linux-kernel - Re: [PATCH v4 2/3] bus: mhi: host: Add a new API for getting channel doorbell address

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Message-ID: <20240425135506.GF3449@thinkpad>
Date: Thu, 25 Apr 2024 19:25:06 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Qiang Yu <quic_qianyu@...cinc.com>
Cc: quic_jhugo@...cinc.com, mhi@...ts.linux.dev,
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
	quic_cang@...cinc.com, quic_mrana@...cinc.com
Subject: Re: [PATCH v4 2/3] bus: mhi: host: Add a new API for getting channel
 doorbell address

On Tue, Apr 23, 2024 at 06:33:36PM +0800, Qiang Yu wrote:
> Some controllers may want to know the address of a certain doorbell. Hence
> add a new API where we read CHDBOFF register to get the base address of
> doorbell, so that the controller can calculate the address of the doorbell
> it wants by adding additional offset.
> 
> Signed-off-by: Qiang Yu <quic_qianyu@...cinc.com>

One nitpick below. But I'll fix it.

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

> ---
>  drivers/bus/mhi/host/init.c |  6 ++----
>  drivers/bus/mhi/host/main.c | 16 ++++++++++++++++
>  include/linux/mhi.h         |  6 ++++++
>  3 files changed, 24 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
> index 7104c18..6e0fa79 100644
> --- a/drivers/bus/mhi/host/init.c
> +++ b/drivers/bus/mhi/host/init.c
> @@ -541,11 +541,9 @@ int mhi_init_mmio(struct mhi_controller *mhi_cntrl)
>  	dev_dbg(dev, "Initializing MHI registers\n");
>  
>  	/* Read channel db offset */
> -	ret = mhi_read_reg(mhi_cntrl, base, CHDBOFF, &val);
> -	if (ret) {
> -		dev_err(dev, "Unable to read CHDBOFF register\n");
> +	ret = mhi_get_channel_doorbell_offset(mhi_cntrl, &val);
> +	if (ret)
>  		return -EIO;

	return ret;

- Mani

> -	}
>  
>  	if (val >= mhi_cntrl->reg_len - (8 * MHI_DEV_WAKE_DB)) {
>  		dev_err(dev, "CHDB offset: 0x%x is out of range: 0x%zx\n",
> diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
> index 15d657a..4de7567 100644
> --- a/drivers/bus/mhi/host/main.c
> +++ b/drivers/bus/mhi/host/main.c
> @@ -1691,3 +1691,19 @@ void mhi_unprepare_from_transfer(struct mhi_device *mhi_dev)
>  	}
>  }
>  EXPORT_SYMBOL_GPL(mhi_unprepare_from_transfer);
> +
> +int mhi_get_channel_doorbell_offset(struct mhi_controller *mhi_cntrl, u32 *chdb_offset)
> +{
> +	struct device *dev = &mhi_cntrl->mhi_dev->dev;
> +	void __iomem *base = mhi_cntrl->regs;
> +	int ret;
> +
> +	ret = mhi_read_reg(mhi_cntrl, base, CHDBOFF, chdb_offset);
> +	if (ret) {
> +		dev_err(dev, "Unable to read CHDBOFF register\n");
> +		return -EIO;
> +	}
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(mhi_get_channel_doorbell_offset);
> diff --git a/include/linux/mhi.h b/include/linux/mhi.h
> index d968e1a..cb3b676 100644
> --- a/include/linux/mhi.h
> +++ b/include/linux/mhi.h
> @@ -816,4 +816,10 @@ int mhi_queue_skb(struct mhi_device *mhi_dev, enum dma_data_direction dir,
>   */
>  bool mhi_queue_is_full(struct mhi_device *mhi_dev, enum dma_data_direction dir);
>  
> +/**
> + * mhi_get_channel_doorbell_offset - Get the channel doorbell offset
> + * @mhi_cntrl: MHI controller
> + * @chdb_offset: Channel doorbell offset
> + */
> +int mhi_get_channel_doorbell_offset(struct mhi_controller *mhi_cntrl, u32 *chdb_offset);
>  #endif /* _MHI_H_ */
> -- 
> 2.7.4
> 
> 

-- 
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