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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Martin Leung <Martin.Leung@amd.com>,
        Qingqing Zhuo <qingqing.zhuo@amd.com>,
        David Galiffi <David.Galiffi@amd.com>,
        Daniel Wheeler <daniel.wheeler@amd.com>,
        Alex Deucher <alexander.deucher@amd.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.15 198/247] drm/amd/display: Check if modulo is 0 before dividing.
Date:   Mon, 13 Jun 2022 12:11:40 +0200
Message-Id: <20220613094928.954510878@linuxfoundation.org>
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From: David Galiffi <David.Galiffi@amd.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@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: David Galiffi <David.Galiffi@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.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 2c7eb982eabc..054823d12403 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
@@ -1013,9 +1013,12 @@ 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