[PATCH v2 1/2] pinctrl: pinctrl-imx: add support for set bits for general purpose registers

[jason77.wang@gmail.com (Hui Wang)]

Dong Aisheng wrote:
> From: Dong Aisheng <dong.aisheng@linaro.org>
>
> The General Purpose Registers (GPR) is used to select operating modes for
> general features in the SoC, usually not related to the IOMUX itself,
> but it does belong to IOMUX controller.
> We simply provide an convient API for driver to call to write/read the general
> purpose register bits if needed.
>
> Signed-off-by: Dong Aisheng <dong.aisheng@linaro.org>
> ---
> ChangeLog v1->v2:
> * add gpr read api
> * change api name a bit to *_write and *_read
> * add -EPROBE_DEFER support
> * define macros for gpr registers for imx6q
> * change driver loadding priority to postcore_init at satisfy clients driver
>   to use imx_pinctrl_gpr_{read | write} APIs at best
> ---
>  drivers/pinctrl/pinctrl-imx.c   |   29 ++++
>  drivers/pinctrl/pinctrl-imx51.c |    2 +-
>  drivers/pinctrl/pinctrl-imx53.c |    2 +-
>  drivers/pinctrl/pinctrl-imx6q.c |    2 +-
>  include/linux/fsl/imx-pinctrl.h |  340 +++++++++++++++++++++++++++++++++++++++
>  5 files changed, 372 insertions(+), 3 deletions(-)
>  create mode 100644 include/linux/fsl/imx-pinctrl.h
>
> diff --git a/drivers/pinctrl/pinctrl-imx.c b/drivers/pinctrl/pinctrl-imx.c
> index 44e9726..1725e07 100644
> --- a/drivers/pinctrl/pinctrl-imx.c
> +++ b/drivers/pinctrl/pinctrl-imx.c
> @@ -54,6 +54,34 @@ struct imx_pinctrl {
>  	const struct imx_pinctrl_soc_info *info;
>  };
>  
> +static struct imx_pinctrl *imx_pinctrl;
> +/*
> + * Set bits for general purpose registers
> + */
> +int imx_pinctrl_gpr_write(u8 gpr, u32 mask, u32 value)
> +{
> +	u32 reg;
> +
> +	if (!imx_pinctrl)
> +		return -EPROBE_DEFER;
> +
> +	reg = readl(imx_pinctrl->base + gpr);
> +	reg &= ~mask;
> +	writel(reg | value, imx_pinctrl->base + gpr);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(imx_pinctrl_gpr_write);
> +
> +int imx_pinctrl_gpr_read(u8 gpr)
> +{
> +	if (!imx_pinctrl)
> +		return -EPROBE_DEFER;
> +
> +	return readl(imx_pinctrl->base + gpr);
>   
Suppose the MSB of the register content is 1, how does the caller 
distinguish if the function return an error or return a register content?