Created attachment 144941 [details]
drm-tip dmesg with drm.debug=0x1e from Lenovo Miix 320-10ICR
I find that brightness adjustment is broken on Lenovo Miix 320-10ICR since Linux 5.3rc1, git bisect lead to this commit:
drm-tip 2019-07-30 4040b4c4ab647422d82100c8b091d34b6a82f572 log with drm.debug=0x1e log_buf_len=8M where I trying to adjust brightness is attached.
Brightness adjustment works fine on Linux 5.0-5.2 (earlies releases wasn't tested).
You should definitely mention what interface you are using to change the backlight.
On Linux 5.0-5.2 I adjusted backlight via Gnome Shell slider in upper right corner. On Linux 5.3rc1+ this is no longer works, according to git bisect this is due to mentioned commit. That all I know right now.
If I can provide more data from working/mom-working kernel - please let me know how to do so.
[7.984343] [drm:intel_panel_vbt_fixed_mode [i915]] [CONNECTOR:105:DSI-1] using mode from VBT:
[ 7.984387] [drm:drm_mode_debug_printmodeline [drm]] Modeline "1200x1920": 0 162980 1200 1280 1284 1344 1920 1980 1981 2021 0x8 0xa
[ 7.984494] [drm:pwm_setup_backlight [i915]] *ERROR* Failed to own the pwm chip
[ 7.984600] [drm:intel_panel_setup_backlight [i915]] failed to setup backlight for connector DSI-1
[ 7.984698] [drm:intel_dsi_get_hw_state [i915]]
[ 7.984922] [drm:intel_modeset_readout_hw_state [i915]] [CRTC:47:pipe A] hw state readout: enabled
@Chris, any suggestion here? Does this error give any clue?
Two drivers for one bit of backlight HW, doomed to fail.
If the acpi driver exposed a /sys/class/backlight, xf86-video-intel should have still found it.
Created attachment 144959 [details]
drm-tip dmesg with drm.debug=0x1e from Lenovo Miix2 8
As I just found same issue is reproducible on Lenovo Miix2 8 too.
Attached log is from drm-tip 2019-08-05 (2bb7df95d4e058e61d9de39f1b97404592708d24)
> If the acpi driver exposed a /sys/class/backlight, xf86-video-intel should have still found it.
Lenovo Miix2 8, Lenovo Miix 320-10IRC
On Linux 5.2 there is just one intel_backlight, adjusting brightness via intel_backlight works.
Lenovo Miix2 8:
On Linux 5.3 there is acpi_video0 and acpi_video1, echo values to brightness file in each one doesn't change backlight level.
Lenovo Miix 320-10IRC:
On Linux 5.3 there is...
~# ls /sys/class/backlight
acpi_video0 acpi_video1 acpi_video2 acpi_video3 acpi_video4 acpi_video5 acpi_video6 acpi_video7
As with Lenovo Miix2 8, echo values to brightness file in each acpi_video doesn't change backlight level.
For comparison below is logs from Linux 5.2.7 with drm.debug=0x1e and working backlight adjustment:
Created attachment 144972 [details]
Linux 5.2.7 dmesg with drm.debug=0x1e from Lenovo Miix 320-10ICR
Created attachment 144973 [details]
Linux 5.2.7 dmesg with drm.debug=0x1e from Lenovo Miix2 8
Cc Thierry, committer of the regressing commit
Author: Nikolaus Voss <email@example.com>
Date: Wed Jun 12 10:36:07 2019 +0200
pwm: Add support referencing PWMs from ACPI
Per Thierry, the fix is , on its way to v5.3-rc4. Thanks for the report, closing. Please reopen if the problem persists with that commit.
Issue is no longer reproducible with Linux 5.3rc4.