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drm/rockchip: cdn-dp: fix sign extension on an int multiply for a u64 result

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The variable bit_per_pix is a u8 and is promoted in the multiplication
to an int type and then sign extended to a u64. If the result of the
int multiplication is greater than 0x7fffffff then the upper 32 bits will
be set to 1 as a result of the sign extension. Avoid this by casting
tu_size_reg to u64 to avoid sign extension and also a potential overflow.

Fixes: 1a0f7ed3ab ("drm/rockchip: cdn-dp: add cdn DP support for rk3399")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20200915162049.36434-1-colin.king@canonical.com
This commit is contained in:
Colin Ian King 2020-09-15 17:20:49 +01:00 committed by Heiko Stuebner
parent 3dfa159f6b
commit ce0cb93a5a
1 changed files with 1 additions and 1 deletions
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2
drivers/gpu/drm/rockchip/cdn-dp-reg.c
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@ -658,7 +658,7 @@ int cdn_dp_config_video(struct cdn_dp_device *dp)
*/
do {
tu_size_reg += 2;
symbol = tu_size_reg * mode->clock * bit_per_pix;
symbol = (u64)tu_size_reg * mode->clock * bit_per_pix;
do_div(symbol, dp->max_lanes * link_rate * 8);
rem = do_div(symbol, 1000);
if (tu_size_reg > 64) {