT, this commit renames
>>>> the "pwm_backlight" lookup entries for the Crystal Cove PMIC's PWM
>>>> controller to "pwm_pmic_backlight" so that the i915 driver can do a
>>>> pwm_get() for the right controller depending on the VBT bit, instead of
>>>> the i915 driver relying on a "pwm_backlight" lookup getting registered
>>>> which magically points to the right controller.
>>>>
>>>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>>>> ---
>>>>    drivers/mfd/intel_soc_pmic_core.c | 2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> For my own reference:
>>>     Acked-for-MFD-by: Lee Jones <lee.jones@linaro.org>
>>
>> As mentioned in the cover-letter, to avoid breaking bi-sectability
>> as well as to avoid breaking the intel-gfx CI we need to merge this series
>> in one go through one tree. Specifically through the drm-intel tree.
>> Is that ok with you ?
>>
>> If this is ok with you, then you do not have to do anything, I will just push
>> the entire series to drm-intel. drivers/mfd/intel_soc_pmic_core.c
>> does not see much changes so I do not expect this to lead to any conflicts.
> 
> It's fine, so long as a minimal immutable pull-request is provided.
> Whether it's pulled or not will depend on a number of factors, but it
> needs to be an option.

The way the drm subsys works that is not really a readily available
option. The struct definition which this patch changes a single line in
has not been touched since 2015-06-26 so I really doubt we will get a
conflict from this.

Regards,

Hans