linux-kernel - Re: [PATCH v2 6/6] bus: mhi: Improve documentation on channel transfer setup APIs

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Date:   Mon, 16 Nov 2020 18:20:45 +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, loic.poulain@...aro.org,
        kvalo@...eaurora.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 6/6] bus: mhi: Improve documentation on channel
 transfer setup APIs

On Wed, Nov 11, 2020 at 11:21:13AM -0800, Bhaumik Bhatt wrote:
> The mhi_prepare_for_transfer() and mhi_unprepare_from_transfer()
> APIs could use better explanation, especially with the addition
> of two new APIs to start and stop the transfers on channels. Add
> better set of information for those APIs to avoid confusion going
> forward.
> 
> Signed-off-by: Bhaumik Bhatt <bbhatt@...eaurora.org>
> ---
>  include/linux/mhi.h | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/mhi.h b/include/linux/mhi.h
> index aee8494..ee9537f 100644
> --- a/include/linux/mhi.h
> +++ b/include/linux/mhi.h
> @@ -690,13 +690,27 @@ int mhi_device_get_sync(struct mhi_device *mhi_dev);
>  void mhi_device_put(struct mhi_device *mhi_dev);
>  
>  /**
> - * mhi_prepare_for_transfer - Setup channel for data transfer
> + * mhi_prepare_for_transfer - Setup UL and DL channels for data transfer.
> + *                            Allocate and initialize the channel context and
> + *                            also issue the START channel command to both
> + *                            channels. Channels can be started only if both
> + *                            host and device execution environments match and
> + *                            channels are in a DISABLED state.

It'd be good if you can add a note about how this API differs from
mhi_start_transfer() API. The content says the difference but an explicit
comparision would be good.

Thanks,
Mani

>   * @mhi_dev: Device associated with the channels
>   */
>  int mhi_prepare_for_transfer(struct mhi_device *mhi_dev);
>  
>  /**
> - * mhi_unprepare_from_transfer - Unprepare the channels
> + * mhi_unprepare_from_transfer - Reset UL and DL channels for data transfer.
> + *                               Issue the RESET channel command and let the
> + *                               device clean-up the context so no incoming
> + *                               transfers are seen on the host. Free memory
> + *                               associated with the context on host. If device
> + *                               is unresponsive, only perform a host side
> + *                               clean-up. Channels can be reset only if both
> + *                               host and device execution environments match
> + *                               and channels are in an ENABLED, STOPPED or
> + *                               SUSPENDED state.
>   * @mhi_dev: Device associated with the channels
>   */
>  void mhi_unprepare_from_transfer(struct mhi_device *mhi_dev);
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>