From: Rodrigo Siqueira Rodrigo.Siqueira@amd.com
[ Upstream commit ca08a1725d0d78efca8d2dbdbce5ea70355da0f2 ]
When using a device based on DCN32/321, we have an issue where a second 4k@60Hz display does not light up, and the system becomes unresponsive for a few minutes. In the debug process, it was possible to see a hang in the function dcn20_post_unlock_program_front_end in this part:
for (j = 0; j < TIMEOUT_FOR_PIPE_ENABLE_MS*1000 && hubp->funcs->hubp_is_flip_pending(hubp); j++) mdelay(1); }
The hubp_is_flip_pending always returns positive for waiting pending flips which is a symptom of pipe hang. Additionally, the dmesg log shows this message after a few minutes:
BUG: soft lockup - CPU#4 stuck for 26s! ... [ +0.000003] dcn20_post_unlock_program_front_end+0x112/0x340 [amdgpu] [ +0.000171] dc_commit_state_no_check+0x63d/0xbf0 [amdgpu] [ +0.000155] ? dc_validate_global_state+0x358/0x3d0 [amdgpu] [ +0.000154] dc_commit_state+0xe2/0xf0 [amdgpu]
This confirmed the hypothesis that we had a pipe hanging somewhere. Next, after checking the ftrace entries, we have the below weird sequence:
[..] 2) | dcn10_lock_all_pipes [amdgpu]() { 2) 0.120 us | optc1_is_tg_enabled [amdgpu](); 2) | dcn20_pipe_control_lock [amdgpu]() { 2) | dc_dmub_srv_clear_inbox0_ack [amdgpu]() { 2) 0.121 us | amdgpu_dm_dmub_reg_write [amdgpu](); 2) 0.551 us | } 2) | dc_dmub_srv_send_inbox0_cmd [amdgpu]() { 2) 0.110 us | amdgpu_dm_dmub_reg_write [amdgpu](); 2) 0.511 us | } 2) | dc_dmub_srv_wait_for_inbox0_ack [amdgpu]() { 2) 0.110 us | amdgpu_dm_dmub_reg_read [amdgpu](); 2) 0.110 us | amdgpu_dm_dmub_reg_read [amdgpu](); 2) 0.110 us | amdgpu_dm_dmub_reg_read [amdgpu](); 2) 0.110 us | amdgpu_dm_dmub_reg_read [amdgpu](); 2) 0.110 us | amdgpu_dm_dmub_reg_read [amdgpu](); 2) 0.110 us | amdgpu_dm_dmub_reg_read [amdgpu](); 2) 0.110 us | amdgpu_dm_dmub_reg_read [amdgpu](); [..]
We are not expected to read from dmub register so many times and for so long. From the trace log, it was possible to identify that the function dcn20_pipe_control_lock was triggering the dmub operation when it was unnecessary and causing the hang issue. This commit drops the unnecessary dmub code and, consequently, fixes the second display not lighting up the issue.
Tested-by: Daniel Wheeler daniel.wheeler@amd.com Acked-by: Qingqing Zhuo qingqing.zhuo@amd.com Signed-off-by: Rodrigo Siqueira Rodrigo.Siqueira@amd.com Signed-off-by: Alex Deucher alexander.deucher@amd.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c index 8f66eef0c683..c6c4888c6665 100644 --- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c +++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c @@ -1746,7 +1746,7 @@ void dcn20_post_unlock_program_front_end(
for (j = 0; j < TIMEOUT_FOR_PIPE_ENABLE_MS*1000 && hubp->funcs->hubp_is_flip_pending(hubp); j++) - mdelay(1); + udelay(1); } }