[PATCH v2 1/4] memory: mvebu-devbus: fix the conversion of the bus width

[jason@lakedaemon.net (Jason Cooper)]

Thomas,

On Mon, Apr 14, 2014 at 05:29:18PM +0200, Thomas Petazzoni wrote:
> According to the Armada 370 and Armada XP datasheets, the part of the
> Device Bus register that configure the bus width should contain 0 for
> a 8 bits bus width, and 1 for a 16 bits bus width (other values are
> unsupported/reserved).
> 
> However, the current conversion done in the driver to convert from a
> bus width in bits to the value expected by the register leads to
> setting the register to 1 for a 8 bits bus, and 2 for a 16 bits bus.
> 
> This mistake was compensated by a mistake in the existing Device Tree
> files for Armada 370/XP platforms: they were declaring a 8 bits bus
> width, while the hardware in fact uses a 16 bits bus width.
> 
> This commit fixes that by adjusting the conversion logic.
> 
> This patch fixes a bug that was introduced in
> 3edad321b1bd2e6c8b5f38146c115c8982438f06 ('drivers: memory: Introduce
> Marvell EBU Device Bus driver'), which was merged in v3.11.
> 
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> Cc: stable at vger.kernel.org
> ---
>  drivers/memory/mvebu-devbus.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/memory/mvebu-devbus.c b/drivers/memory/mvebu-devbus.c
> index 110c036..b59a17f 100644
> --- a/drivers/memory/mvebu-devbus.c
> +++ b/drivers/memory/mvebu-devbus.c
> @@ -108,8 +108,19 @@ static int devbus_set_timing_params(struct devbus *devbus,
>  			node->full_name);
>  		return err;
>  	}
> -	/* Convert bit width to byte width */
> -	r.bus_width /= 8;
> +
> +	/*
> +	 * The bus width is encoded into the register as 0 for 8 bits,
> +	 * and 1 for 16 bits, so we do the necessary conversion here.
> +	 */
> +	if (r.bus_width == 8)
> +		r.bus_width = 0;
> +	else if (r.bus_width == 16)
> +		r.bus_width = 1;
> +	else {
> +		dev_err(devbus->dev, "invalid bus width %d\n", r.bus_width);
> +		return -EINVAL;
> +	}

This looks strikingly similar to patch 4/29 of your own orion5x DT
conversion series, but with completely different code...  Which one
would you prefer I take?

thx,

Jason.