1 files changed, 19 insertions, 12 deletions

diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c
index 4b07401540ef..c275bf0fa36d 100644
--- a/drivers/gpu/drm/i915/intel_sdvo.c
+++ b/drivers/gpu/drm/i915/intel_sdvo.c
@@ -509,7 +509,7 @@ out:
 static bool intel_sdvo_read_response(struct intel_sdvo *intel_sdvo,
                                      void *response, int response_len)
 {
-        u8 retry = 5;
+        u8 retry = 15; /* 5 quick checks, followed by 10 long checks */
         u8 status;
         int i;
 
@@ -522,14 +522,27 @@ static bool intel_sdvo_read_response(struct intel_sdvo *intel_sdvo,
          * command to be complete.
          *
          * Check 5 times in case the hardware failed to read the docs.
+         *
+         * Also beware that the first response by many devices is to
+         * reply PENDING and stall for time. TVs are notorious for
+         * requiring longer than specified to complete their replies.
+         * Originally (in the DDX long ago), the delay was only ever 15ms
+         * with an additional delay of 30ms applied for TVs added later after
+         * many experiments. To accommodate both sets of delays, we do a
+         * sequence of slow checks if the device is falling behind and fails
+         * to reply within 5*15µs.
          */
         if (!intel_sdvo_read_byte(intel_sdvo,
                                   SDVO_I2C_CMD_STATUS,
                                   &status))
                 goto log_fail;
 
-        while (status == SDVO_CMD_STATUS_PENDING && retry--) {
-                udelay(15);
+        while (status == SDVO_CMD_STATUS_PENDING && --retry) {
+                if (retry < 10)
+                        msleep(15);
+                else
+                        udelay(15);
+
                 if (!intel_sdvo_read_byte(intel_sdvo,
                                           SDVO_I2C_CMD_STATUS,
                                           &status))
@@ -1535,15 +1548,9 @@ intel_sdvo_detect(struct drm_connector *connector, bool force)
         struct intel_sdvo_connector *intel_sdvo_connector = to_intel_sdvo_connector(connector);
         enum drm_connector_status ret;
 
-        if (!intel_sdvo_write_cmd(intel_sdvo,
-                                  SDVO_CMD_GET_ATTACHED_DISPLAYS, NULL, 0))
-                return connector_status_unknown;
-
-        /* add 30ms delay when the output type might be TV */
-        if (intel_sdvo->caps.output_flags & SDVO_TV_MASK)
-                msleep(30);
-
-        if (!intel_sdvo_read_response(intel_sdvo, &response, 2))
+        if (!intel_sdvo_get_value(intel_sdvo,
+                                  SDVO_CMD_GET_ATTACHED_DISPLAYS,
+                                  &response, 2))
                 return connector_status_unknown;
 
         DRM_DEBUG_KMS("SDVO response %d %d [%x]\n",