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From 27fea314a44d74be59af60aecc13eb9bc6b66fcd Mon Sep 17 00:00:00 2001
From: Yongqiang Sun <yongqiang.sun@amd.com>
Date: Wed, 7 Mar 2018 09:12:53 -0500
Subject: [PATCH 3920/4131] drm/amd/display: Retry when read dpcd caps failed.
Some DP panel not detected intermittently due to read dpcd
caps failed when doing hot plug.
[root cause] DC_HPD_CONNECT_INT_DELAY is set to 0, not delay
after HPD toggle and read dpcd data, while some panel need 4ms defer
to read.
[solution] Add a retry when read failed.
Signed-off-by: Yongqiang Sun <yongqiang.sun@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
---
drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
index 3b50535..b86325b 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
@@ -2278,6 +2278,8 @@ static bool retrieve_link_cap(struct dc_link *link)
union edp_configuration_cap edp_config_cap;
union dp_downstream_port_present ds_port = { 0 };
enum dc_status status = DC_ERROR_UNEXPECTED;
+ uint32_t read_dpcd_retry_cnt = 3;
+ int i;
memset(dpcd_data, '\0', sizeof(dpcd_data));
memset(&down_strm_port_count,
@@ -2285,11 +2287,15 @@ static bool retrieve_link_cap(struct dc_link *link)
memset(&edp_config_cap, '\0',
sizeof(union edp_configuration_cap));
- status = core_link_read_dpcd(
- link,
- DP_DPCD_REV,
- dpcd_data,
- sizeof(dpcd_data));
+ for (i = 0; i < read_dpcd_retry_cnt; i++) {
+ status = core_link_read_dpcd(
+ link,
+ DP_DPCD_REV,
+ dpcd_data,
+ sizeof(dpcd_data));
+ if (status == DC_OK)
+ break;
+ }
if (status != DC_OK) {
dm_error("%s: Read dpcd data failed.\n", __func__);
--
2.7.4
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