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Subject[PATCH 4/6] drm/i915: Skip vcpi allocation for MSTB ports that are gone
Date
Since we need to be able to allow DPMS on->off prop changes after an MST
port has disappeared from the system, we need to be able to make sure we
can compute a config for the resulting atomic commit. Currently this is
impossible when the port has disappeared, since the VCPI slot searching
we try to do in intel_dp_mst_compute_config() will fail with -EINVAL.

Since the only commits we want to allow on no-longer-present MST ports
are ones that shut off display hardware, we already know that no VCPI
allocations are needed. So, hardcode the VCPI slot count to 0 when
intel_dp_mst_compute_config() is called on an MST port that's gone.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: stable@vger.kernel.org
---
drivers/gpu/drm/i915/intel_dp_mst.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
index fcb9b87b9339..a366f32b048a 100644
--- a/drivers/gpu/drm/i915/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/intel_dp_mst.c
@@ -42,7 +42,7 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
to_intel_connector(conn_state->connector);
struct drm_atomic_state *state = pipe_config->base.state;
int bpp;
- int lane_count, slots;
+ int lane_count, slots = 0;
const struct drm_display_mode *adjusted_mode = &pipe_config->base.adjusted_mode;
int mst_pbn;
bool reduce_m_n = drm_dp_has_quirk(&intel_dp->desc,
@@ -76,11 +76,16 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
mst_pbn = drm_dp_calc_pbn_mode(adjusted_mode->crtc_clock, bpp);
pipe_config->pbn = mst_pbn;

- slots = drm_dp_atomic_find_vcpi_slots(state, &intel_dp->mst_mgr,
- connector->port, mst_pbn);
- if (slots < 0) {
- DRM_DEBUG_KMS("failed finding vcpi slots:%d\n", slots);
- return false;
+ if (!connector->mst_port_gone) {
+ slots = drm_dp_atomic_find_vcpi_slots(state,
+ &intel_dp->mst_mgr,
+ connector->port,
+ mst_pbn);
+ if (slots < 0) {
+ DRM_DEBUG_KMS("failed finding vcpi slots:%d\n",
+ slots);
+ return false;
+ }
}

intel_link_compute_m_n(bpp, lane_count,
--
2.17.1
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