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SubjectRe: [PATCH 01/20] net: phy: realtek: Fix events detection failure in LPI mode
On Mon, Feb 08, 2021 at 09:14:02PM +0100, Heiner Kallweit wrote:
> On 08.02.2021 15:03, Serge Semin wrote:
> > It has been noticed that RTL8211E PHY stops detecting and reporting events
> > when EEE is successfully advertised and RXC stopping in LPI is enabled.
> > The freeze happens right after 3.0.10 bit (PC1R "Clock Stop Enable"
> > register) is set. At the same time LED2 stops blinking as if EEE mode has
> > been disabled. Notably the network traffic still flows through the PHY
> > with no obvious problem. Anyway if any MDIO read procedure is performed
> > after the "RXC stop in LPI" mode is enabled PHY gets to be unfrozen, LED2
> > starts blinking and PHY interrupts happens again. The problem has been
> > noticed on RTL8211E PHY working together with DW GMAC 3.73a MAC and
> > reporting its event via a dedicated IRQ signal. (Obviously the problem has
> > been unnoticed in the polling mode, since it gets naturally fixed by the
> > periodic MDIO read procedure from the PHY status register - BMSR.)
> >
> > In order to fix that problem we suggest to locally re-implement the MMD
> > write method for RTL8211E PHY and perform a dummy read right after the
> > PC1R register is accessed to enable the RXC stopping in LPI mode.
> >
> > Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
> > ---
> > drivers/net/phy/realtek.c | 37 +++++++++++++++++++++++++++++++++++++
> > 1 file changed, 37 insertions(+)
> >
> > diff --git a/drivers/net/phy/realtek.c b/drivers/net/phy/realtek.c
> > index 99ecd6c4c15a..cbb86c257aae 100644
> > --- a/drivers/net/phy/realtek.c
> > +++ b/drivers/net/phy/realtek.c
> > @@ -559,6 +559,42 @@ static int rtl822x_write_mmd(struct phy_device *phydev, int devnum, u16 regnum,
> > return ret;
> > }
> >
> > +static int rtl8211e_write_mmd(struct phy_device *phydev, int devnum, u16 regnum,
> > + u16 val)
> > +{
> > + int ret;
> > +
> > + /* Write to the MMD registers by using the standard control/data pair.
> > + * The only difference is that we need to perform a dummy read after
> > + * the PC1R.CLKSTOP_EN bit is set. It's required to workaround an issue
> > + * of a partial core freeze so LED2 stops blinking in EEE mode, PHY
> > + * stops detecting the link change and raising IRQs until any read from
> > + * its registers performed. That happens only if and right after the PHY
> > + * is enabled to stop RXC in LPI mode.
> > + */
> > + ret = __phy_write(phydev, MII_MMD_CTRL, devnum);
> > + if (ret)
> > + return ret;
> > +
> > + ret = __phy_write(phydev, MII_MMD_DATA, regnum);
> > + if (ret)
> > + return ret;
> > +
> > + ret = __phy_write(phydev, MII_MMD_CTRL, devnum | MII_MMD_CTRL_NOINCR);
> > + if (ret)
> > + return ret;
> > +
>

> Nice analysis. Alternatively to duplicating this code piece we could
> export mmd_phy_indirect(). But up to you.

I also considered creating a generic method to access the MMD
registers of a generic PHY, something like phy_read()/phy_write(), but
for MMD (alas just exporting mmd_phy_indirect() would not be enough).
But as I see it such methods need to be created only after we get to
have at least several places with duplicating direct MMD-read/write
patterns. Doing that just for a single place seems redundant. Anyway it's
up to maintainers to decide whether they want to see a generic part
of the phy_read_mmd()/phy_write_mmd() methods being detached and
exported as something like genphy_{read,write}_mmd() methods. I can do
that in v2 if you ask me to.

-Sergey

>
> > + ret = __phy_write(phydev, MII_MMD_DATA, val);
> > + if (ret)
> > + return ret;
> > +
> > + if (devnum == MDIO_MMD_PCS && regnum == MDIO_CTRL1 &&
> > + val & MDIO_PCS_CTRL1_CLKSTOP_EN)
> > + ret = __phy_read(phydev, MII_MMD_DATA);
> > +
> > + return ret < 0 ? ret : 0;
> > +}
> > +
> > static int rtl822x_get_features(struct phy_device *phydev)
> > {
> > int val;
> > @@ -725,6 +761,7 @@ static struct phy_driver realtek_drvs[] = {
> > .resume = genphy_resume,
> > .read_page = rtl821x_read_page,
> > .write_page = rtl821x_write_page,
> > + .write_mmd = rtl8211e_write_mmd,
> > }, {
> > PHY_ID_MATCH_EXACT(0x001cc916),
> > .name = "RTL8211F Gigabit Ethernet",
> >
>

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