Re: [PATCH] gpio: gpio-rcar: Support S2RAM

[Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>]

Hi Kaneko-san,

On Wed, Dec 6, 2017 at 7:48 PM, Yoshihiro Kaneko <ykaneko0929@xxxxxxxxx> wrote:
> From: Hien Dang <hien.dang.eb@xxxxxxxxxxx>
>
> This patch adds an implementation that saves and restores the state of
> GPIO configuration on suspend and resume.
>
> Signed-off-by: Hien Dang <hien.dang.eb@xxxxxxxxxxx>
> Signed-off-by: Takeshi Kihara <takeshi.kihara.df@xxxxxxxxxxx>
> Signed-off-by: Yoshihiro Kaneko <ykaneko0929@xxxxxxxxx>

Thanks for your patch!

> --- a/drivers/gpio/gpio-rcar.c
> +++ b/drivers/gpio/gpio-rcar.c
> @@ -31,6 +31,16 @@
>  #include <linux/spinlock.h>
>  #include <linux/slab.h>
>
> +struct gpio_rcar_bank_info {
> +       bool iointsel;
> +       bool inoutsel;
> +       bool outdt;
> +       bool active_high_rising_edge;
> +       bool level_trigger;
> +       bool both;
> +       bool intmsk;
> +};

So for each GPIO, you save 7 bools = 7 bytes.

>  struct gpio_rcar_priv {
>         void __iomem *base;
>         spinlock_t lock;
> @@ -41,6 +51,7 @@ struct gpio_rcar_priv {
>         unsigned int irq_parent;
>         bool has_both_edge_trigger;
>         bool needs_clk;
> +       struct gpio_rcar_bank_info bank_info[32];

That's 32 x 7 = 224 bytes in total.

What about just using 7 u32s instead, one for each register to save?
That way you only need 7 x 4 = 28 bytes, and you can probably optimize
the code to just save/restore the whole register at once.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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