[PATCH v3 18/25] bus: mhi: ep: Add support for handling MHI_RESET

Manivannan Sadhasivam
2022-02-12T18:23:29Z

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 14cb08de4263..ddedd0fb19aa 100644
--- a/drivers/bus/mhi/ep/main.c
+++ b/drivers/bus/mhi/ep/main.c
@@ -471,6 +471,7 @@ 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;
+ bool mhi_reset;

/* Acknowledge the interrupts */
int_value = mhi_ep_mmio_read(mhi_cntrl, MHI_CTRL_INT_STATUS_A7);
@@ -479,6 +480,14 @@ 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);
}

@@ -559,6 +568,49 @@ 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;
@@ -827,6 +879,7 @@ 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_workqueue("mhi_ep_ring_wq", 0, 0);
if (!mhi_cntrl->ring_wq) {
diff --git a/include/linux/mhi_ep.h b/include/linux/mhi_ep.h
index 4f86e7986c93..276d29fef465 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
@@ -126,6 +127,7 @@ 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