[PATCH 15/20] bus: mhi: ep: Add support for handling MHI_RESET

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

Add support for handling MHI_RESET in MHI endpoint stack. MHI_RESET will
be issued by the host during shutdown and during error scenario so that
it can recover the endpoint device without restarting the whole device.

MHI_RESET handling involves resetting the internal MHI registers, data
structures, state machines, resetting all channels/rings and setting
MHICTRL.RESET bit to 0. Additionally the device will also move to READY
state if the reset was due to SYS_ERR.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
---
 drivers/bus/mhi/ep/main.c | 53 +++++++++++++++++++++++++++++++++++++++
 include/linux/mhi_ep.h    |  2 ++
 2 files changed, 55 insertions(+)

diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
index 89d1bb780747..0b0fad6bf69a 100644
--- a/drivers/bus/mhi/ep/main.c
+++ b/drivers/bus/mhi/ep/main.c
@@ -464,6 +464,7 @@ static irqreturn_t mhi_ep_irq(int irq, void *data)
 	struct device *dev = &mhi_cntrl->mhi_dev->dev;
 	enum mhi_state state;
 	u32 int_value = 0;
+	bool mhi_reset;
 
 	/* Acknowledge the interrupts */
 	mhi_ep_mmio_read(mhi_cntrl, MHI_CTRL_INT_STATUS_A7, &int_value);
@@ -472,6 +473,14 @@ static irqreturn_t mhi_ep_irq(int irq, void *data)
 	/* Check for ctrl interrupt */
 	if (FIELD_GET(MHI_CTRL_INT_STATUS_A7_MSK, int_value)) {
 		dev_dbg(dev, "Processing ctrl interrupt\n");
+		mhi_ep_mmio_get_mhi_state(mhi_cntrl, &state, &mhi_reset);
+		if (mhi_reset) {
+			dev_info(dev, "Host triggered MHI reset!\n");
+			disable_irq_nosync(mhi_cntrl->irq);
+			schedule_work(&mhi_cntrl->reset_work);
+			return IRQ_HANDLED;
+		}
+
 		mhi_ep_process_ctrl_interrupt(mhi_cntrl, state);
 	}
 
@@ -552,6 +561,49 @@ static void mhi_ep_abort_transfer(struct mhi_ep_cntrl *mhi_cntrl)
 	mhi_cntrl->is_enabled = false;
 }
 
+static void mhi_ep_reset_worker(struct work_struct *work)
+{
+	struct mhi_ep_cntrl *mhi_cntrl = container_of(work, struct mhi_ep_cntrl, reset_work);
+	struct device *dev = &mhi_cntrl->mhi_dev->dev;
+	enum mhi_state cur_state;
+	int ret;
+
+	mhi_ep_abort_transfer(mhi_cntrl);
+
+	spin_lock_bh(&mhi_cntrl->state_lock);
+	/* Reset MMIO to signal host that the MHI_RESET is completed in endpoint */
+	mhi_ep_mmio_reset(mhi_cntrl);
+	cur_state = mhi_cntrl->mhi_state;
+	spin_unlock_bh(&mhi_cntrl->state_lock);
+
+	/*
+	 * Only proceed further if the reset is due to SYS_ERR. The host will
+	 * issue reset during shutdown also and we don't need to do re-init in
+	 * that case.
+	 */
+	if (cur_state == MHI_STATE_SYS_ERR) {
+		mhi_ep_mmio_init(mhi_cntrl);
+
+		/* Set AMSS EE before signaling ready state */
+		mhi_ep_mmio_set_env(mhi_cntrl, MHI_EP_AMSS_EE);
+
+		/* All set, notify the host that we are ready */
+		ret = mhi_ep_set_ready_state(mhi_cntrl);
+		if (ret)
+			return;
+
+		dev_dbg(dev, "READY state notification sent to the host\n");
+
+		ret = mhi_ep_enable(mhi_cntrl);
+		if (ret) {
+			dev_err(dev, "Failed to enable MHI endpoint: %d\n", ret);
+			return;
+		}
+
+		enable_irq(mhi_cntrl->irq);
+	}
+}
+
 int mhi_ep_power_up(struct mhi_ep_cntrl *mhi_cntrl)
 {
 	struct device *dev = &mhi_cntrl->mhi_dev->dev;
@@ -824,6 +876,7 @@ int mhi_ep_register_controller(struct mhi_ep_cntrl *mhi_cntrl,
 
 	INIT_WORK(&mhi_cntrl->ring_work, mhi_ep_ring_worker);
 	INIT_WORK(&mhi_cntrl->state_work, mhi_ep_state_worker);
+	INIT_WORK(&mhi_cntrl->reset_work, mhi_ep_reset_worker);
 
 	mhi_cntrl->ring_wq = alloc_ordered_workqueue("mhi_ep_ring_wq", WQ_HIGHPRI);
 	if (!mhi_cntrl->ring_wq) {
diff --git a/include/linux/mhi_ep.h b/include/linux/mhi_ep.h
index 57fa445661f6..6482b0c91865 100644
--- a/include/linux/mhi_ep.h
+++ b/include/linux/mhi_ep.h
@@ -75,6 +75,7 @@ struct mhi_ep_db_info {
  * @ring_wq: Dedicated workqueue for processing MHI rings
  * @state_work: State transition worker
  * @ring_work: Ring worker
+ * @reset_work: Worker for MHI Endpoint reset
  * @ch_db_list: List of queued channel doorbells
  * @st_transition_list: List of state transitions
  * @list_lock: Lock for protecting state transition and channel doorbell lists
@@ -123,6 +124,7 @@ struct mhi_ep_cntrl {
 	struct workqueue_struct	*ring_wq;
 	struct work_struct state_work;
 	struct work_struct ring_work;
+	struct work_struct reset_work;
 
 	struct list_head ch_db_list;
 	struct list_head st_transition_list;
-- 
2.25.1