linux-kernel - Re: [PATCH v3] net: mdiobus: Add a function to deassert reset

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Message-ID: <KL1PR01MB5448316A031146A449F87BF9E6749@KL1PR01MB5448.apcprd01.prod.exchangelabs.com>
Date:   Thu, 11 May 2023 11:19:52 +0800
From:   Yan Wang <rk.code@...look.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     hkallweit1@...il.com, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux@...linux.org.uk
Subject: Re: [PATCH v3] net: mdiobus: Add a function to deassert reset



On 5/11/2023 6:15 AM, Andrew Lunn wrote:
>> +static void fwnode_mdiobus_pre_enable_phy(struct fwnode_handle *fwnode)
>> +{
>> +	struct gpio_desc *reset;
>> +
>> +	reset = fwnode_gpiod_get_index(fwnode, "reset", 0, GPIOD_OUT_HIGH, NULL);
>> +	if (IS_ERR(reset) && PTR_ERR(reset) != -EPROBE_DEFER)
>> +		return;
>> +
>> +	usleep_range(100, 200);
>> +	gpiod_set_value_cansleep(reset, 0);
>> +	/*Release the reset pin,it needs to be registered with the PHY.*/
>> +	gpiod_put(reset);
> You are still putting it into reset, and then taking it out of
> reset. This is what i said should not be done. Please only take it out
> of reset if it is in reset.
>
> Also, you ignored my comments about delay after reset.
>
> Documentation/devicetree/bindings/net/ethernet-phy.yaml says:
>
>    reset-gpios:
>      maxItems: 1
>      description:
>        The GPIO phandle and specifier for the PHY reset signal.
>
>    reset-assert-us:
>      description:
>        Delay after the reset was asserted in microseconds. If this
>        property is missing the delay will be skipped.
>
>    reset-deassert-us:
>      description:
>        Delay after the reset was deasserted in microseconds. If
>        this property is missing the delay will be skipped.
>
> You are deasserting the reset, so you should look for this property,
> and if it is there, delay for that amount. Some PHYs take a while
> before they will respond on the bus.
I'm very sorry, I forgot. Thank you
>         Andrew