linux-kernel - Re: [PATCH v3 20/25] bus: mhi: ep: Add support for processing command ring

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Message-ID: <20220222103502.GF5029@thinkpad>
Date:   Tue, 22 Feb 2022 16:05:02 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Alex Elder <elder@...aro.org>
Cc:     mhi@...ts.linux.dev, 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 20/25] bus: mhi: ep: Add support for processing
 command ring

On Tue, Feb 15, 2022 at 04:40:01PM -0600, Alex Elder wrote:
> On 2/12/22 12:21 PM, Manivannan Sadhasivam wrote:
> > Add support for processing the command ring. Command ring is used by the
> > host to issue channel specific commands to the ep device. Following
> > commands are supported:
> > 
> > 1. Start channel
> > 2. Stop channel
> > 3. Reset channel
> > 
> > Once the device receives the command doorbell interrupt from host, it
> > executes the command and generates a command completion event to the
> > host in the primary event ring.
> > 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> 
> I'll let you consider my few comments below, but whether or not you
> address them, this looks OK to me.
> 
> Reviewed-by: Alex Elder <elder@...aro.org>
> 
> > ---
> >   drivers/bus/mhi/ep/main.c | 151 ++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 151 insertions(+)
> > 
> > diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
> > index 6378ac5c7e37..4c2ee517832c 100644
> > --- a/drivers/bus/mhi/ep/main.c
> > +++ b/drivers/bus/mhi/ep/main.c
> > @@ -21,6 +21,7 @@
> >   static DEFINE_IDA(mhi_ep_cntrl_ida);
> > +static int mhi_ep_create_device(struct mhi_ep_cntrl *mhi_cntrl, u32 ch_id);
> >   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,
> > @@ -185,6 +186,156 @@ void mhi_ep_unmap_free(struct mhi_ep_cntrl *mhi_cntrl, u64 pci_addr, phys_addr_t
> >   	mhi_cntrl->free_addr(mhi_cntrl, phys - offset, virt - offset, size);
> >   }
> > +int mhi_ep_process_cmd_ring(struct mhi_ep_ring *ring, struct mhi_ep_ring_element *el)
> > +{
> > +	struct mhi_ep_cntrl *mhi_cntrl = ring->mhi_cntrl;
> > +	struct device *dev = &mhi_cntrl->mhi_dev->dev;
> > +	struct mhi_result result = {};
> > +	struct mhi_ep_chan *mhi_chan;
> > +	struct mhi_ep_ring *ch_ring;
> > +	u32 tmp, ch_id;
> > +	int ret;
> > +
> > +	ch_id = MHI_TRE_GET_CMD_CHID(el);
> > +	mhi_chan = &mhi_cntrl->mhi_chan[ch_id];
> > +	ch_ring = &mhi_cntrl->mhi_chan[ch_id].ring;
> > +
> > +	switch (MHI_TRE_GET_CMD_TYPE(el)) {
> 
> No MHI_PKT_TYPE_NOOP_CMD?
> 

Not now.

> > +	case MHI_PKT_TYPE_START_CHAN_CMD:
> > +		dev_dbg(dev, "Received START command for channel (%d)\n", ch_id);
> > +
> > +		mutex_lock(&mhi_chan->lock);
> > +		/* Initialize and configure the corresponding channel ring */
> > +		if (!ch_ring->started) {
> > +			ret = mhi_ep_ring_start(mhi_cntrl, ch_ring,
> > +				(union mhi_ep_ring_ctx *)&mhi_cntrl->ch_ctx_cache[ch_id]);
> > +			if (ret) {
> > +				dev_err(dev, "Failed to start ring for channel (%d)\n", ch_id);
> > +				ret = mhi_ep_send_cmd_comp_event(mhi_cntrl,
> > +							MHI_EV_CC_UNDEFINED_ERR);
> > +				if (ret)
> > +					dev_err(dev, "Error sending completion event (%d)\n",
> > +						MHI_EV_CC_UNDEFINED_ERR);
> 
> Print the value of ret in the above message (not UNDEFINED_ERR).
> 
> > +
> > +				goto err_unlock;
> > +			}
> > +		}
> > +
> > +		/* Enable DB for the channel */
> > +		mhi_ep_mmio_enable_chdb_a7(mhi_cntrl, ch_id);
> 
> If an error occurs later, this will be enabled.  Is that what
> you want?  Maybe wait to enable the doorbell until everything
> else succeeds.
> 

Makes sense. Will move this to the end.

> > +
> > +		/* Set channel state to RUNNING */
> > +		mhi_chan->state = MHI_CH_STATE_RUNNING;
> > +		tmp = le32_to_cpu(mhi_cntrl->ch_ctx_cache[ch_id].chcfg);
> > +		tmp &= ~CHAN_CTX_CHSTATE_MASK;
> > +		tmp |= FIELD_PREP(CHAN_CTX_CHSTATE_MASK, MHI_CH_STATE_RUNNING);
> > +		mhi_cntrl->ch_ctx_cache[ch_id].chcfg = cpu_to_le32(tmp);
> > +
> > +		ret = mhi_ep_send_cmd_comp_event(mhi_cntrl, MHI_EV_CC_SUCCESS);
> > +		if (ret) {
> > +			dev_err(dev, "Error sending command completion event (%d)\n",
> > +				MHI_EV_CC_SUCCESS);
> > +			goto err_unlock;
> > +		}
> > +
> > +		mutex_unlock(&mhi_chan->lock);
> > +
> > +		/*
> > +		 * Create MHI device only during UL channel start. Since the MHI
> > +		 * channels operate in a pair, we'll associate both UL and DL
> > +		 * channels to the same device.
> > +		 *
> > +		 * We also need to check for mhi_dev != NULL because, the host
> > +		 * will issue START_CHAN command during resume and we don't
> > +		 * destroy the device during suspend.
> > +		 */
> > +		if (!(ch_id % 2) && !mhi_chan->mhi_dev) {
> > +			ret = mhi_ep_create_device(mhi_cntrl, ch_id);
> > +			if (ret) {
> 
> If this occurs, the host will already have been told the
> request completed successfully.  Is that a problem that
> can/should be avoided?
> 

This should result in SYSERR. Will handle.

Thanks,
Mani