While the DP specification isn't entirely clear on if this should be allowed or not, some branch devices report having downstream ports present while also reporting a downstream port count of 0. So to avoid breaking those devices, we need to handle this in drm_dp_read_downstream_info().
So, to do this we assume there's no downstream port info when the downstream port count is 0.
Signed-off-by: Lyude Paul lyude@redhat.com Tested-by: Jérôme de Bretagne jerome.debretagne@gmail.com Bugzilla: https://gitlab.freedesktop.org/drm/intel/-/issues/3416 Fixes: 3d3721ccb18a ("drm/i915/dp: Extract drm_dp_read_downstream_info()") Cc: stable@vger.kernel.org # v5.10+ --- drivers/gpu/drm/drm_dp_helper.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index cb56d74e9d38..27c8c5bdf7d9 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -682,7 +682,14 @@ int drm_dp_read_downstream_info(struct drm_dp_aux *aux, !(dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT)) return 0;
+ /* Some branches advertise having 0 downstream ports, despite also advertising they have a + * downstream port present. The DP spec isn't clear on if this is allowed or not, but since + * some branches do it we need to handle it regardless. + */ len = drm_dp_downstream_port_count(dpcd); + if (!len) + return 0; + if (dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DETAILED_CAP_INFO_AVAILABLE) len *= 4;
Noticed this while fixing another issue in drm_dp_read_downstream_info(), the open coded DP_DOWNSTREAMPORT_PRESENT check here just duplicates what we already do in drm_dp_is_branch(), so just get rid of it.
Signed-off-by: Lyude Paul lyude@redhat.com --- drivers/gpu/drm/drm_dp_helper.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 27c8c5bdf7d9..0f84df8798ab 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -677,9 +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 || - !(dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT)) + 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
On Fri, Apr 30, 2021 at 06:34:28PM -0400, Lyude Paul wrote:
Noticed this while fixing another issue in drm_dp_read_downstream_info(), the open coded DP_DOWNSTREAMPORT_PRESENT check here just duplicates what we already do in drm_dp_is_branch(), so just get rid of it.
Signed-off-by: Lyude Paul lyude@redhat.com
drivers/gpu/drm/drm_dp_helper.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 27c8c5bdf7d9..0f84df8798ab 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -677,9 +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 ||!(dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT))
- if (!drm_dp_is_branch(dpcd) || dpcd[DP_DPCD_REV] < DP_DPCD_REV_10)
BTW that DPCD_REV check looks rather wrong.
Reviewed-by: Ville Syrjälä ville.syrjala@linux.intel.com
return 0;/* Some branches advertise having 0 downstream ports, despite also advertising they have a
2.30.2
Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
On Mon, 2021-05-03 at 06:06 +0300, Ville Syrjälä wrote:
On Fri, Apr 30, 2021 at 06:34:28PM -0400, Lyude Paul wrote:
Noticed this while fixing another issue in drm_dp_read_downstream_info(), the open coded DP_DOWNSTREAMPORT_PRESENT check here just duplicates what we already do in drm_dp_is_branch(), so just get rid of it.
Signed-off-by: Lyude Paul lyude@redhat.com
drivers/gpu/drm/drm_dp_helper.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 27c8c5bdf7d9..0f84df8798ab 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -677,9 +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 || - !(dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT)) + if (!drm_dp_is_branch(dpcd) || dpcd[DP_DPCD_REV] < DP_DPCD_REV_10)
BTW that DPCD_REV check looks rather wrong.
Reviewed-by: Ville Syrjälä ville.syrjala@linux.intel.com
I'll send out a separate fix for this in just a moment, thanks for pointing it out!
return 0; /* Some branches advertise having 0 downstream ports, despite also advertising they have a -- 2.30.2
Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
On Fri, Apr 30, 2021 at 06:34:27PM -0400, Lyude Paul wrote:
While the DP specification isn't entirely clear on if this should be allowed or not, some branch devices report having downstream ports present while also reporting a downstream port count of 0. So to avoid breaking those devices, we need to handle this in drm_dp_read_downstream_info().
So, to do this we assume there's no downstream port info when the downstream port count is 0.
Signed-off-by: Lyude Paul lyude@redhat.com Tested-by: Jérôme de Bretagne jerome.debretagne@gmail.com Bugzilla: https://gitlab.freedesktop.org/drm/intel/-/issues/3416 Fixes: 3d3721ccb18a ("drm/i915/dp: Extract drm_dp_read_downstream_info()") Cc: stable@vger.kernel.org # v5.10+
drivers/gpu/drm/drm_dp_helper.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index cb56d74e9d38..27c8c5bdf7d9 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -682,7 +682,14 @@ int drm_dp_read_downstream_info(struct drm_dp_aux *aux, !(dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT)) return 0;
- /* Some branches advertise having 0 downstream ports, despite also advertising they have a
* downstream port present. The DP spec isn't clear on if this is allowed or not, but since* some branches do it we need to handle it regardless.*/- if (!len)
return 0;
Seems sane enough.
Reviewed-by: Ville Syrjälä ville.syrjala@linux.intel.com
if (dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DETAILED_CAP_INFO_AVAILABLE) len *= 4;
-- 2.30.2
dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
dri-devel@lists.freedesktop.org
-
Lyude Paul -
Ville Syrjälä