Re: [PATCH v3] mtd: spi-nor: Add support for Cypress cy15x104q

[Sascha Hauer <s.hauer@pengutronix.de>]

On Fri, Apr 24, 2020 at 08:56:26AM +0200, Sascha Hauer wrote:
> The Cypress cy15b104q and cy15v104q are 4Mbit serial SPI F-RAM devices.
> Add support for them to the spi-nor driver.
> 
> The actual Device ID of this chip is 7f 7f 7f 7f 7f 7f c2 2c 04. That is
> six times the continuation code 7f followed by c2 for Ramtron.
> Unfortunately the chip sends the Device ID in reversed order, so the
> continuation code is not at the beginning, but instead at the end. Even
> more unfortunate is that when reading further the chip sends more 7f
> codes which means we are not even able to count the continuation codes.
> We can only hope that this reversed Device ID will never match any other
> devices ID.

Any idea how to continue here? The patch is wrong, I know that, but I
have no idea what to do instead. Should we just skip support for this
chip?

Sascha

> 
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
> 
> Changes since v2:
> - Add explanation of the reversed order of the Device ID to the commit message
> Changes since v1:
> - Instead of specifying 1024 sectors with a sector size of 512 specify
>   512 * 1024 sectos with a sector size of 1. The device has no idea of
>   sectors and is not erasable, so a sector size of 1 seems to better
>   reflect reality.
> 
>  drivers/mtd/spi-nor/spansion.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/mtd/spi-nor/spansion.c b/drivers/mtd/spi-nor/spansion.c
> index 6756202ace4b..3e8ac602e36b 100644
> --- a/drivers/mtd/spi-nor/spansion.c
> +++ b/drivers/mtd/spi-nor/spansion.c
> @@ -70,6 +70,7 @@ static const struct flash_info spansion_parts[] = {
>  	{ "s25fl256l",  INFO(0x016019,      0,  64 * 1024, 512,
>  			     SECT_4K | SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ |
>  			     SPI_NOR_4B_OPCODES) },
> +	{ "cy15x104q",  INFO6(0x042cc2, 0x7f7f7f, 512 * 1024, 1, SPI_NOR_NO_ERASE) },
>  };
>  
>  static void spansion_post_sfdp_fixups(struct spi_nor *nor)
> -- 
> 2.26.1
> 
> 

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