[PATCH 28/67] drm/amd/display: Prevent overflow on DTO calculation

[Zaeem Mohamed]

From: Chris Park <chris.park at amd.com>

[Why]
uint32_t is implicitly converted to uint64_t while multiplication
still happens on uint32_t side.  This creates digit overflow
for large pixel clock which is meant to be retained in uint64_t.

[How]
Calculate multiplication of units in uint64_t domain instead of
uint32_t in DTO parameter clock caculation.

Reviewed-by: Alvin Lee <alvin.lee2 at amd.com>
Acked-by: Zaeem Mohamed <zaeem.mohamed at amd.com>
Signed-off-by: Chris Park <chris.park at amd.com>
---
 .../gpu/drm/amd/display/dc/dce/dce_clock_source.c    | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 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 63deb5b60548..042a4187fff4 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
@@ -1088,11 +1088,15 @@ static bool dcn401_program_pix_clk(
 		dto_params.clk_src = DPREFCLK;
 
 		if (e) {
-			dto_params.pixclk_hz = e->target_pixel_rate_khz * e->mult_factor;
-			dto_params.refclk_hz = dtbclk_p_src_clk_khz * e->div_factor;
+			dto_params.pixclk_hz = e->target_pixel_rate_khz;
+			dto_params.pixclk_hz *= e->mult_factor;
+			dto_params.refclk_hz = dtbclk_p_src_clk_khz;
+			dto_params.refclk_hz *= e->div_factor;
 		} else {
-			dto_params.pixclk_hz = pix_clk_params->requested_pix_clk_100hz * 100;
-			dto_params.refclk_hz = dtbclk_p_src_clk_khz * 1000;
+			dto_params.pixclk_hz = pix_clk_params->requested_pix_clk_100hz;
+			dto_params.pixclk_hz *= 100;
+			dto_params.refclk_hz = dtbclk_p_src_clk_khz;
+			dto_params.refclk_hz *= 1000;
 		}
 
 		/* enable DP DTO */
-- 
2.34.1