Commit ce0cb93a authored by Colin Ian King's avatar Colin Ian King Committed by Heiko Stuebner
Browse files

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



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: 1a0f7ed3 ("drm/rockchip: cdn-dp: add cdn DP support for rk3399")
Signed-off-by: default avatarColin Ian King <colin.king@canonical.com>
Reviewed-by: default avatarGuenter Roeck <groeck@chromium.org>
Signed-off-by: default avatarHeiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20200915162049.36434-1-colin.king@canonical.com
parent 3dfa159f

drivers/gpu/drm/rockchip/cdn-dp-reg.c

+1 −1
Original line number Diff line number Diff line
@@ -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) {