Re: [PATCH net-next v3 1/4] phylib: Add device reset delay support

Geert Uytterhoeven
2017-12-05T13:54:11Z

Hi Richard,

On Tue, Dec 5, 2017 at 2:25 PM, Richard Leitner <dev@g0hl1n.net> wrote:
> From: Richard Leitner <richard.leitner@skidata.com>
>
> Some PHYs need a minimum time after the reset gpio was asserted and/or
> deasserted. To ensure we meet these timing requirements add two new
> optional devicetree parameters for the phy: reset-delay-us and
> reset-post-delay-us.

Thanks for your patch!

> This patch depends on the "phylib: Add device reset GPIO support" patch
> submitted by Geert Uytterhoeven/Sergei Shtylyov, see:
> https://patchwork.kernel.org/patch/10090149/

The above paragraph belongs under the "---" line below, as it is not intended
to be preserved in the eternal git history.

> Signed-off-by: Richard Leitner <richard.leitner@skidata.com>

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

Although I have a few suggestions below:

> --- a/drivers/net/phy/mdio_device.c
> +++ b/drivers/net/phy/mdio_device.c
> @@ -118,8 +119,16 @@ EXPORT_SYMBOL(mdio_device_remove);
>
> void mdio_device_reset(struct mdio_device *mdiodev, int value)
> {
> - if (mdiodev->reset)
> - gpiod_set_value(mdiodev->reset, value);
> + if (!mdiodev->reset)
> + return;
> +
> + gpiod_set_value(mdiodev->reset, value);
> +
> + if (value && mdiodev->reset_delay)
> + usleep_range(mdiodev->reset_delay, mdiodev->reset_delay + 100);
> + else if (!value && mdiodev->reset_post_delay)
> + usleep_range(mdiodev->reset_post_delay,
> + mdiodev->reset_post_delay + 100);

I think this can be written simpler using e.g.:

unsigned int delay;

...
delay = value ? mdiodev->reset_delay : mdiodev->reset_post_delay;
if (delay)
usleep_range(delay, delay + 100);

Perhaps the range extension should be relative, e.g.
"delay + min(delay / 10, 100)"?

> --- a/drivers/of/of_mdio.c
> +++ b/drivers/of/of_mdio.c
> @@ -77,6 +77,14 @@ static int of_mdiobus_register_phy(struct mii_bus *mdio,
> if (of_property_read_bool(child, "broken-turn-around"))
> mdio->phy_ignore_ta_mask |= 1 << addr;
>
> + if (of_property_read_u32(child, "reset-delay-us",
> + &phy->mdio.reset_delay))
> + phy->mdio.reset_delay = 0;
> +
> + if (of_property_read_u32(child, "reset-post-delay-us",
> + &phy->mdio.reset_post_delay))
> + phy->mdio.reset_post_delay = 0;

If of_property_read_u32() fails, it doesn't write to its output parameter.
As the structure should be zeroed during allocation, you can just write:

of_property_read_u32(child, "reset-delay-us", &phy->mdio.reset_delay);
of_property_read_u32(child, "reset-post-delay-us",
&phy->mdio.reset_post_delay);

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

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