linux-kernel - Re: [PATCH v2] fpga: altera-cvp: allow interrupt to continue next time

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Date:   Fri, 3 Jun 2022 19:00:46 +0800
From:   Xu Yilun <yilun.xu@...el.com>
To:     tien.sung.ang@...el.com
Cc:     hao.wu@...el.com, linux-fpga@...r.kernel.org,
        linux-kernel@...r.kernel.org, mdf@...nel.org, trix@...hat.com,
        dinh.nguyen@...el.com
Subject: Re: [PATCH v2] fpga: altera-cvp: allow interrupt to continue next
 time

On Wed, Jun 01, 2022 at 09:40:27AM +0800, tien.sung.ang@...el.com wrote:
> From: Dinh Nguyen <dinh.nguyen@...el.com>
> 
> The main objective of this change is to perform error handling
> if the CvP firmware becomes unresponsive. The error_path flow
> resets the CvP mode and HIP_CLK_SEL bit.
> 
> CFG_READY signal/bit may time-out due to firmware not responding
> within the given time-out. This time varies due to numerous
> factors like size of bitstream and others.
> This time-out error may or may not impact the result of the CvP
> previous transactions. The CvP driver shall then, respond with
> EAGAIN instead Time out error.
> 
> Signed-off-by: Dinh Nguyen <dinh.nguyen@...el.com>
> Signed-off-by: Ang Tien Sung <tien.sung.ang@...el.com>
> ---
> 
> changelog v2:
> * Amend the commit message
> 
> ---
>  drivers/fpga/altera-cvp.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/fpga/altera-cvp.c b/drivers/fpga/altera-cvp.c
> index 4ffb9da537d8..d74ff63c61e8 100644
> --- a/drivers/fpga/altera-cvp.c
> +++ b/drivers/fpga/altera-cvp.c
> @@ -309,10 +309,22 @@ static int altera_cvp_teardown(struct fpga_manager *mgr,
>  	/* STEP 15 - poll CVP_CONFIG_READY bit for 0 with 10us timeout */
>  	ret = altera_cvp_wait_status(conf, VSE_CVP_STATUS_CFG_RDY, 0,
>  				     conf->priv->poll_time_us);
> -	if (ret)
> +	if (ret) {
>  		dev_err(&mgr->dev, "CFG_RDY == 0 timeout\n");
> +		goto error_path;

I assume the error handling is specific to CFG_RDY timeout, is it? Then it
could be embedded in this code block.

And also the -EAGAIN ret, please only return it in this code block.

Usually the goto error path is for common fail out.

> +	}
>  
>  	return ret;
> +
> +error_path:
> +	/* reset CVP_MODE and HIP_CLK_SEL bit */
> +	altera_read_config_dword(conf, VSE_CVP_MODE_CTRL, &val);
> +	val &= ~VSE_CVP_MODE_CTRL_HIP_CLK_SEL;
> +	val &= ~VSE_CVP_MODE_CTRL_CVP_MODE;
> +	altera_write_config_dword(conf, VSE_CVP_MODE_CTRL, val);
> +
> +	return -EAGAIN;

Please still specify the reason for -EAGAIN rather than timeout.

Thanks,
Yilun

> +
>  }
>  
>  static int altera_cvp_write_init(struct fpga_manager *mgr,
> -- 
> 2.25.1