linux-kernel - Re: [PATCH] nvmem: qfprom: Specify LE device endianness

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Date:	Sat, 21 Nov 2015 13:48:01 +0000
From:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:	Stephen Boyd <sboyd@...eaurora.org>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>
CC:	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Rajendra Nayak <rnayak@...eaurora.org>,
	Kevin Hilman <khilman@...aro.org>,
	Tyler Baker <tyler.baker@...aro.org>,
	Simon Arlott <simon@...e.lp0.eu>,
	Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH] nvmem: qfprom: Specify LE device endianness

Hi Stephen,

Thanks for the fix.

I will send it to Greg for next rc.

--srini
On 20/11/15 23:37, Stephen Boyd wrote:
> The qfprom is a little endian device, but so far we've been
> relying on the regmap mmio bus handling this for us without
> explicitly stating that fact. After commit 4a98da2164cf
> (regmap-mmio: Use native endianness for read/write, 2015-10-29),
> the regmap mmio bus will read/write with the __raw_*() IO
> accessors, instead of using the readl/writel() APIs that do
> proper byte swapping for little endian devices.
>
> So if we're running on a big endian processor and haven't
> specified the endianness explicitly in the regmap config or in
> DT, we're going to switch from doing little endian byte swapping
> to big endian accesses without byte swapping, leading to some
> confusing results. Specify the endianness explicitly so that the
> regmap core properly byte swaps the accesses for us.
>
> Cc: Rajendra Nayak <rnayak@...eaurora.org>
> Cc: Kevin Hilman <khilman@...aro.org>
> Cc: Tyler Baker <tyler.baker@...aro.org>
> Cc: Simon Arlott <simon@...e.lp0.eu>
> Cc: Mark Brown <broonie@...nel.org>
> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
> ---
>   drivers/nvmem/qfprom.c | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/drivers/nvmem/qfprom.c b/drivers/nvmem/qfprom.c
> index afb67e7eeee4..3829e5fbf8c3 100644
> --- a/drivers/nvmem/qfprom.c
> +++ b/drivers/nvmem/qfprom.c
> @@ -21,6 +21,7 @@ static struct regmap_config qfprom_regmap_config = {
>   	.reg_bits = 32,
>   	.val_bits = 8,
>   	.reg_stride = 1,
> +	.val_format_endian = REGMAP_ENDIAN_LITTLE,
>   };
>
>   static struct nvmem_config econfig = {
>
--
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