linux-kernel - Re: [PATCH v8 5/9] bus: mhi: core: Hold device wake for channel update commands

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Date:   Wed, 7 Apr 2021 12:01:28 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Bhaumik Bhatt <bbhatt@...eaurora.org>
Cc:     linux-arm-msm@...r.kernel.org, hemantk@...eaurora.org,
        jhugo@...eaurora.org, linux-kernel@...r.kernel.org,
        carl.yin@...ctel.com, naveen.kumar@...ctel.com,
        loic.poulain@...aro.org
Subject: Re: [PATCH v8 5/9] bus: mhi: core: Hold device wake for channel
 update commands

On Thu, Apr 01, 2021 at 02:16:14PM -0700, Bhaumik Bhatt wrote:
> MHI host can fail early if device is in a bad state by attempting
> to assert device wake and holding the runtime PM vote before
> sending a channel update command instead of performing a wake
> toggle and waiting for a timeout if the send were to fail. This
> can help improve the design and enable shorter wait periods for
> device to respond as votes are already held.
> 
> Signed-off-by: Bhaumik Bhatt <bbhatt@...eaurora.org>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

Thanks,
Mani

> ---
>  drivers/bus/mhi/core/main.c | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> index 94fdbf7..989a2a8 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -1278,16 +1278,18 @@ static int mhi_update_channel_state(struct mhi_controller *mhi_cntrl,
>  		return -EINVAL;
>  	}
>  
> -	mhi_cntrl->wake_toggle(mhi_cntrl);
> +	/* bring host and device out of suspended states */
> +	ret = mhi_device_get_sync(mhi_cntrl->mhi_dev);
> +	if (ret)
> +		return ret;
>  	mhi_cntrl->runtime_get(mhi_cntrl);
> -	mhi_cntrl->runtime_put(mhi_cntrl);
>  
>  	reinit_completion(&mhi_chan->completion);
>  	ret = mhi_send_cmd(mhi_cntrl, mhi_chan, cmd);
>  	if (ret) {
>  		dev_err(dev, "%d: Failed to send %s channel command\n",
>  			mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
> -		return ret;
> +		goto exit_channel_update;
>  	}
>  
>  	ret = wait_for_completion_timeout(&mhi_chan->completion,
> @@ -1296,9 +1298,12 @@ static int mhi_update_channel_state(struct mhi_controller *mhi_cntrl,
>  		dev_err(dev,
>  			"%d: Failed to receive %s channel command completion\n",
>  			mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
> -		return -EIO;
> +		ret = -EIO;
> +		goto exit_channel_update;
>  	}
>  
> +	ret = 0;
> +
>  	if (to_state != MHI_CH_STATE_TYPE_RESET) {
>  		write_lock_irq(&mhi_chan->lock);
>  		mhi_chan->ch_state = (to_state == MHI_CH_STATE_TYPE_START) ?
> @@ -1309,7 +1314,11 @@ static int mhi_update_channel_state(struct mhi_controller *mhi_cntrl,
>  	dev_dbg(dev, "%d: Channel state change to %s successful\n",
>  		mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
>  
> -	return 0;
> +exit_channel_update:
> +	mhi_cntrl->runtime_put(mhi_cntrl);
> +	mhi_device_put(mhi_cntrl->mhi_dev);
> +
> +	return ret;
>  }
>  
>  static void __mhi_unprepare_channel(struct mhi_controller *mhi_cntrl,
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>