linux-kernel - Re: [PATCH 2/3] MTD: spi-nor: check for short writes in spi_nor

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Date:	Wed, 20 May 2015 16:38:35 -0700
From:	Brian Norris <computersforpeace@...il.com>
To:	Michal Suchanek <hramrach@...il.com>
Cc:	linux-sunxi@...glegroups.com, Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Marek Vasut <marex@...x.de>,
	Huang Shijie <b32955@...escale.com>,
	Rafał Miłecki <zajec5@...il.com>,
	Ben Hutchings <ben@...adent.org.uk>,
	Alison Chaiken <alison_chaiken@...tor.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Bean Huo 霍斌斌 (beanhuo) 
	<beanhuo@...ron.com>, "grmoore@...era.com" <grmoore@...era.com>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mtd@...ts.infradead.org, linux-spi@...r.kernel.org,
	Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH 2/3] MTD: spi-nor: check for short writes in
 spi_nor_write.

+ linux-spi, Mark

On Thu, Apr 30, 2015 at 03:38:50PM +0200, Michal Suchanek wrote:
> My SPI controller driver does not support DMA so writes are truncated to
> FIFO size.

Which SPI master driver?

> Check the amount of data actually written by the driver.

I'm not sure if we should just reactively use the retlen, or if we
should be communicating such a limitation via the SPI API. Thoughts?

Brian

> Signed-off-by: Michal Suchanek <hramrach@...il.com>
> ---
>  drivers/mtd/spi-nor/spi-nor.c | 42 +++++++++++++++++-------------------------
>  1 file changed, 17 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index 14a5d23..75904b5 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -807,7 +807,7 @@ static int spi_nor_write(struct mtd_info *mtd, loff_t to, size_t len,
>  	size_t *retlen, const u_char *buf)
>  {
>  	struct spi_nor *nor = mtd_to_spi_nor(mtd);
> -	u32 page_offset, page_size, i;
> +	u32 page_offset, page_remainder, page_size, i;
>  	int ret;
>  
>  	dev_dbg(nor->dev, "to 0x%08x, len %zd\n", (u32)to, len);
> @@ -816,36 +816,28 @@ static int spi_nor_write(struct mtd_info *mtd, loff_t to, size_t len,
>  	if (ret)
>  		return ret;
>  
> -	write_enable(nor);
> -
> -	page_offset = to & (nor->page_size - 1);
> -
> -	/* do all the bytes fit onto one page? */
> -	if (page_offset + len <= nor->page_size) {
> -		nor->write(nor, to, len, retlen, buf);
> -	} else {
> -		/* the size of data remaining on the first page */
> -		page_size = nor->page_size - page_offset;
> -		nor->write(nor, to, page_size, retlen, buf);
> +	/* write everything in nor->page_size chunks */
> +	/* check the size of data actually written */
> +	for (i = 0; i < len; i += *retlen) {
> +		page_size = len - i;
> +		page_offset = (to + i) & (nor->page_size - 1);
> +		page_remainder = nor->page_size - page_offset;
> +		if (page_size > nor->page_size)
> +			page_size = nor->page_size;
> +		if (page_remainder && (page_size > page_remainder))
> +			page_size = page_remainder;
>  
> -		/* write everything in nor->page_size chunks */
> -		for (i = page_size; i < len; i += page_size) {
> -			page_size = len - i;
> -			if (page_size > nor->page_size)
> -				page_size = nor->page_size;
> -
> -			ret = spi_nor_wait_till_ready(nor);
> -			if (ret)
> -				goto write_err;
> +		write_enable(nor);
>  
> -			write_enable(nor);
> +		nor->write(nor, to + i, page_size, retlen, buf + i);
>  
> -			nor->write(nor, to + i, page_size, retlen, buf + i);
> -		}
> +		ret = spi_nor_wait_till_ready(nor);
> +		if (ret)
> +			goto write_err;
>  	}
>  
> -	ret = spi_nor_wait_till_ready(nor);
>  write_err:
> +	*retlen = i;
>  	spi_nor_unlock_and_unprep(nor, SPI_NOR_OPS_WRITE);
>  	return ret;
>  }
--
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