Commit 1a794826 authored Oct 31, 2025 by Dan Carpenter Committed by Alex Deucher Nov 26, 2025

drm/amd/display: Fix logical vs bitwise bug in get_embedded_panel_info_v2_1()



The .H_SYNC_POLARITY and .V_SYNC_POLARITY variables are 1 bit bitfields
of a u32.  The ATOM_HSYNC_POLARITY define is 0x2 and the
ATOM_VSYNC_POLARITY is 0x4.  When we do a bitwise negate of 0, 2, or 4
then the last bit is always 1 so this code always sets .H_SYNC_POLARITY
and .V_SYNC_POLARITY to true.

This code is instead intended to check if the ATOM_HSYNC_POLARITY or
ATOM_VSYNC_POLARITY flags are set and reverse the result.  In other
words, it's supposed to be a logical negate instead of a bitwise negate.

Fixes: ae79c310 ("drm/amd/display: Add DCE12 bios parser support")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

parent 621e55f1

drivers/gpu/drm/amd/display/dc/bios/bios_parser2.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -1480,10 +1480,10 @@ static enum bp_result get_embedded_panel_info_v2_1(
		/* not provided by VBIOS */
		info->lcd_timing.misc_info.HORIZONTAL_CUT_OFF = 0;

		info->lcd_timing.misc_info.H_SYNC_POLARITY = ~(uint32_t) (lvds->lcd_timing.miscinfo
		& ATOM_HSYNC_POLARITY);
		info->lcd_timing.misc_info.V_SYNC_POLARITY = ~(uint32_t) (lvds->lcd_timing.miscinfo
		& ATOM_VSYNC_POLARITY);
		info->lcd_timing.misc_info.H_SYNC_POLARITY = !(lvds->lcd_timing.miscinfo &
		ATOM_HSYNC_POLARITY);
		info->lcd_timing.misc_info.V_SYNC_POLARITY = !(lvds->lcd_timing.miscinfo &
		ATOM_VSYNC_POLARITY);

		/* not provided by VBIOS */
		info->lcd_timing.misc_info.VERTICAL_CUT_OFF = 0;