linux-kernel - Re: [PATCH v2] net: mdio: force deassert MDIO reset signal

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Message-ID: <Y8UwrzenvgGw8dns@corigine.com>
Date:   Mon, 16 Jan 2023 12:10:39 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Pierluigi Passaro <pierluigi.p@...iscite.com>
Cc:     andrew@...n.ch, hkallweit1@...il.com, linux@...linux.org.uk,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, eran.m@...iscite.com,
        nate.d@...iscite.com, francesco.f@...iscite.com,
        pierluigi.passaro@...il.com
Subject: Re: [PATCH v2] net: mdio: force deassert MDIO reset signal

On Sun, Jan 15, 2023 at 10:37:46PM +0100, Pierluigi Passaro wrote:
> When the reset gpio is defined within the node of the device tree
> describing the PHY, the reset is initialized and managed only after
> calling the fwnode_mdiobus_phy_device_register function.
> However, before calling it, the MDIO communication is checked by the
> get_phy_device function.
> When this happen and the reset GPIO was somehow previously set down,
> the get_phy_device function fails, preventing the PHY detection.
> These changes force the deassert of the MDIO reset signal before
> checking the MDIO channel.
> The PHY may require a minimum deassert time before being responsive:
> use a reasonable sleep time after forcing the deassert of the MDIO
> reset signal.
> Once done, free the gpio descriptor to allow managing it later.
> 
> Signed-off-by: Pierluigi Passaro <pierluigi.p@...iscite.com>
> Signed-off-by: FrancescoFerraro <francesco.f@...iscite.com>
> ---
>  drivers/net/mdio/fwnode_mdio.c | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/drivers/net/mdio/fwnode_mdio.c b/drivers/net/mdio/fwnode_mdio.c
> index b782c35c4ac1..1f4b8c4c1f60 100644
> --- a/drivers/net/mdio/fwnode_mdio.c
> +++ b/drivers/net/mdio/fwnode_mdio.c
> @@ -8,6 +8,8 @@
>  
>  #include <linux/acpi.h>
>  #include <linux/fwnode_mdio.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/gpio/driver.h>
>  #include <linux/of.h>
>  #include <linux/phy.h>
>  #include <linux/pse-pd/pse.h>
> @@ -118,6 +120,8 @@ int fwnode_mdiobus_register_phy(struct mii_bus *bus,
>  	bool is_c45 = false;
>  	u32 phy_id;
>  	int rc;
> +	int reset_deassert_delay = 0;

nit: it looks like scope of reset_deassert_delay could be reduced
     to the else clause where it is used.

> +	struct gpio_desc *reset_gpio;

nit: reverse xmas tree for local variable declarations

...

Also, if reposting, the target tree for this should be in the subject.
Assuming net-next, that would mean "[PATCH net-next v3]"