linux-kernel - Re: [PATCH v2 03/18] fpga: dfl: fme: align PR buffer size per PR datawidth

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Message-ID: <20190507172732.GB26690@archbox>
Date:   Tue, 7 May 2019 10:27:32 -0700
From:   Moritz Fischer <mdf@...nel.org>
To:     Wu Hao <hao.wu@...el.com>
Cc:     atull@...nel.org, mdf@...nel.org, linux-fpga@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        Xu Yilun <yilun.xu@...el.com>
Subject: Re: [PATCH v2 03/18] fpga: dfl: fme: align PR buffer size per PR
 datawidth

On Mon, Apr 29, 2019 at 04:55:36PM +0800, Wu Hao wrote:
> Current driver checks if input bitstream file size is aligned or
> not per PR data width (default 32bits). It requires one additional
> step for end user when they generate the bitstream file, padding
> extra zeros to bitstream file to align its size per PR data width,
> but they don't have to as hardware will drop extra padding bytes
> automatically.
> 
> In order to simplify the user steps, this patch aligns PR buffer
> size per PR data width in driver, to allow user to pass unaligned
> size bitstream files to driver.
> 
> Signed-off-by: Xu Yilun <yilun.xu@...el.com>
> Signed-off-by: Wu Hao <hao.wu@...el.com>
> Acked-by: Alan Tull <atull@...nel.org>
Acked-by: Moritz Fischer <mdf@...nel.org>
> ---
>  drivers/fpga/dfl-fme-pr.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/fpga/dfl-fme-pr.c b/drivers/fpga/dfl-fme-pr.c
> index 6ec0f09..3c71dc3 100644
> --- a/drivers/fpga/dfl-fme-pr.c
> +++ b/drivers/fpga/dfl-fme-pr.c
> @@ -74,6 +74,7 @@ static int fme_pr(struct platform_device *pdev, unsigned long arg)
>  	struct dfl_fme *fme;
>  	unsigned long minsz;
>  	void *buf = NULL;
> +	size_t length;
>  	int ret = 0;
>  	u64 v;
>  
> @@ -85,9 +86,6 @@ static int fme_pr(struct platform_device *pdev, unsigned long arg)
>  	if (port_pr.argsz < minsz || port_pr.flags)
>  		return -EINVAL;
>  
> -	if (!IS_ALIGNED(port_pr.buffer_size, 4))
> -		return -EINVAL;
> -
>  	/* get fme header region */
>  	fme_hdr = dfl_get_feature_ioaddr_by_id(&pdev->dev,
>  					       FME_FEATURE_ID_HEADER);
> @@ -103,7 +101,13 @@ static int fme_pr(struct platform_device *pdev, unsigned long arg)
>  		       port_pr.buffer_size))
>  		return -EFAULT;
>  
> -	buf = vmalloc(port_pr.buffer_size);
> +	/*
> +	 * align PR buffer per PR bandwidth, as HW ignores the extra padding
> +	 * data automatically.
> +	 */
> +	length = ALIGN(port_pr.buffer_size, 4);
> +
> +	buf = vmalloc(length);
>  	if (!buf)
>  		return -ENOMEM;
>  
> @@ -140,7 +144,7 @@ static int fme_pr(struct platform_device *pdev, unsigned long arg)
>  	fpga_image_info_free(region->info);
>  
>  	info->buf = buf;
> -	info->count = port_pr.buffer_size;
> +	info->count = length;
>  	info->region_id = port_pr.port_id;
>  	region->info = info;
>  
> -- 
> 1.8.3.1
>