Re: [PATCH AUTOSEL 6.8 39/68] net: mdio: mdio-bcm-unimac: Manage clock around I/O accesses

[Sasha Levin]

On Tue, Apr 02, 2024 at 05:41:44AM -0700, Florian Fainelli wrote:
> On 3/29/2024 5:25 AM, Sasha Levin wrote:
> > From: Florian Fainelli <florian.fainelli@xxxxxxxxxxxx>
> >
> > [ Upstream commit ee975351cf0c2a11cdf97eae58265c126cb32850 ]
> >
> > Up until now we have managed not to have the mdio-bcm-unimac manage its
> > clock except during probe and suspend/resume. This works most of the
> > time, except where it does not.
> >
> > With a fully modular build, we can get into a situation whereby the
> > GENET driver is fully registered, and so is the mdio-bcm-unimac driver,
> > however the Ethernet PHY driver is not yet, because it depends on a
> > resource that is not yet available (e.g.: GPIO provider). In that state,
> > the network device is not usable yet, and so to conserve power, the
> > GENET driver will have turned off its "main" clock which feeds its MDIO
> > controller.
> >
> > When the PHY driver finally probes however, we make an access to the PHY
> > registers to e.g.: disable interrupts, and this causes a bus error
> > within the MDIO controller space because the MDIO controller clock(s)
> > are turned off.
> >
> > To remedy that, we manage the clock around all of the I/O accesses to
> > the hardware which are done exclusively during read, write and clock
> > divider configuration.
> >
> > This ensures that the register space is accessible, and this also
> > ensures that there are not unnecessarily elevated reference counts
> > keeping the clocks active when the network device is administratively
> > turned off. It would be the case with the previous way of managing the
> > clock.
> >
> > Reviewed-by: Jacob Keller <jacob.e.keller@xxxxxxxxx>
> > Signed-off-by: Florian Fainelli <florian.fainelli@xxxxxxxxxxxx>
> > Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
>
> Please drop this patch, it is usable in isolation and needs 2 
> additional patches to be meaningful:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ee2b4cf8b281606bbf332cbd73ce2a73eac417f0
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> /commit/?id=ba0b78371c46b2104197ff2c244f13f011ddfa80

Ack, thanks!

--
Thanks,
Sasha