linux-kernel - [PATCH AUTOSEL 5.18 45/68] drm/amd/display: Check if modulo is 0 before dividing.

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Message-Id: <20220607174846.477972-45-sashal@kernel.org>
Date:   Tue,  7 Jun 2022 13:48:11 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     David Galiffi <David.Galiffi@....com>,
        Martin Leung <Martin.Leung@....com>,
        Qingqing Zhuo <qingqing.zhuo@....com>,
        Daniel Wheeler <daniel.wheeler@....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@...ux.ie,
        daniel@...ll.ch, HaoPing.Liu@....com, Charlene.Liu@....com,
        Hansen.Dsouza@....com, Nevenko.Stupar@....com,
        dillon.varone@....com, alex.hung@....com, baihaowen@...zu.com,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 5.18 45/68] drm/amd/display: Check if modulo is 0 before dividing.

From: David Galiffi <David.Galiffi@....com>

[ Upstream commit 49947b906a6bd9668eaf4f9cf691973c25c26955 ]

[How & Why]
If a value of 0 is read, then this will cause a divide-by-0 panic.

Reviewed-by: Martin Leung <Martin.Leung@....com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@....com>
Signed-off-by: David Galiffi <David.Galiffi@....com>
Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c b/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c
index cc5128e67daf..8e9a7409c17a 100644
--- a/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c
+++ b/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c
@@ -1105,9 +1105,12 @@ static bool get_pixel_clk_frequency_100hz(
 			 * not be programmed equal to DPREFCLK
 			 */
 			modulo_hz = REG_READ(MODULO[inst]);
-			*pixel_clk_khz = div_u64((uint64_t)clock_hz*
-				clock_source->ctx->dc->clk_mgr->dprefclk_khz*10,
-				modulo_hz);
+			if (modulo_hz)
+				*pixel_clk_khz = div_u64((uint64_t)clock_hz*
+					clock_source->ctx->dc->clk_mgr->dprefclk_khz*10,
+					modulo_hz);
+			else
+				*pixel_clk_khz = 0;
 		} else {
 			/* NOTE: There is agreement with VBIOS here that MODULO is
 			 * programmed equal to DPREFCLK, in which case PHASE will be
-- 
2.35.1