drm/amd/display: Passive DP->HDMI dongle detection fix

[WHY]
i2c_read is called to differentiate passive DP->HDMI and DP->DVI-D dongles
The call is expected to fail in DVI-D case but pass in HDMI case
Some HDMI dongles have a chance to fail as well, causing misdetection as DVI-D

[HOW]
Retry i2c_read to ensure failed result is valid

Signed-off-by: Michael Strauss <michael.strauss@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_ddc.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_ddc.c
index 505967b48e144b7701dc0c70f92299636c6965ad..51991bf26a93cb9ee1484d5a45856331d242c2c4 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_ddc.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_ddc.c
@@ -374,6 +374,7 @@ void dal_ddc_service_i2c_query_dp_dual_mode_adaptor(
        enum display_dongle_type *dongle = &sink_cap->dongle_type;
        uint8_t type2_dongle_buf[DP_ADAPTOR_TYPE2_SIZE];
        bool is_type2_dongle = false;
+       int retry_count = 2;
        struct dp_hdmi_dongle_signature_data *dongle_signature;
 
        /* Assume we have no valid DP passive dongle connected */
@@ -386,13 +387,24 @@ void dal_ddc_service_i2c_query_dp_dual_mode_adaptor(
                DP_HDMI_DONGLE_ADDRESS,
                type2_dongle_buf,
                sizeof(type2_dongle_buf))) {
-               *dongle = DISPLAY_DONGLE_DP_DVI_DONGLE;
-               sink_cap->max_hdmi_pixel_clock = DP_ADAPTOR_DVI_MAX_TMDS_CLK;
+               /* Passive HDMI dongles can sometimes fail here without retrying*/
+               while (retry_count > 0) {
+                       if (i2c_read(ddc,
+                               DP_HDMI_DONGLE_ADDRESS,
+                               type2_dongle_buf,
+                               sizeof(type2_dongle_buf)))
+                               break;
+                       retry_count--;
+               }
+               if (retry_count == 0) {
+                       *dongle = DISPLAY_DONGLE_DP_DVI_DONGLE;
+                       sink_cap->max_hdmi_pixel_clock = DP_ADAPTOR_DVI_MAX_TMDS_CLK;
 
-               CONN_DATA_DETECT(ddc->link, type2_dongle_buf, sizeof(type2_dongle_buf),
-                               "DP-DVI passive dongle %dMhz: ",
-                               DP_ADAPTOR_DVI_MAX_TMDS_CLK / 1000);
-               return;
+                       CONN_DATA_DETECT(ddc->link, type2_dongle_buf, sizeof(type2_dongle_buf),
+                                       "DP-DVI passive dongle %dMhz: ",
+                                       DP_ADAPTOR_DVI_MAX_TMDS_CLK / 1000);
+                       return;
+               }
        }
 
        /* Check if Type 2 dongle.*/