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    SubjectRe: [PATCH v4 19/27] bus: mhi: ep: Add support for powering down the MHI endpoint stack
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    On 2/28/22 6:43 AM, 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@linaro.org>

    Looks good.

    Reviewed-by: Alex Elder <elder@linaro.org>

    > ---
    > drivers/bus/mhi/ep/main.c | 78 +++++++++++++++++++++++++++++++++++++++
    > include/linux/mhi_ep.h | 6 +++
    > 2 files changed, 84 insertions(+)
    >
    > diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
    > index 47807102baad..4956440273ad 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_ring_element *el, bool bei)
    > {
    > @@ -432,6 +434,68 @@ 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];
    > + if (!mhi_chan->ring.started)
    > + continue;
    > +
    > + 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);
    > + }
    > +
    > + mhi_chan->state = MHI_CH_STATE_DISABLED;
    > + mutex_unlock(&mhi_chan->lock);
    > + }
    > +
    > + flush_workqueue(mhi_cntrl->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 = &mhi_cntrl->mhi_chan[i];
    > + if (!mhi_chan->ring.started)
    > + continue;
    > +
    > + ch_ring = &mhi_cntrl->mhi_chan[i].ring;
    > + 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->enabled = false;
    > +}
    > +
    > int mhi_ep_power_up(struct mhi_ep_cntrl *mhi_cntrl)
    > {
    > struct device *dev = &mhi_cntrl->mhi_dev->dev;
    > @@ -486,6 +550,16 @@ 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->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);
    > @@ -765,6 +839,10 @@ 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 1b7dec859a5e..8e062a4c84f4 100644
    > --- a/include/linux/mhi_ep.h
    > +++ b/include/linux/mhi_ep.h
    > @@ -251,4 +251,10 @@ 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

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