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

Boris Brezillon
2016-06-19T12:06:57Z

+Philipp

On Sun, 19 Jun 2016 19:37:39 +0800
Icenowy Zheng <icenowy@aosc.xyz> 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@aosc.xyz>
> ---
> drivers/mtd/nand/sunxi_nand.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/drivers/mtd/nand/sunxi_nand.c b/drivers/mtd/nand/sunxi_nand.c
> index a83a690..1502748 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 +1873,18 @@ 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 (PTR_ERR(nfc->reset) == -EPROBE_DEFER)
> + return PTR_ERR(nfc->reset);

Actually you should test for != -ENOENT, because all error codes except
this one should stop the ->probe().

BTW, this devm_reset_control_get_optional() is really weird. While most
_optional() methods return NULL when the element is not defined in the
DT, this one returns -ENOTENT, which makes it impossible to
differentiate a real error from a undefined reset line (which is a
valid case for _optional()).

Philipp, is there a good reason for doing that?

> +
> + 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;
> + }
> + }
> +