bus: mhi: ep: Add support for handling MHI_RESET

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.

Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20220405135754.6622-12-manivannan.sadhasivam@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
index 968025e..d36708d 100644 (file)
--- a/drivers/bus/mhi/ep/main.c
+++ b/drivers/bus/mhi/ep/main.c
@@ -381,6 +381,7 @@ 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 ctrl interrupt */
        int_value = mhi_ep_mmio_read(mhi_cntrl, MHI_CTRL_INT_STATUS);
@@ -389,6 +390,14 @@ static irqreturn_t mhi_ep_irq(int irq, void *data)
        /* Check for ctrl interrupt */
        if (FIELD_GET(MHI_CTRL_INT_STATUS_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);
        }
 
@@ -464,6 +473,49 @@ static void mhi_ep_abort_transfer(struct mhi_ep_cntrl *mhi_cntrl)
        mhi_cntrl->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_EE_AMSS);
+
+               /* 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;
@@ -738,6 +790,7 @@ int mhi_ep_register_controller(struct mhi_ep_cntrl *mhi_cntrl,
        }
 
        INIT_WORK(&mhi_cntrl->state_work, mhi_ep_state_worker);
+       INIT_WORK(&mhi_cntrl->reset_work, mhi_ep_reset_worker);
 
        mhi_cntrl->wq = alloc_workqueue("mhi_ep_wq", 0, 0);
        if (!mhi_cntrl->wq) {

diff --git a/include/linux/mhi_ep.h b/include/linux/mhi_ep.h
index 9da683e..2f31a54 100644 (file)
--- a/include/linux/mhi_ep.h
+++ b/include/linux/mhi_ep.h
@@ -76,6 +76,7 @@ struct mhi_ep_db_info {
  * @ch_db_list: List of queued channel doorbells
  * @wq: Dedicated workqueue for handling rings and state changes
  * @state_work: State transition worker
+ * @reset_work: Worker for MHI Endpoint reset
  * @raise_irq: CB function for raising IRQ to the host
  * @alloc_map: CB function for allocating memory in endpoint for storing host context and mapping it
  * @unmap_free: CB function to unmap and free the allocated memory in endpoint for storing host context
@@ -122,6 +123,7 @@ struct mhi_ep_cntrl {
 
        struct workqueue_struct *wq;
        struct work_struct state_work;
+       struct work_struct reset_work;
 
        void (*raise_irq)(struct mhi_ep_cntrl *mhi_cntrl, u32 vector);
        int (*alloc_map)(struct mhi_ep_cntrl *mhi_cntrl, u64 pci_addr, phys_addr_t *phys_ptr,