linux-kernel - [PATCH AUTOSEL 6.6 38/47] drm/amd/display: Use channel

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Date:   Mon, 11 Dec 2023 08:50:39 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Alvin Lee <alvin.lee2@....com>,
        Daniel Wheeler <daniel.wheeler@....com>,
        Samson Tam <samson.tam@....com>,
        Rodrigo Siqueira <rodrigo.siqueira@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>, harry.wentland@....com,
        sunpeng.li@....com, Rodrigo.Siqueira@....com,
        christian.koenig@....com, Xinhui.Pan@....com, airlied@...il.com,
        daniel@...ll.ch, tony.tascioglu@....com, felipe.clark@....com,
        drv@...lo.com, ruanjinjie@...wei.com, sunran001@...suo.com,
        mario.limonciello@....com, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 6.6 38/47] drm/amd/display: Use channel_width = 2 for vram table 3.0

From: Alvin Lee <alvin.lee2@....com>

[ Upstream commit fec05adc40c25a028c9dfa9d540f800a2d433f80 ]

VBIOS has suggested to use channel_width=2 for any ASIC that uses vram
info 3.0. This is because channel_width in the vram table no longer
represents the memory width

Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Reviewed-by: Samson Tam <samson.tam@....com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@....com>
Signed-off-by: Alvin Lee <alvin.lee2@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/display/dc/bios/bios_parser2.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/bios/bios_parser2.c b/drivers/gpu/drm/amd/display/dc/bios/bios_parser2.c
index 484d62bcf2c2e..c523561471484 100644
--- a/drivers/gpu/drm/amd/display/dc/bios/bios_parser2.c
+++ b/drivers/gpu/drm/amd/display/dc/bios/bios_parser2.c
@@ -2398,7 +2398,13 @@ static enum bp_result get_vram_info_v30(
 		return BP_RESULT_BADBIOSTABLE;
 
 	info->num_chans = info_v30->channel_num;
-	info->dram_channel_width_bytes = (1 << info_v30->channel_width) / 8;
+	/* As suggested by VBIOS we should always use
+	 * dram_channel_width_bytes = 2 when using VRAM
+	 * table version 3.0. This is because the channel_width
+	 * param in the VRAM info table is changed in 7000 series and
+	 * no longer represents the memory channel width.
+	 */
+	info->dram_channel_width_bytes = 2;
 
 	return result;
 }
-- 
2.42.0