linux-kernel - Re: [PATCH v3 17/25] bus: mhi: ep: Add support for powering down the MHI endpoint stack

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Date:   Tue, 15 Feb 2022 16:39:43 -0600
From:   Alex Elder <elder@...aro.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        mhi@...ts.linux.dev
Cc:     quic_hemantk@...cinc.com, quic_bbhatt@...cinc.com,
        quic_jhugo@...cinc.com, vinod.koul@...aro.org,
        bjorn.andersson@...aro.org, dmitry.baryshkov@...aro.org,
        quic_vbadigan@...cinc.com, quic_cang@...cinc.com,
        quic_skananth@...cinc.com, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 17/25] bus: mhi: ep: Add support for powering down the
 MHI endpoint stack

On 2/12/22 12:21 PM, Manivannan Sadhasivam wrote:
> Add support for MHI endpoint power_down that includes stopping all
> available channels, destroying the channels, resetting the event and
> transfer rings and freeing the host cache.
> 
> The stack will be powered down whenever the physical bus link goes down.
> 
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

Not much to say here either, just a few suggestions.

					-Alex

> ---
>   drivers/bus/mhi/ep/main.c | 81 +++++++++++++++++++++++++++++++++++++++
>   include/linux/mhi_ep.h    |  6 +++
>   2 files changed, 87 insertions(+)
> 
> diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
> index 016e819f640a..14cb08de4263 100644
> --- a/drivers/bus/mhi/ep/main.c
> +++ b/drivers/bus/mhi/ep/main.c
> @@ -21,6 +21,8 @@
>   
>   static DEFINE_IDA(mhi_ep_cntrl_ida);
>   
> +static int mhi_ep_destroy_device(struct device *dev, void *data);
> +
>   static int mhi_ep_send_event(struct mhi_ep_cntrl *mhi_cntrl, u32 ring_idx,
>   			     struct mhi_ep_ring_element *el)
>   {
> @@ -492,6 +494,71 @@ static irqreturn_t mhi_ep_irq(int irq, void *data)
>   	return IRQ_HANDLED;
>   }
>   
> +static void mhi_ep_abort_transfer(struct mhi_ep_cntrl *mhi_cntrl)
> +{
> +	struct mhi_ep_ring *ch_ring, *ev_ring;
> +	struct mhi_result result = {};
> +	struct mhi_ep_chan *mhi_chan;
> +	int i;
> +
> +	/* Stop all the channels */
> +	for (i = 0; i < mhi_cntrl->max_chan; i++) {
		mhi_chan = &mhi_cntrl->mhi_chan[i];
		ch_ring = &mhi_chan->ring;
	
> +		ch_ring = &mhi_cntrl->mhi_chan[i].ring;
> +		if (!ch_ring->started)
> +			continue;
> +
> +		mhi_chan = &mhi_cntrl->mhi_chan[i];
> +		mutex_lock(&mhi_chan->lock);
> +		/* Send channel disconnect status to client drivers */
> +		if (mhi_chan->xfer_cb) {
> +			result.transaction_status = -ENOTCONN;
> +			result.bytes_xferd = 0;
> +			mhi_chan->xfer_cb(mhi_chan->mhi_dev, &result);
> +		}
> +
> +		/* Set channel state to DISABLED */

Omit the above comment.

> +		mhi_chan->state = MHI_CH_STATE_DISABLED;
> +		mutex_unlock(&mhi_chan->lock);
> +	}
> +
> +	flush_workqueue(mhi_cntrl->ring_wq);
> +	flush_workqueue(mhi_cntrl->state_wq);
> +
> +	/* Destroy devices associated with all channels */
> +	device_for_each_child(&mhi_cntrl->mhi_dev->dev, NULL, mhi_ep_destroy_device);
> +
> +	/* Stop and reset the transfer rings */
> +	for (i = 0; i < mhi_cntrl->max_chan; i++) {
		mhi_chan = ...

		if (!mhi_chan->ring.started)
			continue;

> +		ch_ring = &mhi_cntrl->mhi_chan[i].ring;
> +		if (!ch_ring->started)
> +			continue;
> +
> +		mhi_chan = &mhi_cntrl->mhi_chan[i];
> +		mutex_lock(&mhi_chan->lock);
> +		mhi_ep_ring_reset(mhi_cntrl, ch_ring);
> +		mutex_unlock(&mhi_chan->lock);
> +	}
> +
> +	/* Stop and reset the event rings */
> +	for (i = 0; i < mhi_cntrl->event_rings; i++) {
> +		ev_ring = &mhi_cntrl->mhi_event[i].ring;
> +		if (!ev_ring->started)
> +			continue;
> +
> +		mutex_lock(&mhi_cntrl->event_lock);
> +		mhi_ep_ring_reset(mhi_cntrl, ev_ring);
> +		mutex_unlock(&mhi_cntrl->event_lock);
> +	}
> +
> +	/* Stop and reset the command ring */
> +	mhi_ep_ring_reset(mhi_cntrl, &mhi_cntrl->mhi_cmd->ring);
> +
> +	mhi_ep_free_host_cfg(mhi_cntrl);
> +	mhi_ep_mmio_mask_interrupts(mhi_cntrl);
> +
> +	mhi_cntrl->is_enabled = false;
> +}
> +
>   int mhi_ep_power_up(struct mhi_ep_cntrl *mhi_cntrl)
>   {
>   	struct device *dev = &mhi_cntrl->mhi_dev->dev;
> @@ -548,6 +615,16 @@ int mhi_ep_power_up(struct mhi_ep_cntrl *mhi_cntrl)
>   }
>   EXPORT_SYMBOL_GPL(mhi_ep_power_up);
>   
> +void mhi_ep_power_down(struct mhi_ep_cntrl *mhi_cntrl)
> +{
> +	if (mhi_cntrl->is_enabled)
> +		mhi_ep_abort_transfer(mhi_cntrl);
> +
> +	kfree(mhi_cntrl->mhi_event);
> +	disable_irq(mhi_cntrl->irq);
> +}
> +EXPORT_SYMBOL_GPL(mhi_ep_power_down);
> +
>   static void mhi_ep_release_device(struct device *dev)
>   {
>   	struct mhi_ep_device *mhi_dev = to_mhi_ep_device(dev);
> @@ -828,6 +905,10 @@ int mhi_ep_register_controller(struct mhi_ep_cntrl *mhi_cntrl,
>   }
>   EXPORT_SYMBOL_GPL(mhi_ep_register_controller);
>   
> +/*
> + * It is expected that the controller drivers will power down the MHI EP stack
> + * using "mhi_ep_power_down()" before calling this function to unregister themselves.
> + */
>   void mhi_ep_unregister_controller(struct mhi_ep_cntrl *mhi_cntrl)
>   {
>   	struct mhi_ep_device *mhi_dev = mhi_cntrl->mhi_dev;
> diff --git a/include/linux/mhi_ep.h b/include/linux/mhi_ep.h
> index 53895f1c68e1..4f86e7986c93 100644
> --- a/include/linux/mhi_ep.h
> +++ b/include/linux/mhi_ep.h
> @@ -260,4 +260,10 @@ void mhi_ep_unregister_controller(struct mhi_ep_cntrl *mhi_cntrl);
>    */
>   int mhi_ep_power_up(struct mhi_ep_cntrl *mhi_cntrl);
>   
> +/**
> + * mhi_ep_power_down - Power down the MHI endpoint stack
> + * @mhi_cntrl: MHI controller
> + */
> +void mhi_ep_power_down(struct mhi_ep_cntrl *mhi_cntrl);
> +
>   #endif