[v3,18/25] 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.

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(+)

On 2/12/22 12:21 PM, Manivannan Sadhasivam wrote:
> 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>

I might be getting tired out...  But this looks good to me!

Reviewed-by: Alex Elder <elder@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;