linux-kernel - Re: [PATCH v3 1/3] bus: mhi: core: Introduce internal register poll helper function

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Message-ID: <b53a5cf8-aa25-0e89-b83f-57ec32fa7075@codeaurora.org>
Date:   Wed, 10 Mar 2021 11:57:19 -0700
From:   Jeffrey Hugo <jhugo@...eaurora.org>
To:     Bhaumik Bhatt <bbhatt@...eaurora.org>,
        manivannan.sadhasivam@...aro.org
Cc:     linux-arm-msm@...r.kernel.org, hemantk@...eaurora.org,
        linux-kernel@...r.kernel.org, loic.poulain@...aro.org,
        carl.yin@...ctel.com, naveen.kumar@...ctel.com
Subject: Re: [PATCH v3 1/3] bus: mhi: core: Introduce internal register poll
 helper function

On 2/23/2021 8:44 PM, Bhaumik Bhatt wrote:
> Introduce helper function to allow MHI core driver to poll for
> a value in a register field. This helps reach a common path to
> read and poll register values along with a retry time interval.
> 
> Signed-off-by: Bhaumik Bhatt <bbhatt@...eaurora.org>
> ---
>   drivers/bus/mhi/core/internal.h |  3 +++
>   drivers/bus/mhi/core/main.c     | 23 +++++++++++++++++++++++
>   2 files changed, 26 insertions(+)
> 
> diff --git a/drivers/bus/mhi/core/internal.h b/drivers/bus/mhi/core/internal.h
> index 6f80ec3..005286b 100644
> --- a/drivers/bus/mhi/core/internal.h
> +++ b/drivers/bus/mhi/core/internal.h
> @@ -643,6 +643,9 @@ int __must_check mhi_read_reg(struct mhi_controller *mhi_cntrl,
>   int __must_check mhi_read_reg_field(struct mhi_controller *mhi_cntrl,
>   				    void __iomem *base, u32 offset, u32 mask,
>   				    u32 shift, u32 *out);
> +int __must_check mhi_poll_reg_field(struct mhi_controller *mhi_cntrl,
> +				    void __iomem *base, u32 offset, u32 mask,
> +				    u32 shift, u32 val, u32 delayus);
>   void mhi_write_reg(struct mhi_controller *mhi_cntrl, void __iomem *base,
>   		   u32 offset, u32 val);
>   void mhi_write_reg_field(struct mhi_controller *mhi_cntrl, void __iomem *base,
> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> index 4e0131b..249ae26 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -4,6 +4,7 @@
>    *
>    */
>   
> +#include <linux/delay.h>
>   #include <linux/device.h>
>   #include <linux/dma-direction.h>
>   #include <linux/dma-mapping.h>
> @@ -37,6 +38,28 @@ int __must_check mhi_read_reg_field(struct mhi_controller *mhi_cntrl,
>   	return 0;
>   }
>   
> +int __must_check mhi_poll_reg_field(struct mhi_controller *mhi_cntrl,
> +				    void __iomem *base, u32 offset,
> +				    u32 mask, u32 shift, u32 val, u32 delayus)
> +{
> +	int ret = -ENOENT;
> +	u32 out, retry = (mhi_cntrl->timeout_ms * 1000) / delayus;
> +
> +	while (retry--) {
> +		ret = mhi_read_reg_field(mhi_cntrl, base, offset, mask, shift,
> +					 &out);
> +		if (ret)
> +			return -EIO;

I generally dislike recoding return codes.  Do you believe it adds value 
here?  I'm concerned that if I'm debugging an error, I'll get EIO, which 
I trace to here, but then I don't know what the actual error from 
mhi_read_reg_field() was.

> +
> +		if (out == val)
> +			return 0;
> +
> +		udelay(delayus);
> +	}
> +
> +	return ret;
> +}
> +
>   void mhi_write_reg(struct mhi_controller *mhi_cntrl, void __iomem *base,
>   		   u32 offset, u32 val)
>   {
> 


-- 
Jeffrey Hugo
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.