Alright, managed to figure out my MST woes! Just tested with nouveau and I see no regressions :) Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx> On Fri, 2023-06-09 at 18:49 +0800, Wayne Lin wrote: > [Why] > The sequence for collecting down_reply from source perspective should > be: > > Request_n->repeat (get partial reply of Request_n->clear message ready > flag to ack DPRX that the message is received) till all partial > replies for Request_n are received->new Request_n+1. > > Now there is chance that drm_dp_mst_hpd_irq() will fire new down > request in the tx queue when the down reply is incomplete. Source is > restricted to generate interveleaved message transactions so we should > avoid it. > > Also, while assembling partial reply packets, reading out DPCD DOWN_REP > Sideband MSG buffer + clearing DOWN_REP_MSG_RDY flag should be > wrapped up as a complete operation for reading out a reply packet. > Kicking off a new request before clearing DOWN_REP_MSG_RDY flag might > be risky. e.g. If the reply of the new request has overwritten the > DPRX DOWN_REP Sideband MSG buffer before source writing one to clear > DOWN_REP_MSG_RDY flag, source then unintentionally flushes the reply > for the new request. Should handle the up request in the same way. > > [How] > Separete drm_dp_mst_hpd_irq() into 2 steps. After acking the MST IRQ > event, driver calls drm_dp_mst_hpd_irq_send_new_request() and might > trigger drm_dp_mst_kick_tx() only when there is no on going message > transaction. > > Changes since v1: > * Reworked on review comments received > -> Adjust the fix to let driver explicitly kick off new down request > when mst irq event is handled and acked > -> Adjust the commit message > > Changes since v2: > * Adjust the commit message > * Adjust the naming of the divided 2 functions and add a new input > parameter "ack". > * Adjust code flow as per review comments. > > Changes since v3: > * Update the function description of drm_dp_mst_hpd_irq_handle_event > > Changes since v4: > * Change ack of drm_dp_mst_hpd_irq_handle_event() to be an array align > the size of esi[] > > Signed-off-by: Wayne Lin <Wayne.Lin@xxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx > --- > .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 32 +++++------ > drivers/gpu/drm/display/drm_dp_mst_topology.c | 54 ++++++++++++++++--- > drivers/gpu/drm/i915/display/intel_dp.c | 7 +-- > drivers/gpu/drm/nouveau/dispnv50/disp.c | 12 +++-- > include/drm/display/drm_dp_mst_helper.h | 7 ++- > 5 files changed, 81 insertions(+), 31 deletions(-) > > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c > index d5cec03eaa8d..ec629b4037e4 100644 > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c > @@ -3263,6 +3263,7 @@ static void dm_handle_mst_sideband_msg(struct amdgpu_dm_connector *aconnector) > > while (dret == dpcd_bytes_to_read && > process_count < max_process_count) { > + u8 ack[DP_PSR_ERROR_STATUS - DP_SINK_COUNT_ESI] = {}; > u8 retry; > dret = 0; > > @@ -3271,28 +3272,29 @@ static void dm_handle_mst_sideband_msg(struct amdgpu_dm_connector *aconnector) > DRM_DEBUG_DRIVER("ESI %02x %02x %02x\n", esi[0], esi[1], esi[2]); > /* handle HPD short pulse irq */ > if (aconnector->mst_mgr.mst_state) > - drm_dp_mst_hpd_irq( > - &aconnector->mst_mgr, > - esi, > - &new_irq_handled); > + drm_dp_mst_hpd_irq_handle_event(&aconnector->mst_mgr, > + esi, > + ack, > + &new_irq_handled); > > if (new_irq_handled) { > /* ACK at DPCD to notify down stream */ > - const int ack_dpcd_bytes_to_write = > - dpcd_bytes_to_read - 1; > - > for (retry = 0; retry < 3; retry++) { > - u8 wret; > - > - wret = drm_dp_dpcd_write( > - &aconnector->dm_dp_aux.aux, > - dpcd_addr + 1, > - &esi[1], > - ack_dpcd_bytes_to_write); > - if (wret == ack_dpcd_bytes_to_write) > + ssize_t wret; > + > + wret = drm_dp_dpcd_writeb(&aconnector->dm_dp_aux.aux, > + dpcd_addr + 1, > + ack[1]); > + if (wret == 1) > break; > } > > + if (retry == 3) { > + DRM_ERROR("Failed to ack MST event.\n"); > + return; > + } > + > + drm_dp_mst_hpd_irq_send_new_request(&aconnector->mst_mgr); > /* check if there is new irq to be handled */ > dret = drm_dp_dpcd_read( > &aconnector->dm_dp_aux.aux, > diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c > index 38dab76ae69e..487d057a9582 100644 > --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c > +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c > @@ -4053,17 +4053,28 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr) > } > > /** > - * drm_dp_mst_hpd_irq() - MST hotplug IRQ notify > + * drm_dp_mst_hpd_irq_handle_event() - MST hotplug IRQ handle MST event > * @mgr: manager to notify irq for. > * @esi: 4 bytes from SINK_COUNT_ESI > + * @ack: 4 bytes used to ack events starting from SINK_COUNT_ESI > * @handled: whether the hpd interrupt was consumed or not > * > - * This should be called from the driver when it detects a short IRQ, > + * This should be called from the driver when it detects a HPD IRQ, > * along with the value of the DEVICE_SERVICE_IRQ_VECTOR_ESI0. The > - * topology manager will process the sideband messages received as a result > - * of this. > + * topology manager will process the sideband messages received > + * as indicated in the DEVICE_SERVICE_IRQ_VECTOR_ESI0 and set the > + * corresponding flags that Driver has to ack the DP receiver later. > + * > + * Note that driver shall also call > + * drm_dp_mst_hpd_irq_send_new_request() if the 'handled' is set > + * after calling this function, to try to kick off a new request in > + * the queue if the previous message transaction is completed. > + * > + * See also: > + * drm_dp_mst_hpd_irq_send_new_request() > */ > -int drm_dp_mst_hpd_irq(struct drm_dp_mst_topology_mgr *mgr, u8 *esi, bool *handled) > +int drm_dp_mst_hpd_irq_handle_event(struct drm_dp_mst_topology_mgr *mgr, const u8 *esi, > + u8 *ack, bool *handled) > { > int ret = 0; > int sc; > @@ -4078,18 +4089,47 @@ int drm_dp_mst_hpd_irq(struct drm_dp_mst_topology_mgr *mgr, u8 *esi, bool *handl > if (esi[1] & DP_DOWN_REP_MSG_RDY) { > ret = drm_dp_mst_handle_down_rep(mgr); > *handled = true; > + ack[1] |= DP_DOWN_REP_MSG_RDY; > } > > if (esi[1] & DP_UP_REQ_MSG_RDY) { > ret |= drm_dp_mst_handle_up_req(mgr); > *handled = true; > + ack[1] |= DP_UP_REQ_MSG_RDY; > } > > - drm_dp_mst_kick_tx(mgr); > return ret; > } > -EXPORT_SYMBOL(drm_dp_mst_hpd_irq); > +EXPORT_SYMBOL(drm_dp_mst_hpd_irq_handle_event); > > +/** > + * drm_dp_mst_hpd_irq_send_new_request() - MST hotplug IRQ kick off new request > + * @mgr: manager to notify irq for. > + * > + * This should be called from the driver when mst irq event is handled > + * and acked. Note that new down request should only be sent when > + * previous message transaction is completed. Source is not supposed to generate > + * interleaved message transactions. > + */ > +void drm_dp_mst_hpd_irq_send_new_request(struct drm_dp_mst_topology_mgr *mgr) > +{ > + struct drm_dp_sideband_msg_tx *txmsg; > + bool kick = true; > + > + mutex_lock(&mgr->qlock); > + txmsg = list_first_entry_or_null(&mgr->tx_msg_downq, > + struct drm_dp_sideband_msg_tx, next); > + /* If last transaction is not completed yet*/ > + if (!txmsg || > + txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND || > + txmsg->state == DRM_DP_SIDEBAND_TX_SENT) > + kick = false; > + mutex_unlock(&mgr->qlock); > + > + if (kick) > + drm_dp_mst_kick_tx(mgr); > +} > +EXPORT_SYMBOL(drm_dp_mst_hpd_irq_send_new_request); > /** > * drm_dp_mst_detect_port() - get connection status for an MST port > * @connector: DRM connector for this port > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c > index 4bec8cd7979f..f4a2e72a5c20 100644 > --- a/drivers/gpu/drm/i915/display/intel_dp.c > +++ b/drivers/gpu/drm/i915/display/intel_dp.c > @@ -4062,9 +4062,7 @@ intel_dp_mst_hpd_irq(struct intel_dp *intel_dp, u8 *esi, u8 *ack) > { > bool handled = false; > > - drm_dp_mst_hpd_irq(&intel_dp->mst_mgr, esi, &handled); > - if (handled) > - ack[1] |= esi[1] & (DP_DOWN_REP_MSG_RDY | DP_UP_REQ_MSG_RDY); > + drm_dp_mst_hpd_irq_handle_event(&intel_dp->mst_mgr, esi, ack, &handled); > > if (esi[1] & DP_CP_IRQ) { > intel_hdcp_handle_cp_irq(intel_dp->attached_connector); > @@ -4139,6 +4137,9 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp) > > if (!intel_dp_ack_sink_irq_esi(intel_dp, ack)) > drm_dbg_kms(&i915->drm, "Failed to ack ESI\n"); > + > + if (ack[1] & (DP_DOWN_REP_MSG_RDY | DP_UP_REQ_MSG_RDY)) > + drm_dp_mst_hpd_irq_send_new_request(&intel_dp->mst_mgr); > } > > return link_ok; > diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c > index 9b6824f6b9e4..42e1665ba11a 100644 > --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c > +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c > @@ -1359,22 +1359,26 @@ nv50_mstm_service(struct nouveau_drm *drm, > u8 esi[8] = {}; > > while (handled) { > + u8 ack[8] = {}; > + > rc = drm_dp_dpcd_read(aux, DP_SINK_COUNT_ESI, esi, 8); > if (rc != 8) { > ret = false; > break; > } > > - drm_dp_mst_hpd_irq(&mstm->mgr, esi, &handled); > + drm_dp_mst_hpd_irq_handle_event(&mstm->mgr, esi, ack, &handled); > if (!handled) > break; > > - rc = drm_dp_dpcd_write(aux, DP_SINK_COUNT_ESI + 1, &esi[1], > - 3); > - if (rc != 3) { > + rc = drm_dp_dpcd_writeb(aux, DP_SINK_COUNT_ESI + 1, ack[1]); > + > + if (rc != 1) { > ret = false; > break; > } > + > + drm_dp_mst_hpd_irq_send_new_request(&mstm->mgr); > } > > if (!ret) > diff --git a/include/drm/display/drm_dp_mst_helper.h b/include/drm/display/drm_dp_mst_helper.h > index 32c764fb9cb5..40e855c8407c 100644 > --- a/include/drm/display/drm_dp_mst_helper.h > +++ b/include/drm/display/drm_dp_mst_helper.h > @@ -815,8 +815,11 @@ void drm_dp_mst_topology_mgr_destroy(struct drm_dp_mst_topology_mgr *mgr); > bool drm_dp_read_mst_cap(struct drm_dp_aux *aux, const u8 dpcd[DP_RECEIVER_CAP_SIZE]); > int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool mst_state); > > -int drm_dp_mst_hpd_irq(struct drm_dp_mst_topology_mgr *mgr, u8 *esi, bool *handled); > - > +int drm_dp_mst_hpd_irq_handle_event(struct drm_dp_mst_topology_mgr *mgr, > + const u8 *esi, > + u8 *ack, > + bool *handled); > +void drm_dp_mst_hpd_irq_send_new_request(struct drm_dp_mst_topology_mgr *mgr); > > int > drm_dp_mst_detect_port(struct drm_connector *connector, -- Cheers, Lyude Paul (she/her) Software Engineer at Red Hat