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Date:   Tue, 15 Feb 2022 16:40:35 -0600
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Subject: Re: [PATCH v3 24/25] bus: mhi: ep: Add support for suspending and
 resuming channels
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To:     Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
        mhi@lists.linux.dev
Cc:     quic_hemantk@quicinc.com, quic_bbhatt@quicinc.com,
        quic_jhugo@quicinc.com, vinod.koul@linaro.org,
        bjorn.andersson@linaro.org, dmitry.baryshkov@linaro.org,
        quic_vbadigan@quicinc.com, quic_cang@quicinc.com,
        quic_skananth@quicinc.com, linux-arm-msm@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20220212182117.49438-1-manivannan.sadhasivam@linaro.org>
 <20220212182117.49438-25-manivannan.sadhasivam@linaro.org>
From:   Alex Elder <elder@linaro.org>
In-Reply-To: <20220212182117.49438-25-manivannan.sadhasivam@linaro.org>
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On 2/12/22 12:21 PM, Manivannan Sadhasivam wrote:
> Add support for suspending and resuming the channels in MHI endpoint stack.
> The channels will be moved to the suspended state during M3 state
> transition and will be resumed during M0 transition.
> 
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Looks good.

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

> ---
>   drivers/bus/mhi/ep/internal.h |  2 ++
>   drivers/bus/mhi/ep/main.c     | 58 +++++++++++++++++++++++++++++++++++
>   drivers/bus/mhi/ep/sm.c       |  4 +++
>   3 files changed, 64 insertions(+)
> 
> diff --git a/drivers/bus/mhi/ep/internal.h b/drivers/bus/mhi/ep/internal.h
> index 8654af7caf40..e23d2fd04282 100644
> --- a/drivers/bus/mhi/ep/internal.h
> +++ b/drivers/bus/mhi/ep/internal.h
> @@ -242,6 +242,8 @@ int mhi_ep_set_m0_state(struct mhi_ep_cntrl *mhi_cntrl);
>   int mhi_ep_set_m3_state(struct mhi_ep_cntrl *mhi_cntrl);
>   int mhi_ep_set_ready_state(struct mhi_ep_cntrl *mhi_cntrl);
>   void mhi_ep_handle_syserr(struct mhi_ep_cntrl *mhi_cntrl);
> +void mhi_ep_resume_channels(struct mhi_ep_cntrl *mhi_cntrl);
> +void mhi_ep_suspend_channels(struct mhi_ep_cntrl *mhi_cntrl);
>   
>   /* MHI EP memory management functions */
>   int mhi_ep_alloc_map(struct mhi_ep_cntrl *mhi_cntrl, u64 pci_addr, size_t size,
> diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
> index e4186b012257..315409705b91 100644
> --- a/drivers/bus/mhi/ep/main.c
> +++ b/drivers/bus/mhi/ep/main.c
> @@ -1106,6 +1106,64 @@ void mhi_ep_power_down(struct mhi_ep_cntrl *mhi_cntrl)
>   }
>   EXPORT_SYMBOL_GPL(mhi_ep_power_down);
>   
> +void mhi_ep_suspend_channels(struct mhi_ep_cntrl *mhi_cntrl)
> +{
> +	struct mhi_ep_chan *mhi_chan;
> +	u32 tmp;
> +	int i;
> +
> +	for (i = 0; i < mhi_cntrl->max_chan; i++) {
> +		mhi_chan = &mhi_cntrl->mhi_chan[i];
> +
> +		if (!mhi_chan->mhi_dev)
> +			continue;
> +
> +		mutex_lock(&mhi_chan->lock);
> +		/* Skip if the channel is not currently running */
> +		tmp = le32_to_cpu(mhi_cntrl->ch_ctx_cache[i].chcfg);
> +		if (FIELD_GET(CHAN_CTX_CHSTATE_MASK, tmp) != MHI_CH_STATE_RUNNING) {
> +			mutex_unlock(&mhi_chan->lock);
> +			continue;
> +		}
> +
> +		dev_dbg(&mhi_chan->mhi_dev->dev, "Suspending channel\n");
> +		/* Set channel state to SUSPENDED */
> +		tmp &= ~CHAN_CTX_CHSTATE_MASK;
> +		tmp |= FIELD_PREP(CHAN_CTX_CHSTATE_MASK, MHI_CH_STATE_SUSPENDED);

Somebody really needs to write a FIELD_UPDATE() macro to
do this read/modify/write pattern.

> +		mhi_cntrl->ch_ctx_cache[i].chcfg = cpu_to_le32(tmp);
> +		mutex_unlock(&mhi_chan->lock);
> +	}
> +}
> +
> +void mhi_ep_resume_channels(struct mhi_ep_cntrl *mhi_cntrl)
> +{
> +	struct mhi_ep_chan *mhi_chan;
> +	u32 tmp;
> +	int i;
> +
> +	for (i = 0; i < mhi_cntrl->max_chan; i++) {
> +		mhi_chan = &mhi_cntrl->mhi_chan[i];
> +
> +		if (!mhi_chan->mhi_dev)
> +			continue;
> +
> +		mutex_lock(&mhi_chan->lock);
> +		/* Skip if the channel is not currently suspended */
> +		tmp = le32_to_cpu(mhi_cntrl->ch_ctx_cache[i].chcfg);
> +		if (FIELD_GET(CHAN_CTX_CHSTATE_MASK, tmp) != MHI_CH_STATE_SUSPENDED) {
> +			mutex_unlock(&mhi_chan->lock);
> +			continue;
> +		}
> +
> +		dev_dbg(&mhi_chan->mhi_dev->dev, "Resuming channel\n");
> +		/* Set channel state to RUNNING */
> +		tmp &= ~CHAN_CTX_CHSTATE_MASK;
> +		tmp |= FIELD_PREP(CHAN_CTX_CHSTATE_MASK, MHI_CH_STATE_RUNNING);
> +		mhi_cntrl->ch_ctx_cache[i].chcfg = cpu_to_le32(tmp);
> +		mutex_unlock(&mhi_chan->lock);
> +	}
> +}
> +
>   static void mhi_ep_release_device(struct device *dev)
>   {
>   	struct mhi_ep_device *mhi_dev = to_mhi_ep_device(dev);
> diff --git a/drivers/bus/mhi/ep/sm.c b/drivers/bus/mhi/ep/sm.c
> index 9a75ecfe1adf..e24ba2d85e13 100644
> --- a/drivers/bus/mhi/ep/sm.c
> +++ b/drivers/bus/mhi/ep/sm.c
> @@ -88,8 +88,11 @@ int mhi_ep_set_m0_state(struct mhi_ep_cntrl *mhi_cntrl)
>   	enum mhi_state old_state;
>   	int ret;
>   
> +	/* If MHI is in M3, resume suspended channels */
>   	spin_lock_bh(&mhi_cntrl->state_lock);
>   	old_state = mhi_cntrl->mhi_state;
> +	if (old_state == MHI_STATE_M3)
> +		mhi_ep_resume_channels(mhi_cntrl);
>   
>   	ret = mhi_ep_set_mhi_state(mhi_cntrl, MHI_STATE_M0);
>   	if (ret) {
> @@ -135,6 +138,7 @@ int mhi_ep_set_m3_state(struct mhi_ep_cntrl *mhi_cntrl)
>   	}
>   
>   	spin_unlock_bh(&mhi_cntrl->state_lock);
> +	mhi_ep_suspend_channels(mhi_cntrl);
>   
>   	/* Signal host that the device moved to M3 */
>   	ret = mhi_ep_send_state_change_event(mhi_cntrl, MHI_STATE_M3);