drm/amd/display: avoid 64-bit division (5f65ae34) · Commits · 戴 / test

On 32-bit architectures, dividing a 64-bit integer in the kernel leads to a link error: ERROR: "__udivdi3" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined! ERROR: "__divdi3" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined! Change the two recently introduced instances to a multiply+shift operation that is also much cheaper on 32-bit architectures. We can do that here, since both of them are really 32-bit numbers that change a few percent. Fixes: ("drm/amd/display: Move link functions from dc to dc_link") Fixes: ("drm/amd/display: update calculated bounding box logic for NV") Acked-by:

Slava Abramov <slava.abramov@amd.com> Tested-by:

Slava Abramov <slava.abramov@amd.com> Signed-off-by:

Arnd Bergmann <arnd@arndb.de> Signed-off-by:

Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_link.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -3072,8 +3072,8 @@ uint32_t dc_link_bandwidth_kbps(
		* but the difference is minimal and is in a safe direction,
		* which all works well around potential ambiguity of DP 1.4a spec.
		*/
		long long fec_link_bw_kbps = link_bw_kbps * 970LL;
		link_bw_kbps = (uint32_t)(fec_link_bw_kbps / 1000LL);
		link_bw_kbps = mul_u64_u32_shr(BIT_ULL(32) * 970LL / 1000,
		link_bw_kbps, 32);
		}
		#endif

drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -2647,7 +2647,7 @@ static void update_bounding_box(struct dc *dc, struct _vcs_dpi_soc_bounding_box_
		calculated_states[i].dram_speed_mts = uclk_states[i] * 16 / 1000;

		// FCLK:UCLK ratio is 1.08
		min_fclk_required_by_uclk = ((unsigned long long)uclk_states[i]) * 1080 / 1000000;
		min_fclk_required_by_uclk = mul_u64_u32_shr(BIT_ULL(32) * 1080 / 1000000, uclk_states[i], 32);

		calculated_states[i].fabricclk_mhz = (min_fclk_required_by_uclk < min_dcfclk) ?
		min_dcfclk : min_fclk_required_by_uclk;

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