From: Lyude Paul Date: Fri, 7 May 2021 21:42:09 +0000 (-0400) Subject: drm/dp: Fix bogus DPCD version check in drm_dp_read_downstream_info() X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=208d8b9d26f5fd0f7c0fcaa460873bbd6b5bebfa;p=linux.git 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 Cc: Ville Syrjälä Reviewed-by: Ville Syrjälä Link: https://patchwork.freedesktop.org/patch/msgid/20210507214209.554866-1-lyude@redhat.com --- diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 0f84df8798ab9..55b53df6ce348 100644 --- 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