Subject: Re: [net-next RFC PATCH v2 3/3] net: phy: Add Airoha AN8855 Internal Switch Gigabit PHY

From: Christian Marangi <[email-masked]>
Date: Fri, 25 Oct 2024 13:01:31 +0200

On Wed, Oct 23, 2024 at 07:07:08PM +0200, Christian Marangi wrote:
> On Wed, Oct 23, 2024 at 07:00:22PM +0200, Andrew Lunn wrote:
> > > +static int an8855_config_init(struct phy_device *phydev)
> > > +{
> > > +	struct air_an8855_priv *priv = phydev->priv;
> > > +	int ret;
> > > +
> > > +	/* Enable HW auto downshift */
> > > +	ret = phy_write(phydev, AN8855_PHY_PAGE_CTRL, AN8855_PHY_EXT_PAGE);
> > > +	if (ret)
> > > +		return ret;
> > > +	ret = phy_set_bits(phydev, AN8855_PHY_EXT_REG_14,
> > > +			   AN8855_PHY_EN_DOWN_SHFIT);
> > > +	if (ret)
> > > +		return ret;
> > > +	ret = phy_write(phydev, AN8855_PHY_PAGE_CTRL, AN8855_PHY_NORMAL_PAGE);
> > > +	if (ret)
> > > +		return ret;
> > 
> > There are locking issues here, which is why we have the helpers
> > phy_select_page() and phy_restore_page(). The air_en8811h.c gets this
> > right.
> 
> Ugh didn't think about it... The switch address is shared with the PHY
> so yes this is a problem.
> 
> Consider that this page thing comes from my speculation... Not really
> use if 1f select page... 
> From what I observed
> 0x0 PHY page
> 0x1 this strange EXT
> 0x4 acess switch register (every PHY can access the switch)
>

Just to followup on this... I checked air_en8811h registers again and
they match MII access to the switch so yes my speculation is correct.

Also extra happy since I now know what those magic values means at least
for MII.

> > 
> > Is there anything in common with the en8811h? Does it also support
> > downshift? Can its LED code be used here?
> > 
> 
> For some reason part of the LED are controlled by the switch and some
> are by the PHY. I still have to investigate that (not giving priority to
> it... just on my todo)
> 
> For downshift as you notice it's a single bit with no count...
> From their comments in the original driver it's said "Enable HW
> autodownshift"
> 
> Trying to reach them but currently it's all very obscure.
> 
> -- 
> 	Ansuel

-- 
	Ansuel