[PATCH 1/2] drm/display/dp: Check for MSTM_CAP before MSTM_CTRL write
Lin, Charlton
charlton.lin at intel.com
Tue Jan 30 07:56:26 UTC 2024
On 1/27/2024 12:06 PM, Arun R Murthy wrote:
> With DP2.1, multistream packetization and the underneth MST protocol
> will be required for SST. So check for MSTM_CAP to see if MST is really
> required and skip the MSTM_CTRL write so that we ensure that only the
> underneth protocol and the multistream packetization will be enabled and
> sink will not be confused by a corresponding dpcd write.
>
> Signed-off-by: Arun R Murthy <arun.r.murthy at intel.com>
> ---
> drivers/gpu/drm/display/drm_dp_mst_topology.c | 26 +++++++++++--------
> 1 file changed, 15 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> index 8ca01a6bf645..22d81732a978 100644
> --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> @@ -3666,10 +3666,11 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms
> mgr->mst_primary = mstb;
> drm_dp_mst_topology_get_mstb(mgr->mst_primary);
>
> - ret = drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL,
> - DP_MST_EN |
> - DP_UP_REQ_EN |
> - DP_UPSTREAM_IS_SRC);
> + if (drm_dp_read_mst_cap(mgr->aux, mgr->dpcd))
> + ret = drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL,
> + DP_MST_EN |
> + DP_UP_REQ_EN |
> + DP_UPSTREAM_IS_SRC);
> if (ret < 0)
> goto out_unlock;
>
> @@ -3684,7 +3685,8 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms
> mstb = mgr->mst_primary;
> mgr->mst_primary = NULL;
> /* this can fail if the device is gone */
> - drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL, 0);
> + if (drm_dp_read_mst_cap(mgr->aux, mgr->dpcd))
> + drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL, 0);
> ret = 0;
> mgr->payload_id_table_cleared = false;
>
> @@ -3724,8 +3726,9 @@ drm_dp_mst_topology_mgr_invalidate_mstb(struct drm_dp_mst_branch *mstb)
> void drm_dp_mst_topology_mgr_suspend(struct drm_dp_mst_topology_mgr *mgr)
> {
> mutex_lock(&mgr->lock);
> - drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL,
> - DP_MST_EN | DP_UPSTREAM_IS_SRC);
> + if (drm_dp_read_mst_cap(mgr->aux, mgr->dpcd))
> + drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL,
> + DP_MST_EN | DP_UPSTREAM_IS_SRC);
> mutex_unlock(&mgr->lock);
> flush_work(&mgr->up_req_work);
> flush_work(&mgr->work);
> @@ -3773,10 +3776,11 @@ int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr,
> goto out_fail;
> }
>
> - ret = drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL,
> - DP_MST_EN |
> - DP_UP_REQ_EN |
> - DP_UPSTREAM_IS_SRC);
> + if (drm_dp_read_mst_cap(mgr->aux, mgr->dpcd))
> + ret = drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL,
This did not compile in Chrome dev environemnt due to uninitialized variable ret.
> + DP_MST_EN |
> + DP_UP_REQ_EN |
> + DP_UPSTREAM_IS_SRC);
> if (ret < 0) {
> drm_dbg_kms(mgr->dev, "mst write failed - undocked during suspend?\n");
> goto out_fail;
Tested-by: Charlton Lin <charlton.lin at intel.com>
Regards,
Charlton Lin
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