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Rodrigo Siqueira 004decd41b drm/amd/display: Remove wrong pipe control lock 
[ Upstream commit ca08a1725d ]

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>
History 2022-11-26 09:24:30 +01:00
arch x86/cpu: Restore AMD's DE_CFG MSR after resume 2022-11-16 09:58:31 +01:00
block block, bfq: protect 'bfqd->queued' by 'bfqd->lock' 2022-11-10 18:15:37 +01:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: akcipher - default implementation for setting a private key 2022-10-26 12:35:25 +02:00
Documentation KVM: s390: pv: don't allow userspace to set the clock under PV 2022-11-16 09:58:17 +01:00
drivers drm/amd/display: Remove wrong pipe control lock 2022-11-26 09:24:30 +01:00
fs udf: Fix a slab-out-of-bounds write bug in udf_find_entry() 2022-11-16 09:58:27 +01:00
include marvell: octeontx2: build error: unknown type name 'u64' 2022-11-16 09:58:30 +01:00
init stack: Declare {randomize_,}kstack_offset to fix Sparse warnings 2022-08-17 14:23:10 +02:00
ipc ipc/mqueue: use get_tree_nodev() in mqueue_get_tree() 2022-06-09 10:23:10 +02:00
kernel bpf: Fix wrong reg type conversion in release_reference() 2022-11-16 09:58:15 +01:00
lib lib/Kconfig.debug: Add check for non-constant .{s,u}leb128 support to DWARF5 2022-10-26 12:35:55 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm: shmem: don't truncate page if memory failure happens 2022-11-26 09:24:28 +01:00
net can: j1939: j1939_send_one(): fix missing CAN header initialization 2022-11-16 09:58:28 +01:00
samples samples/landlock: Format with clang-format 2022-06-09 10:23:23 +02:00
scripts cert host tools: Stop complaining about deprecated OpenSSL functions 2022-11-16 09:58:28 +01:00
security capabilities: fix potential memleak on error path from vfs_getxattr_alloc() 2022-11-10 18:15:39 +01:00
sound ASoC: rt1308-sdw: add the default value of some registers 2022-11-26 09:24:30 +01:00
tools selftests/intel_pstate: fix build for ARCH=x86_64 2022-11-26 09:24:30 +01:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt kvm: Add support for arch compat vm ioctls 2022-10-29 10:12:54 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Input: goodix - add a goodix.h header file 2022-07-12 16:34:51 +02:00
Makefile Linux 5.15.79 2022-11-16 09:58:31 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.