drm/dp: Fix bogus DPCD version check in drm_dp_read_downstream_info()

Ville pointed this out to me when fixing some issues in drm_dp_read_downstream_info() - the DPCD version check here is bogus as there's no DisplayPort versions prior to 1.0. The original code from i915 that this was extracted from actually did: dpcd[DP_DPCD_REV] == DP_DPCD_REV_10 Which is correct, and somehow got missed when extracting this function. So let's fix this. Note that as far as I'm aware, I don't think this fixes any actual issues users are hitting. Signed-off-by: Lyude Paul <[email protected]> Cc: Ville Syrjälä <[email protected]> Reviewed-by: Ville Syrjälä <[email protected]> Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
blogic · May 10, 2021 · 208d8b9 · 208d8b9
1 parent 04dfe19
commit 208d8b9
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
@@ -677,7 +677,7 @@ int drm_dp_read_downstream_info(struct drm_dp_aux *aux,
 	memset(downstream_ports, 0, DP_MAX_DOWNSTREAM_PORTS);
 
 	/* No downstream info to read */
-	if (!drm_dp_is_branch(dpcd) || dpcd[DP_DPCD_REV] < DP_DPCD_REV_10)
+	if (!drm_dp_is_branch(dpcd) || dpcd[DP_DPCD_REV] == DP_DPCD_REV_10)
 		return 0;
 
 	/* Some branches advertise having 0 downstream ports, despite also advertising they have a