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SubjectRe: [PATCH] gpio: pca953x: Don't flip bits on PCA957x GPIO expanders when probing them.
From
On Sat, Aug 3, 2013 at 5:24 AM, Graeme Smecher
<gsmecher@threespeedlogic.com> wrote:
> The pca957x driver supports a handful of I2C GPIO expanders from NXP, Maxim,
> and TI. For the PCA9574 and PCA9575 devices only, the driver resets the GPIO
> level and direction in the pca957x_probe function. This seems like the wrong
> thing to do, since it can cause hardware bit twiddles during warm reboots when
> the chip state and reset values don't match.
>
> This kind of initialization is best left upstream (in a bootloader) or
> downstream (in userspace). It's also an inconsistency across devices supported
> by this driver.
>
> Signed-off-by: Graeme Smecher <gsmecher@threespeedlogic.com>
> Cc: Grant Likely <grant.likely@linaro.org>
> Cc: Haojian Zhuang <haojian.zhuang@marvell.com>
> ---
> drivers/gpio/gpio-pca953x.c | 11 -----------
> 1 file changed, 11 deletions(-)
>
> diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
> index 426c51d..47c08d8 100644
> --- a/drivers/gpio/gpio-pca953x.c
> +++ b/drivers/gpio/gpio-pca953x.c
> @@ -683,17 +683,6 @@ static int device_pca957x_init(struct pca953x_chip *chip, u32 invert)
> int ret;
> u8 val[MAX_BANK];
>
> - /* Let every port in proper state, that could save power */
> - memset(val, 0, NBANK(chip));
> - pca953x_write_regs(chip, PCA957X_PUPD, val);
> - memset(val, 0xFF, NBANK(chip));
> - pca953x_write_regs(chip, PCA957X_CFG, val);
> - memset(val, 0, NBANK(chip));
> - pca953x_write_regs(chip, PCA957X_OUT, val);
> -
> - ret = pca953x_read_regs(chip, PCA957X_IN, val);
> - if (ret)
> - goto out;
> ret = pca953x_read_regs(chip, PCA957X_OUT, chip->reg_output);
> if (ret)
> goto out;
> --
> 1.7.10.4
>

Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com>


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