drm/i915: Add 30ms delay to make SDVO TV detection reliable.

Without this, on some boots the TV wouldn't be detected.  Testing
showed 15ms to be insufficient.

https://bugs.freedesktop.org/show_bug.cgi?id=24290
https://bugs.freedesktop.org/show_bug.cgi?id=20785

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Tested-by: Yan Seiner <yan@seiner.com>
Signed-off-by: Eric Anholt <eric@anholt.net>

diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c
index 55b8beb..dba5147 100644 (file)
--- a/drivers/gpu/drm/i915/intel_sdvo.c
+++ b/drivers/gpu/drm/i915/intel_sdvo.c
@@ -1617,6 +1617,10 @@ static enum drm_connector_status intel_sdvo_detect(struct drm_connector *connect
 
        intel_sdvo_write_cmd(intel_output,
                             SDVO_CMD_GET_ATTACHED_DISPLAYS, NULL, 0);
+       if (sdvo_priv->is_tv) {
+               /* add 30ms delay when the output type is SDVO-TV */
+               mdelay(30);
+       }
        status = intel_sdvo_read_response(intel_output, &response, 2);
 
        DRM_DEBUG_KMS("SDVO response %d %d\n", response & 0xff, response >> 8);