Re: [net-next,PATCH] enetc: Set eMDIO MDC rate to 2.5 MHz only on i.MX95

[Jakub Kicinski <kuba@kernel.org>]

On Mon, 05 Oct 2026 15:30:10 +0000 netdev-bot+sashiko@kernel.org wrote:
> > -#define ENETC_EMDIO_CFG \
> > +#define ENETC_EMDIO_CFG(mdc_div) \
> >  	(MDIO_CFG_HOLD(2) | \
> > -	 MDIO_CFG_CLKDIV(66) | \
> > +	 MDIO_CFG_CLKDIV(mdc_div) | \
> >  	 MDIO_CFG_NEG)  
> 
> [Severity: High]
> What divider do the other users of these accessors get?
> 
> The exported enetc_mdio_read_c22(), enetc_mdio_write_c22(),
> enetc_mdio_read_c45() and enetc_mdio_write_c45() are shared with several
> bus constructors. Only enetc_pci_mdio_probe() sets mdc_div.
> 
> These constructors install the same accessors but set only hw and
> mdio_base:
> 
>   enetc_mdio_probe() in enetc_pf_common.c (PF external MDIO, LS1028A
>   and ENETC4)
>   enetc_imdio_create() in enetc_pf_common.c (internal Lynx PCS MDIO)
>   netc_port_create_emdio_bus() in drivers/net/dsa/netc/netc_main.c
>   vsc9959_mdio_bus_alloc() in drivers/net/dsa/ocelot/felix_vsc9959.c
> 
> For example:
> 
> enetc_pf_common.c:enetc_mdio_probe() {
>     ...
>     bus = devm_mdiobus_alloc_size(dev, sizeof(*mdio_priv));
>     ...
>     mdio_priv->hw = &pf->si->hw;
>     if (is_enetc_rev1(pf->si))
>         mdio_priv->mdio_base = ENETC_EMDIO_BASE;
>     else
>         mdio_priv->mdio_base = ENETC4_EMDIO_BASE;
>     ...
> }
> 
> mdiobus_alloc_size() allocates the priv area with kzalloc(), so mdc_div
> stays 0. MDIO_CFG_CLKDIV(x) is ((((x) >> 1) & 0xff) << 8).
> 
> As a result, every C22/C45 transaction on these buses would write a zero
> clock divider into ENETC_MDIO_CFG. Before 587acb86d646 the value was 258,
> and after it the value was 66.

Looks legit.
-- 
pw-bot: cr