bus: mhi: ep: Add support for handling SYS_ERR condition

Add support for handling SYS_ERR (System Error) condition in the MHI
endpoint stack. The SYS_ERR flag will be asserted by the endpoint device
when it detects an internal error. The host will then issue reset and
reinitializes MHI to recover from the error state.
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

drivers/bus/mhi/ep/internal.h

@@ -211,5 +211,6 @@ int mhi_ep_set_mhi_state(struct mhi_ep_cntrl *mhi_cntrl, enum mhi_state mhi_stat
 int mhi_ep_set_m0_state(struct mhi_ep_cntrl *mhi_cntrl);
 int mhi_ep_set_m3_state(struct mhi_ep_cntrl *mhi_cntrl);
 int mhi_ep_set_ready_state(struct mhi_ep_cntrl *mhi_cntrl);
+void mhi_ep_handle_syserr(struct mhi_ep_cntrl *mhi_cntrl);
 
 #endif

drivers/bus/mhi/ep/main.c

@@ -516,6 +516,26 @@ static void mhi_ep_reset_worker(struct work_struct *work)
 	}
 }
 
+/*
+ * We don't need to do anything special other than setting the MHI SYS_ERR
+ * state. The host will reset all contexts and issue MHI RESET so that we
+ * could also recover from error state.
+ */
+void mhi_ep_handle_syserr(struct mhi_ep_cntrl *mhi_cntrl)
+{
+	struct device *dev = &mhi_cntrl->mhi_dev->dev;
+	int ret;
+
+	ret = mhi_ep_set_mhi_state(mhi_cntrl, MHI_STATE_SYS_ERR);
+	if (ret)
+		return;
+
+	/* Signal host that the device went to SYS_ERR state */
+	ret = mhi_ep_send_state_change_event(mhi_cntrl, MHI_STATE_SYS_ERR);
+	if (ret)
+		dev_err(dev, "Failed sending SYS_ERR state change event: %d\n", ret);
+}
+
 int mhi_ep_power_up(struct mhi_ep_cntrl *mhi_cntrl)
 {
 	struct device *dev = &mhi_cntrl->mhi_dev->dev;

drivers/bus/mhi/ep/sm.c

@@ -68,8 +68,10 @@ int mhi_ep_set_m0_state(struct mhi_ep_cntrl *mhi_cntrl)
 	ret = mhi_ep_set_mhi_state(mhi_cntrl, MHI_STATE_M0);
 	spin_unlock_bh(&mhi_cntrl->state_lock);
 
-	if (ret)
+	if (ret) {
+		mhi_ep_handle_syserr(mhi_cntrl);
 		return ret;
+	}
 
 	/* Signal host that the device moved to M0 */
 	ret = mhi_ep_send_state_change_event(mhi_cntrl, MHI_STATE_M0);
@@ -99,8 +101,10 @@ int mhi_ep_set_m3_state(struct mhi_ep_cntrl *mhi_cntrl)
 	ret = mhi_ep_set_mhi_state(mhi_cntrl, MHI_STATE_M3);
 	spin_unlock_bh(&mhi_cntrl->state_lock);
 
-	if (ret)
+	if (ret) {
+		mhi_ep_handle_syserr(mhi_cntrl);
 		return ret;
+	}
 
 	/* Signal host that the device moved to M3 */
 	ret = mhi_ep_send_state_change_event(mhi_cntrl, MHI_STATE_M3);
@@ -132,5 +136,8 @@ int mhi_ep_set_ready_state(struct mhi_ep_cntrl *mhi_cntrl)
 	ret = mhi_ep_set_mhi_state(mhi_cntrl, MHI_STATE_READY);
 	spin_unlock_bh(&mhi_cntrl->state_lock);
 
+	if (ret)
+		mhi_ep_handle_syserr(mhi_cntrl);
+
 	return ret;
 }