netdev - Re: [PATCH net-next] net: bgmac: support MDIO described in DT

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Date:   Mon, 20 Sep 2021 09:11:08 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Rafał Miłecki <zajec5@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, devicetree@...r.kernel.org,
        bcm-kernel-feedback-list@...adcom.com,
        Rafał Miłecki <rafal@...ecki.pl>
Subject: Re: [PATCH net-next] net: bgmac: support MDIO described in DT

On 9/20/21 5:34 AM, Rafał Miłecki wrote:
> From: Rafał Miłecki <rafal@...ecki.pl>
> 
> Check ethernet controller DT node for "mdio" subnode and use it with
> of_mdiobus_register() when present. That allows specifying MDIO and its
> PHY devices in a standard DT based way.
> 
> This is required for BCM53573 SoC support which has an MDIO attached
> switch.
> 
> Signed-off-by: Rafał Miłecki <rafal@...ecki.pl>
> ---
>  drivers/net/ethernet/broadcom/bgmac-bcma-mdio.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/broadcom/bgmac-bcma-mdio.c b/drivers/net/ethernet/broadcom/bgmac-bcma-mdio.c
> index 6ce80cbcb48e..086739e4f40a 100644
> --- a/drivers/net/ethernet/broadcom/bgmac-bcma-mdio.c
> +++ b/drivers/net/ethernet/broadcom/bgmac-bcma-mdio.c
> @@ -10,6 +10,7 @@
>  
>  #include <linux/bcma/bcma.h>
>  #include <linux/brcmphy.h>
> +#include <linux/of_mdio.h>
>  #include "bgmac.h"
>  
>  static bool bcma_mdio_wait_value(struct bcma_device *core, u16 reg, u32 mask,
> @@ -211,6 +212,7 @@ struct mii_bus *bcma_mdio_mii_register(struct bgmac *bgmac)
>  {
>  	struct bcma_device *core = bgmac->bcma.core;
>  	struct mii_bus *mii_bus;
> +	struct device_node *np;
>  	int err;
>  
>  	mii_bus = mdiobus_alloc();
> @@ -229,7 +231,9 @@ struct mii_bus *bcma_mdio_mii_register(struct bgmac *bgmac)
>  	mii_bus->parent = &core->dev;
>  	mii_bus->phy_mask = ~(1 << bgmac->phyaddr);
>  
> -	err = mdiobus_register(mii_bus);
> +	np = of_get_child_by_name(core->dev.of_node, "mdio");

I believe this leaks np and the use case is not exactly clear to me
here. AFAICT the Northstar SoCs have two MDIO controllers: one for
internal PHYs and one for external PHYs which how you would attach a
switch to the chip (in chipcommonA). Is 53573 somewhat different here?
What is the MDIO bus driver that is being used?
-- 
Florian