Re: [PATCH v2] drm/i915/display: Add quirk to force backlight type on some TUXEDO devices

[Werner Sembach <wse@tuxedocomputers.com>]

Hi Suraj,

Am 29.01.26 um 05:23 schrieb Kandpal, Suraj:
>> Subject: [PATCH v2] drm/i915/display: Add quirk to force backlight type on
>> some TUXEDO devices
>>
>> The display backlight on TUXEDO DX1708 and InsanityBook 15 v1 with panels
>> AUO 12701 and AUO 12701 must be forced to
>> INTEL_DP_AUX_BACKLIGHT_ON to be able to control the brightness.
>>
>> This could already be archived via a module parameter, but this patch adds a
>> quirk to apply this by default on the mentioned devices.
>>
>> This patch does not actually test for the exact panels as the id that is used in
>> the intel_dpcd_quirks list is sadly zeroed on the devices, but afaik all these
>> devices use try_intel_interface first anyway so all the quirk does is to add the
>> fallback to try_vesa_interface, so the behaviour on the devices not needing
>> the quirk and fallback should functionally stay the same.
> Hi Sembach,
>
> Thanks for the patch. I would recommend opening a gitlab issue with all the details
> (platform, edp version etc), Along with dmesg logs with drm.debug set to 0x10e and kernel
> Version mentioned . So we can root cause this properly and determine is an actual quirk is required or not.
> Use can use this as a guide https://drm.pages.freedesktop.org/intel-docs/how-to-file-i915-bugs.html

Done: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/15679

Best Regards,

Werner

>
> Regards,
> Suraj Kandpal
>
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Werner Sembach <wse@tuxedocomputers.com>
>> ---
>>   .../drm/i915/display/intel_dp_aux_backlight.c |  9 ++++++-
>>   drivers/gpu/drm/i915/display/intel_quirks.c   | 25 ++++++++++++++++++-
>>   drivers/gpu/drm/i915/display/intel_quirks.h   |  1 +
>>   3 files changed, 33 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
>> b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
>> index 0a3a3f6a5f9d8..bbdfa142d084d 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
>> @@ -41,6 +41,7 @@
>>   #include "intel_display_types.h"
>>   #include "intel_dp.h"
>>   #include "intel_dp_aux_backlight.h"
>> +#include "intel_quirks.h"
>>
>>   /*
>>    * DP AUX registers for Intel's proprietary HDR backlight interface. We define
>> @@ -661,11 +662,17 @@ int intel_dp_aux_init_backlight_funcs(struct
>> intel_connector *connector)
>>   	struct drm_device *dev = connector->base.dev;
>>   	struct intel_panel *panel = &connector->panel;
>>   	bool try_intel_interface = false, try_vesa_interface = false;
>> +	int enable_dpcd_backlight;
>>
>>   	/* Check the VBT and user's module parameters to figure out which
>>   	 * interfaces to probe
>>   	 */
>> -	switch (display->params.enable_dpcd_backlight) {
>> +	enable_dpcd_backlight = display->params.enable_dpcd_backlight;
>> +	if (enable_dpcd_backlight == INTEL_DP_AUX_BACKLIGHT_AUTO &&
>> +	    intel_has_dpcd_quirk(intel_dp,
>> QUIRK_ENABLE_DPCD_BACKLIGHT))
>> +		enable_dpcd_backlight = INTEL_DP_AUX_BACKLIGHT_ON;
>> +
>> +	switch (enable_dpcd_backlight) {
>>   	case INTEL_DP_AUX_BACKLIGHT_OFF:
>>   		return -ENODEV;
>>   	case INTEL_DP_AUX_BACKLIGHT_AUTO:
>> diff --git a/drivers/gpu/drm/i915/display/intel_quirks.c
>> b/drivers/gpu/drm/i915/display/intel_quirks.c
>> index d2e16b79d6be1..df20930f73f75 100644
>> --- a/drivers/gpu/drm/i915/display/intel_quirks.c
>> +++ b/drivers/gpu/drm/i915/display/intel_quirks.c
>> @@ -86,6 +86,14 @@ static void quirk_edp_limit_rate_hbr2(struct
>> intel_display *display)
>>   	drm_info(display->drm, "Applying eDP Limit rate to HBR2 quirk\n");  }
>>
>> +static void quirk_enable_dpcd_backlight(struct intel_dp *intel_dp) {
>> +	struct intel_display *display = to_intel_display(intel_dp);
>> +
>> +	intel_set_dpcd_quirk(intel_dp, QUIRK_ENABLE_DPCD_BACKLIGHT);
>> +	drm_info(display->drm, "Applying Enable DPCD Backlight quirk\n"); }
>> +
>>   struct intel_quirk {
>>   	int device;
>>   	int subsystem_vendor;
>> @@ -251,7 +259,22 @@ static const struct intel_dpcd_quirk
>> intel_dpcd_quirks[] = {
>>   		.sink_oui = SINK_OUI(0x38, 0xec, 0x11),
>>   		.hook = quirk_fw_sync_len,
>>   	},
>> -
>> +	/* TUXEDO InsanityBook 15 v1 */
>> +	{
>> +		.device = 0x591b,
>> +		.subsystem_vendor = 0x1558,
>> +		.subsystem_device = 0x9501,
>> +		.sink_oui = SINK_OUI(0x38, 0xec, 0x11),
>> +		.hook = quirk_enable_dpcd_backlight,
>> +	},
>> +	/* TUXEDO DX1708 */
>> +	{
>> +		.device = 0x3e9b,
>> +		.subsystem_vendor = 0x1558,
>> +		.subsystem_device = 0x8500,
>> +		.sink_oui = SINK_OUI(0x38, 0xec, 0x11),
>> +		.hook = quirk_enable_dpcd_backlight,
>> +	},
>>   };
>>
>>   void intel_init_quirks(struct intel_display *display) diff --git
>> a/drivers/gpu/drm/i915/display/intel_quirks.h
>> b/drivers/gpu/drm/i915/display/intel_quirks.h
>> index 06da0e286c67c..686f306ab4472 100644
>> --- a/drivers/gpu/drm/i915/display/intel_quirks.h
>> +++ b/drivers/gpu/drm/i915/display/intel_quirks.h
>> @@ -21,6 +21,7 @@ enum intel_quirk_id {
>>   	QUIRK_NO_PPS_BACKLIGHT_POWER_HOOK,
>>   	QUIRK_FW_SYNC_LEN,
>>   	QUIRK_EDP_LIMIT_RATE_HBR2,
>> +	QUIRK_ENABLE_DPCD_BACKLIGHT,
>>   };
>>
>>   void intel_init_quirks(struct intel_display *display);
>> --
>> 2.43.0