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
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