linux-kernel - Re: [PATCH v5] mtd: spi-nor: Add support for S3AN spi-nor devices

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Date:   Tue, 20 Sep 2016 18:25:39 +0200
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
Cc:     Cyrille Pitchen <cyrille.pitchen@...el.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Javier Martinez Canillas <javier@....samsung.com>,
        Stephen Warren <swarren@...dia.com>,
        Jagan Teki <jteki@...nedev.com>, Vignesh R <vigneshr@...com>,
        Marek Vasut <marex@...x.de>,
        Ezequiel García 
        <ezequiel@...guardiasur.com.ar>,
        Rafał Miłecki <zajec5@...il.com>,
        Furquan Shaikh <furquan@...gle.com>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] mtd: spi-nor: Add support for S3AN spi-nor devices

On Fri, 16 Sep 2016 21:33:52 +0200
Ricardo Ribalda Delgado <ricardo.ribalda@...il.com> wrote:

> Xilinx Spartan-3AN FPGAs contain an In-System Flash where they keep
> their configuration data and (optionally) some user data.
> 
> The protocol of this flash follows most of the spi-nor standard. With
> the following differences:
> 
> - Page size might not be a power of two.
> - The address calculation (default addressing mode).
> - The spi nor commands used.
> 
> Protocol is described on Xilinx User Guide UG333
> 
> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
> ---
> v5:
> -Rebase on top of l2-mtd/master
> Suggested by: Cyrille Pitchen <cyrille.pitchen@...el.com>:
> -Fix to+1 bug
> -Move all address conversions to spi-nor
> -Replace pr_dev with dev_err
> 
> v4:
> -Rebase on top of l2-mtd/master
> 
> v3:
> -Rebase on top of mtd-next
> -Rename ADDR_NATIVE to ADDR_DEFAULT to follow UG333 naming
> -Fix bug on probe
> 
> v2: Suggested by Brian Norris <computersforpeace@...il.com>
> 
> -Remove inline qualifier
> -Improve documentation of Default Addressing Mode
> -Convert function callbacks into SNOR_F_
> -Fix missmatch braces
> -Improve documentation of SPI_S3AN flag
>  drivers/mtd/spi-nor/spi-nor.c | 122 ++++++++++++++++++++++++++++++++++++++++--
>  include/linux/mtd/spi-nor.h   |  12 +++++
>  2 files changed, 129 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index d0fc165d7d66..94c5fd870058 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c

[...]

>  /*
> + * This code converts an address to the Default Address Mode, that has non
> + * power of two page sizes. We must support this mode because it is the default
> + * mode supported by Xilinx tools, it can access the whole flash area and
> + * changing over to the Power-of-two mode is irreversible and corrupts the
> + * original data.
> + */
> +static loff_t spi_nor_s3an_addr_convert(struct spi_nor *nor, unsigned int addr)
> +{
> +	unsigned int offset;
> +
> +	offset = (nor->page_size == 264) ? (addr % 264) : (addr % 528);
> +
> +	return ((addr - offset) << 1) | offset;
> +}

[...]

>  
> @@ -1049,7 +1111,12 @@ static int spi_nor_read(struct mtd_info *mtd, loff_t from, size_t len,
>  		return ret;
>  
>  	while (len) {
> -		ret = nor->read(nor, from, len, buf);
> +		loff_t addr = from;
> +
> +		if (nor->flags & SNOR_F_S3AN_ADDR_DEFAULT)
> +			addr = spi_nor_s3an_addr_convert(nor, addr);

Don't know if that's important since NOR flashes are unlikely to be
larger than 4GB, but you're casting a loff_t (unsigned long long) type
to an unsigned int (spi_nor_s3an_addr_convert() is taking an unsigned
int).