Re: [PATCH] drm/i915: keep backlight_enable on until turn eDP display off

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On Tue, 22 Jun 2021, 10:18 PM, Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> wrote:
>On Tue, 22 Jun 2021, Lee Shawn C <shawn.c.lee@xxxxxxxxx> wrote:
>> This workaround is specific for a particular panel on Google 
>> chromebook project. When user space daemon enter idle state.
>> It request adjust brightness to 0, turn backlight_enable signal off 
>> and keep eDP main link active.
>>
>> On general LCD, this behavior might not be a problem.
>> But on this panel, its tcon would expect source to execute full eDP 
>> power off sequence after drop backlight_enable signal.
>> Without eDP power off sequence. Even source try to turn 
>> backlight_enable signal on and restore proper brightness level.
>> This panel is not able to light on again.
>>
>> This WA ignored the request from user space daemon to disable 
>> backlight_enable signal and keep it on always. When user space request 
>> kernel to turn eDP display off, kernel driver still can control 
>> backlight_enable signal properly. It would not impact standard eDP 
>> power off sequence.
>>
>> Cc: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx>
>> Cc: Imre Deak <imre.deak@xxxxxxxxx>
>> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
>> Cc: Cooper Chiou <cooper.chiou@xxxxxxxxx>
>>
>> Signed-off-by: Lee Shawn C <shawn.c.lee@xxxxxxxxx>
>> ---
>>  drivers/gpu/drm/i915/display/intel_panel.c  |  4 ++-  
>> drivers/gpu/drm/i915/display/intel_quirks.c | 34 +++++++++++++++++++++
>>  drivers/gpu/drm/i915/i915_drv.h             |  1 +
>>  3 files changed, 38 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_panel.c 
>> b/drivers/gpu/drm/i915/display/intel_panel.c
>> index 7d7a60b4d2de..0212b53d932b 100644
>> --- a/drivers/gpu/drm/i915/display/intel_panel.c
>> +++ b/drivers/gpu/drm/i915/display/intel_panel.c
>> @@ -1311,6 +1311,7 @@ static void intel_panel_set_backlight(const 
>> struct drm_connector_state *conn_sta  static int 
>> intel_backlight_device_update_status(struct backlight_device *bd)  {
>>  	struct intel_connector *connector = bl_get_data(bd);
>> +	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
>>  	struct intel_panel *panel = &connector->panel;
>>  	struct drm_device *dev = connector->base.dev;
>>  
>> @@ -1330,7 +1331,8 @@ static int intel_backlight_device_update_status(struct backlight_device *bd)
>>  		if (panel->backlight.power) {
>>  			bool enable = bd->props.power == FB_BLANK_UNBLANK &&
>>  				bd->props.brightness != 0;
>> -			panel->backlight.power(connector, enable);
>> +			if (enable || !(dev_priv->quirks & QUIRK_KEEP_BACKLIGHT_ENABLE_ON))
>> +				panel->backlight.power(connector, enable);
>
>We'll want to avoid the hook altogether in this case, instead of complicating the logic even more. Something like:
>
>--- a/drivers/gpu/drm/i915/display/intel_dp.c
>+++ b/drivers/gpu/drm/i915/display/intel_dp.c
>@@ -5286,7 +5286,8 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
> 	}
> 
> 	intel_panel_init(&intel_connector->panel, fixed_mode, downclock_mode);
>-	intel_connector->panel.backlight.power = intel_pps_backlight_power;
>+	if (!(dev_priv->quirks & QUIRK_NO_PPS_BACKLIGHT_POWER_HOOK))
>+		intel_connector->panel.backlight.power = intel_pps_backlight_power;
> 	intel_panel_setup_backlight(connector, pipe);
> 
> 	if (fixed_mode) {
>
>---
>
>Please adjust the quirk name and debug logs accordingly.
>

Thanks! I will modify the quirk name and debug messages later.

>Truth be told I'd rather nuke the hook completely. But it was a request from Chrome to have this lightweight sub-state to black out the display, without mode set, using the panel power sequencer in cases where we can't set the backlight PWM to 0.
>
>Hmm. Is the brightness controlled using PWM or DPCD? We probably shouldn't do this at all when the brightness control is done using DPCD.

This panel refer to soc's backlight_enable signal to enable backlight. But adjust brightness via DPCD aux interface.
If source turn backlight_enable signal off, panel tcon await source execute full eDP power off sequence to disable local display.
And panel's backlight is not able to turn on again.

Best regards,
Shawn

>
>BR,
>Jani.
>
>
>>  		}
>>  	} else {
>>  		bd->props.power = FB_BLANK_POWERDOWN; diff --git 
>> a/drivers/gpu/drm/i915/display/intel_quirks.c 
>> b/drivers/gpu/drm/i915/display/intel_quirks.c
>> index 98dd787b00e3..ed57b083edbb 100644
>> --- a/drivers/gpu/drm/i915/display/intel_quirks.c
>> +++ b/drivers/gpu/drm/i915/display/intel_quirks.c
>> @@ -53,6 +53,12 @@ static void quirk_increase_ddi_disabled_time(struct drm_i915_private *i915)
>>  	drm_info(&i915->drm, "Applying Increase DDI Disabled quirk\n");  }
>>  
>> +static void quirk_keep_backlight_enable_on(struct drm_i915_private 
>> +*i915) {
>> +	i915->quirks |= QUIRK_KEEP_BACKLIGHT_ENABLE_ON;
>> +	drm_info(&i915->drm, "applying keep backlight enable on quirk\n"); }
>> +
>>  struct intel_quirk {
>>  	int device;
>>  	int subsystem_vendor;
>> @@ -72,6 +78,12 @@ static int intel_dmi_reverse_brightness(const struct dmi_system_id *id)
>>  	return 1;
>>  }
>>  
>> +static int backlight_wa_callback(const struct dmi_system_id *id) {
>> +	DRM_INFO("This is WA to ignore backlight off to prevent OLED panel issue on %s device\n", id->ident);
>> +	return 1;
>> +}
>> +
>>  static const struct intel_dmi_quirk intel_dmi_quirks[] = {
>>  	{
>>  		.dmi_id_list = &(const struct dmi_system_id[]) { @@ -96,6 +108,28 
>> @@ static const struct intel_dmi_quirk intel_dmi_quirks[] = {
>>  		},
>>  		.hook = quirk_invert_brightness,
>>  	},
>> +	{
>> +		.dmi_id_list = &(const struct dmi_system_id[]) {
>> +			{
>> +				.callback = backlight_wa_callback,
>> +				.ident = "Google Lillipup",
>> +				.matches = {DMI_MATCH(DMI_BOARD_VENDOR, "Google"),
>> +					    DMI_MATCH(DMI_BOARD_NAME, "Lindar"),
>> +					    DMI_MATCH(DMI_PRODUCT_SKU, "sku524294"),
>> +				},
>> +			},
>> +			{
>> +				.callback = backlight_wa_callback,
>> +				.ident = "Google Lillipup",
>> +				.matches = {DMI_MATCH(DMI_BOARD_VENDOR, "Google"),
>> +					    DMI_MATCH(DMI_BOARD_NAME, "Lindar"),
>> +					    DMI_MATCH(DMI_PRODUCT_SKU, "sku524295"),
>> +				},
>> +			},
>> +			{ }
>> +		},
>> +		.hook = quirk_keep_backlight_enable_on,
>> +	},
>>  };
>>  
>>  static struct intel_quirk intel_quirks[] = { diff --git 
>> a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h 
>> index 01e11fe38642..8103919bf3b4 100644
>> --- a/drivers/gpu/drm/i915/i915_drv.h
>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>> @@ -467,6 +467,7 @@ struct i915_drrs {  #define 
>> QUIRK_PIN_SWIZZLED_PAGES (1<<5)  #define QUIRK_INCREASE_T12_DELAY 
>> (1<<6)  #define QUIRK_INCREASE_DDI_DISABLED_TIME (1<<7)
>> +#define QUIRK_KEEP_BACKLIGHT_ENABLE_ON (1<<8)
>>  
>>  struct intel_fbdev;
>>  struct intel_fbc_work;
>
>--
>Jani Nikula, Intel Open Source Graphics Center
>
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