Commit b231933d authored by Iswara Nagulendran's avatar Iswara Nagulendran Committed by Alex Deucher
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drm/amd/display: Read before writing Backlight Mode Set Register 



[HOW&WHY]
Reading the value from
DP_EDP_BACKLIGHT_MODE_SET_REGISTER, DPCD 0x721
before setting the
BP_EDP_PANEL_LUMINANC_CONTROL_ENABLE bit
to ensure there are no accidental overwrites.

Reviewed-by: default avatarSreeja Golui <sreeja.golui@amd.com>
Reviewed-by: default avatarHarry Vanzylldejong <harry.vanzylldejong@amd.com>
Acked-by: default avatarRoman Li <roman.li@amd.com>
Signed-off-by: default avatarIswara Nagulendran <iswara.nagulendran@amd.com>
Tested-by: default avatarDaniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent 1b9ec7cb

drivers/gpu/drm/amd/display/dc/link/protocols/link_edp_panel_control.c

+6 −1
Original line number Diff line number Diff line
@@ -182,7 +182,7 @@ bool edp_set_backlight_level_nits(struct dc_link *link, 
			&backlight_control, 1) != DC_OK)

			return false;

	} else {

		const uint8_t backlight_enable = DP_EDP_PANEL_LUMINANCE_CONTROL_ENABLE;

		uint8_t backlight_enable = 0;

		struct target_luminance_value *target_luminance = NULL;



		//if target luminance value is greater than 24 bits, clip the value to 24 bits
@@ -191,6 +191,11 @@ bool edp_set_backlight_level_nits(struct dc_link *link, 


		target_luminance = (struct target_luminance_value *)&backlight_millinits;



		core_link_read_dpcd(link, DP_EDP_BACKLIGHT_MODE_SET_REGISTER,

			&backlight_enable, sizeof(uint8_t));



		backlight_enable |= DP_EDP_PANEL_LUMINANCE_CONTROL_ENABLE;



		if (core_link_write_dpcd(link, DP_EDP_BACKLIGHT_MODE_SET_REGISTER,

			&backlight_enable,

			sizeof(backlight_enable)) != DC_OK)