Re: [PATCH v4 00/15] acpi/pwm/i915: Convert pwm-crc and i915 driver's PWM code to use the atomic PWM API

Hans de Goede
2020-07-09T14:41:17Z

Hi,

On 7/9/20 4:14 PM, Sam Ravnborg wrote:
> Hi Hans.
>
> On Wed, Jul 08, 2020 at 11:14:16PM +0200, Hans de Goede wrote:
>> Hi All,
>>
>> Here is v4 of my patch series converting the i915 driver's code for
>> controlling the panel's backlight with an external PWM controller to
>> use the atomic PWM API. See below for the changelog.
>
> Why is it that i915 cannot use the pwm_bl driver for backlight?
> I have not studied the code - just wondering.

The intel_panel.c code deals with 7 different types of PWM controllers
which are built into the GPU + support for external PWM controllers
through the kernel's PWM subsystem.

pwm_bl will work for the external PWM controller case, but not for
the others. On top of that the intel_panel code integrates which
the video BIOS, getting things like frequency, minimum value
and if the range is inverted (0% duty == backlight brightness max).
I'm not even sure if pwm_bl supports all of this, but even if it
does the intel_panel code handles this in a unified manner for
all supported PWM controllers, including the ones which are
an integral part of the GPU.

Regards,

Hans

>> Initially the plan was for this series to consist of 2 parts:
>> 1. convert the pwm-crc driver to support the atomic PWM API and
>> 2. convert the i915 driver's PWM code to use the atomic PWM API.
>>
>> But during testing I've found a number of bugs in the pwm-lpss and I
>> found that the acpi_lpss code needs some special handling because of
>> some ugliness found in most Cherry Trail DSDTs.
>>
>> So now this series has grown somewhat large and consists of 4 parts:
>>
>> 1. acpi_lpss fixes workarounds for Cherry Trail DSTD nastiness
>> 2. various fixes to the pwm-lpss driver
>> 3. convert the pwm-crc driver to support the atomic PWM API and
>> 4. convert the i915 driver's PWM code to use the atomic PWM API
>>
>> The involved acpi_lpss and pwm drivers do not see a whole lot of churn,
>> so the plan is to merge this all through drm-intel-next-queued (dinq)
>> once all the patches are reviewed / have acks.
>>
>> In v4 the ACPI patches have been Acked by Rafael and the i915 patches
>> have been acked by Jani. So that just leaves the PWM patches.
>>
>> Uwe can I get your ok / ack for merging this through the dinq branch
>> once you have acked al the PWM patches ?
>>
>> This series has been tested (and re-tested after adding various bug-fixes)
>> extensively. It has been tested on the following devices:
>>
>> -Asus T100TA BYT + CRC-PMIC PWM
>> -Toshiba WT8-A BYT + CRC-PMIC PWM
>> -Thundersoft TS178 BYT + CRC-PMIC PWM, inverse PWM
>> -Asus T100HA CHT + CRC-PMIC PWM
>> -Terra Pad 1061 BYT + LPSS PWM
>> -Trekstor Twin 10.1 BYT + LPSS PWM
>> -Asus T101HA CHT + CRC-PMIC PWM
>> -GPD Pocket CHT + CRC-PMIC PWM
>>
>> Changelog:
>>
>> Changes in v2:
>> - Fix coverletter subject
>> - Drop accidentally included debugging patch
>> - "[PATCH v3 02/15] ACPI / LPSS: Save Cherry Trail PWM ctx registers only once (
>> - Move #define LPSS_SAVE_CTX_ONCE define to group it with LPSS_SAVE_CTX
>>
>> Changes in v3:
>> - "[PATCH v3 04/15] pwm: lpss: Add range limit check for the base_unit register value"
>> - Use base_unit_range - 1 as maximum value for the clamp()
>> - "[PATCH v3 05/15] pwm: lpss: Use pwm_lpss_apply() when restoring state on resume"
>> - This replaces the "pwm: lpss: Set SW_UPDATE bit when enabling the PWM"
>> patch from previous versions of this patch-set, which really was a hack
>> working around the resume issue which this patch fixes properly.
>> - PATCH v3 6 - 11 pwm-crc changes:
>> - Various small changes resulting from the reviews by Andy and Uwe,
>> including some refactoring of the patches to reduce the amount of churn
>> in the patch-set
>>
>> Changes in v4:
>> - "[PATCH v4 06/16] pwm: lpss: Correct get_state result for base_unit == 0"
>> - This is a new patch in v4 of this patchset
>> - "[PATCH v4 12/16] pwm: crc: Implement get_state() method"
>> - Use DIV_ROUND_UP when calculating the period and duty_cycle values
>> - "[PATCH v4 16/16] drm/i915: panel: Use atomic PWM API for devs with an external PWM controller"
>> - Add a note to the commit message about the changes in pwm_disable_backlight()
>> - Use the pwm_set/get_relative_duty_cycle() helpers
>>
>> Regards,
>>
>> Hans
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>