Re: [PATCH v4 2/2] mtd: nand: sunxi: add reset line support

[Boris Brezillon]

On Sun, 19 Jun 2016 23:40:35 +0800
Icenowy Zheng <icenowy@xxxxxxxx> wrote:

> The NAND controller on some sun8i chips needs its reset line to be deasserted
> before they can enter working state. This commit added the reset line process
> to the driver.
> 
> Signed-off-by: Icenowy Zheng <icenowy@xxxxxxxx>
> ---
> Changes in v2:
>   - Corrected the error checking code of reset line.
> 
> Changes in v3:
>   - Corrected a more serious error brought in the "fix" of v2.
> 
> Changes in v4:
>   - Removed unneeded code block after "else".
> 
>  drivers/mtd/nand/sunxi_nand.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/mtd/nand/sunxi_nand.c b/drivers/mtd/nand/sunxi_nand.c
> index a83a690..b37075b 100644
> --- a/drivers/mtd/nand/sunxi_nand.c
> +++ b/drivers/mtd/nand/sunxi_nand.c
> @@ -39,6 +39,7 @@
>  #include <linux/gpio.h>
>  #include <linux/interrupt.h>
>  #include <linux/iopoll.h>
> +#include <linux/reset.h>
>  
>  #define NFC_REG_CTL		0x0000
>  #define NFC_REG_ST		0x0004
> @@ -269,6 +270,7 @@ struct sunxi_nfc {
>  	void __iomem *regs;
>  	struct clk *ahb_clk;
>  	struct clk *mod_clk;
> +	struct reset_control *reset;
>  	unsigned long assigned_cs;
>  	unsigned long clk_rate;
>  	struct list_head chips;
> @@ -1871,6 +1873,19 @@ static int sunxi_nfc_probe(struct platform_device *pdev)
>  	if (ret)
>  		goto out_ahb_clk_unprepare;
>  
> +	nfc->reset = devm_reset_control_get_optional(dev, "ahb");
> +
> +	if (!IS_ERR(nfc->reset)) {
> +		ret = reset_control_deassert(nfc->reset);
> +		if (ret) {
> +			dev_err(dev, "reset err %d\n", ret);
> +			goto out_mod_clk_unprepare;
> +		}
> +	}
> +	else if (PTR_ERR(nfc->reset) != -ENOENT) {

	} else if (...) {

> +		return PTR_ERR(nfc->reset);
> +	}
> +
>  	ret = sunxi_nfc_rst(nfc);
>  	if (ret)
>  		goto out_mod_clk_unprepare;


And you should probably reassert the reset line in case of errors and
in the ->remove() hook.