[PATCH 1/4] drm/amd/display: Wait until OTG enable state is cleared

[Tom Chung]

From: TungYu Lu <tungyu...@amd.com>

[Why]
Customer reported an issue that OS starts and stops device multiple times
during driver installation. Frequently disabling and enabling OTG may
prevent OTG from being safely disabled and cause incorrect configuration
upon the next enablement.

[How]
Add a wait until OTG_CURRENT_MASTER_EN_STATE is cleared as a short term
solution.

Reviewed-by: Dillon Varone <dillon.var...@amd.com>
Signed-off-by: TungYu Lu <tungyu...@amd.com>
Signed-off-by: Tom Chung <chiahsuan.ch...@amd.com>
---
 drivers/gpu/drm/amd/display/dc/optc/dcn401/dcn401_optc.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/optc/dcn401/dcn401_optc.c 
b/drivers/gpu/drm/amd/display/dc/optc/dcn401/dcn401_optc.c
index ff79c38287df..5af13706e601 100644
--- a/drivers/gpu/drm/amd/display/dc/optc/dcn401/dcn401_optc.c
+++ b/drivers/gpu/drm/amd/display/dc/optc/dcn401/dcn401_optc.c
@@ -226,6 +226,11 @@ bool optc401_disable_crtc(struct timing_generator *optc)
        REG_UPDATE(CONTROL,
                        VTG0_ENABLE, 0);
 
+       // wait until CRTC_CURRENT_MASTER_EN_STATE == 0
+       REG_WAIT(OTG_CONTROL,
+                        OTG_CURRENT_MASTER_EN_STATE,
+                        0, 10, 15000);
+
        /* CRTC disabled, so disable  clock. */
        REG_WAIT(OTG_CLOCK_CONTROL,
                        OTG_BUSY, 0,
-- 
2.43.0