[PATCH] mtd: spi-nor: Only set Micron quad-read mode when controller in 4-lane TX mode

[Graham Moore]

On 06/30/2015 06:17 AM, Mike Looijmans wrote:
> Micron QUAD mode expects command, address and data on 4 lanes instead of just
> one for command (extended SPI mode). This requires the controller to be in a
> special mode, so check first if the controller could be in that mode. If a
> controller does not have the SPI_TX_QUAD mode set, this setting has no chance
> of being valid at all, so don't try to enable it then, and just keep using
> the extended SPI mode.
>
> Tested on a Zynq 7000 with a n25q256a flash chip, this failed to function
> because of the introduction of:
> "driver:mtd:spi-nor: Add quad I/O support for Micron spi nor"
> This commit sets QUAD mode for most Micron chips without asking the controller
> whether it's possible to do so, and without telling the controller that a
> different mode is required, so it couldn't work.
>
> Signed-off-by: Mike Looijmans <mike.looijmans at topic.nl>
> ---
>   drivers/mtd/spi-nor/spi-nor.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index e8f6131..10ba94f 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -1398,6 +1398,8 @@ static int set_quad_mode(struct spi_nor *nor, struct flash_info *info)
>   		}
>   		return status;
>   	case CFI_MFR_ST:
> +		if (!(nor->spi->mode & SPI_TX_QUAD))
> +			return 0;

This is a great idea, but what codebase are you working from?  My l2-mtd 
tree doesn't have a 'spi' member of spi_nor, and this case statement is 
around line 977, not 1398.

>   		status = micron_quad_enable(nor);
>   		if (status) {
>   			dev_err(nor->dev, "Micron quad-read not enabled\n");
>

Regards,
Graham