Re: [PATCH] net: broadcom: Add PTP_1588_CLOCK_OPTIONAL dependency for BCMGENET under ARCH_BCM2835

[Florian Fainelli]

On 11/29/22 03:58, Arnd Bergmann wrote:
> [Florian's broadcom.com address bounces, adding him to Cc
> with his gmail address]

Yes, because it's not a valid email address :) it's either lastname, or 
first.lastname.

> On Tue, Nov 29, 2022, at 12:56, Arnd Bergmann wrote:
> > On Tue, Nov 29, 2022, at 04:18, Jakub Kicinski wrote:
> > > On Fri, 25 Nov 2022 19:50:03 +0800 YueHaibing wrote:
> > > > diff --git a/drivers/net/ethernet/broadcom/Kconfig b/drivers/net/ethernet/broadcom/Kconfig
> > > > index 55dfdb34e37b..f4ca0c6c0f51 100644
> > > > --- a/drivers/net/ethernet/broadcom/Kconfig
> > > > +++ b/drivers/net/ethernet/broadcom/Kconfig
> > > > @@ -71,13 +71,14 @@ config BCM63XX_ENET
> > > >   config BCMGENET
> > > >   	tristate "Broadcom GENET internal MAC support"
> > > >   	depends on HAS_IOMEM
> > > > +	depends on PTP_1588_CLOCK_OPTIONAL || !ARCH_BCM2835
> > > >   	select MII
> > > >   	select PHYLIB
> > > >   	select FIXED_PHY
> > > >   	select BCM7XXX_PHY
> > > >   	select MDIO_BCM_UNIMAC
> > > >   	select DIMLIB
> > > > -	select BROADCOM_PHY if (ARCH_BCM2835 && PTP_1588_CLOCK_OPTIONAL)
> > > > +	select BROADCOM_PHY if ARCH_BCM2835
> > > >   	help
> > > >   	  This driver supports the built-in Ethernet MACs found in the
> > > >   	  Broadcom BCM7xxx Set Top Box family chipset.
> > >
> > > What's the code path that leads to the failure? I want to double check
> > > that the driver is handling the PTP registration return codes correctly.
> > > IIUC this is a source of misunderstandings in the PTP API.
> > >
> > > Richard, here's the original report:
> > > https://lore.kernel.org/all/CA+G9fYvKfbJHcMZtybf_0Ru3+6fKPg9HwWTOhdCLrOBXMaeG1A@xxxxxxxxxxxxxx
> >
> > The original report was for a different bug that resulted in the
> > BROADCOM_PHY driver not being selectable at all.
> >
> > The remaining problem here is this configuration:
> >
> > CONFIG_ARM=y
> > CONFIG_BCM2835=y
> > CONFIG_BCMGENET=y
> > CONFIG_PTP_1588_CLOCK=m
> > CONFIG_PTP_1588_CLOCK_OPTIONAL=m
> > CONFIG_BROADCOM_PHY=m
> >
> > In this case, BCMGENET should 'select BROADCOM_PHY' to make the
> > driver work correctly, but fails to do this because of the
> > dependency. During early boot, this means it cannot access the
> > PHY because that is in a loadable module, despite commit
> > 99addbe31f55 ("net: broadcom: Select BROADCOM_PHY for BCMGENET")
> > trying to ensure that it could.

I don't believe this is the failure mechanism because there is always a 
fallback to the Generic PHY driver, the issue is that we have configured 
a specific RGMII mode in the Device Tree that is acted on by both the 
Ethernet MAC and the PHY in a way that is electrically incompatible 
unless the proper PHY driver is also enabled such that the RGMII mode is 
enabled on the PHY side.
--
Florian