linux-kernel - Re: [PATCH v2 3/5] fpga manager: xilinx-spi: rework write

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Date:   Thu, 27 Aug 2020 11:59:19 -0700
From:   Tom Rix <trix@...hat.com>
To:     Luca Ceresoli <luca@...aceresoli.net>, linux-fpga@...r.kernel.org
Cc:     Moritz Fischer <mdf@...nel.org>,
        Michal Simek <michal.simek@...inx.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Anatolij Gustschin <agust@...x.de>
Subject: Re: [PATCH v2 3/5] fpga manager: xilinx-spi: rework write_complete
 loop implementation


On 8/27/20 7:32 AM, Luca Ceresoli wrote:
> In preparation to add error checking for gpiod_get_value(), rework
> the loop to avoid the duplication of these lines:
>
> 	if (gpiod_get_value(conf->done))
> 		return xilinx_spi_apply_cclk_cycles(conf);
>
> There is little advantage in this rework with current code. However
> error checking will expand these two lines to five, making code
> duplication more annoying.
>
> Signed-off-by: Luca Ceresoli <luca@...aceresoli.net>
>
> ---
>
> This patch is new in v2
> ---
>  drivers/fpga/xilinx-spi.c | 15 ++++++---------
>  1 file changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/fpga/xilinx-spi.c b/drivers/fpga/xilinx-spi.c
> index 01f494172379..cfc933d70f52 100644
> --- a/drivers/fpga/xilinx-spi.c
> +++ b/drivers/fpga/xilinx-spi.c
> @@ -151,22 +151,19 @@ static int xilinx_spi_write_complete(struct fpga_manager *mgr,
>  				     struct fpga_image_info *info)
>  {
>  	struct xilinx_spi_conf *conf = mgr->priv;
> -	unsigned long timeout;
> +	unsigned long timeout = jiffies + usecs_to_jiffies(info->config_complete_timeout_us);
>  	int ret;
>  
> -	if (gpiod_get_value(conf->done))
> -		return xilinx_spi_apply_cclk_cycles(conf);
> -
> -	timeout = jiffies + usecs_to_jiffies(info->config_complete_timeout_us);
> +	while (true) {
> +		if (gpiod_get_value(conf->done))
> +			return xilinx_spi_apply_cclk_cycles(conf);
>  
> -	while (time_before(jiffies, timeout)) {
> +		if (time_after(jiffies, timeout))
> +			break;
>  
>  		ret = xilinx_spi_apply_cclk_cycles(conf);
>  		if (ret)
>  			return ret;
> -
> -		if (gpiod_get_value(conf->done))
> -			return xilinx_spi_apply_cclk_cycles(conf);
>  	} 

Do you need another

	if (gpiod_get_value(conf->done))
		return xilinx_spi_apply_cclk_cycles(conf);

here to cover the chance of sleeping in the loop ?

Tom

>  
>  	dev_err(&mgr->dev, "Timeout after config data transfer\n");