linux-kernel - [PATCH 3/3] drm/amdgpu/display: fix integer arithmetic problem

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Date:   Thu,  2 Nov 2017 12:26:43 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>
Cc:     Arnd Bergmann <arnd@...db.de>, David Airlie <airlied@...ux.ie>,
        Harry Wentland <harry.wentland@....com>,
        Tony Cheng <tony.cheng@....com>,
        Dmytro Laktyushkin <Dmytro.Laktyushkin@....com>,
        Joshua Aberback <Joshua.Aberback@....com>,
        "Leo (Sunpeng) Li" <sunpeng.li@....com>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] drm/amdgpu/display: fix integer arithmetic problem

gcc warns about an ambiguous integer calculation:

drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dce_calcs.c: In function 'calculate_bandwidth':
drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dce_calcs.c:534:5: error: this decimal constant is unsigned only in ISO C90 [-Werror]
     data->lb_line_pitch = bw_ceil2(bw_mul(bw_div(bw_frc_to_fixed(2401171875, 100000000), bw_int_to_fixed(3)), bw_ceil2(data->source_width_in_lb, bw_int_to_fixed(8))), bw_int_to_fixed(48));
     ^~~~

Marking the constant as explicitly unsigned makes it work fine everywhere
without warnings.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c b/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c
index 15cbfc400633..4f8a95368ffc 100644
--- a/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c
+++ b/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c
@@ -531,7 +531,7 @@ static void calculate_bandwidth(
 			}
 			switch (data->lb_bpc[i]) {
 			case 8:
-				data->lb_line_pitch = bw_ceil2(bw_mul(bw_div(bw_frc_to_fixed(2401171875, 100000000), bw_int_to_fixed(3)), bw_ceil2(data->source_width_in_lb, bw_int_to_fixed(8))), bw_int_to_fixed(48));
+				data->lb_line_pitch = bw_ceil2(bw_mul(bw_div(bw_frc_to_fixed(2401171875ul, 100000000), bw_int_to_fixed(3)), bw_ceil2(data->source_width_in_lb, bw_int_to_fixed(8))), bw_int_to_fixed(48));
 				break;
 			case 10:
 				data->lb_line_pitch = bw_ceil2(bw_mul(bw_div(bw_frc_to_fixed(300234375, 10000000), bw_int_to_fixed(3)), bw_ceil2(data->source_width_in_lb, bw_int_to_fixed(8))), bw_int_to_fixed(48));
-- 
2.9.0