Re: [PATCH] net: phy: broadcom: add support for BCM5221 phy

[Giulio Benetti]

Hello Florian,

thanks for reviewing,

On 12/08/23 01:52, Florian Fainelli wrote:
> On 8/11/2023 2:53 PM, Giulio Benetti wrote:
> > This patch adds the BCM5221 PHY support by reusing
> > brcm_fet_config_intr() and brcm_fet_handle_interrupt() and
> > implementing config_init()/suspend()/resume().
> >
> > Sponsored by: Tekvox Inc.
> > Cc: Jim Reinhart <jimr@xxxxxxxxxx>
> > Cc: James Autry <jautry@xxxxxxxxxx>
> > Cc: Matthew Maron <matthewm@xxxxxxxxxx>
> > Signed-off-by: Giulio Benetti <giulio.benetti@xxxxxxxxxxxxxxxxxxxxxx>
>
> Looks good, few comments below.
>
> > ---
> >   drivers/net/phy/broadcom.c | 144 +++++++++++++++++++++++++++++++++++++
> >   include/linux/brcmphy.h    |   8 +++
> >   2 files changed, 152 insertions(+)
> >
> > diff --git a/drivers/net/phy/broadcom.c b/drivers/net/phy/broadcom.c
> > index 59cae0d808aa..99f6c0485f01 100644
> > --- a/drivers/net/phy/broadcom.c
> > +++ b/drivers/net/phy/broadcom.c
> > @@ -754,6 +754,84 @@ static int brcm_fet_config_init(struct phy_device 
> > *phydev)
> >       return err;
> >   }
> > +static int bcm5221_config_init(struct phy_device *phydev)
> > +{
>
> Very similar to brcm_fet_config_init() except that you configure fewer 
> interrupt sources, do not have the LED mode programming and your MDI-X 
> programming is done via a 10BaseT specific register rather than the shadow.
>
> Can you consider adding parameters to brcm_fet_config_init() such that 
> you can specify the 5221 specific settings such as the interrupt mask 
> for instance?

So if I've understood correctly I should drop bcm5221_config_init() and
use brcm_fet_config_init() by checking the struct phy_driver .phy_id to
be PHY_ID_BCM5221.

> This should help address the locking that Russell suggested.

But I don't understand how this can help to prevent the locking Russell
suggested, can you please elaborate more or point me and example?
As far as I've understood I should take care to lock sections to prevent
from interrupts to occur during shadow mode switching, is it correct?
So maybe you mean that if I do this in brcm_fet_config_init() it will be
fixed for the other phys using brcm_fet_config_init(), correct?

> [snip]
> > +static int bcm5221_suspend(struct phy_device *phydev)
> > +{
> > +    int reg, err, err2, brcmtest;
> > +
> > +    /* Enable shadow register access */
> > +    brcmtest = phy_read(phydev, MII_BRCM_FET_BRCMTEST);
> > +    if (brcmtest < 0)
> > +        return brcmtest;
> > +
> > +    reg = brcmtest | MII_BRCM_FET_BT_SRE;
> > +
> > +    err = phy_write(phydev, MII_BRCM_FET_BRCMTEST, reg);
> > +    if (err < 0)
> > +        return err;
> > +
> > +    /* Force Low Power Mode with clock enabled */
> > +    err = phy_set_bits(phydev, MII_BRCM_FET_SHDW_AUXMODE4,
> > +               BCM5221_SHDW_AM4_EN_CLK_LPM |
> > +               BCM5221_SHDW_AM4_FORCE_LPM);
> > +
> > +    /* Disable shadow register access */
> > +    err2 = phy_write(phydev, MII_BRCM_FET_BRCMTEST, brcmtest);
> > +    if (!err)
> > +        err = err2;
> > +
> > +    return err;
> > +}
>
> bcm5221_suspend() is essentially brcm_fet_suspend() minus the setting of 
> the BMCR.PDOWN bit, can you consider factoring brcm_fet_suspend() into a 
> helper that can decide whether to set the power down bit or not? Does 
> not brcm_fet_suspend() work as-is?

Sure, I will,

> > +
> > +static int bcm5221_resume(struct phy_device *phydev)
> > +{
>
> This should really be calling bcm5221_config_init() here, if the PHY was 
> on a power island that is powered off during system suspend, 
> bcm5221_resume() would not be restoring the auto-power down that is set 
> during config_init(), probably not desired because that means you will 
> burn power when the cable is disconnected...

oh yes! You're right, I will then drop bcm5221_resume() in favor of 
bcm5221_config_init(), so brcm_fet_config_init() with phy_id == 
PHY_ID_BCM5221 checks.

Thanks again
Best regards
--
Giulio Benetti
CEO&CTO@Benetti Engineering sas