lkml.org 
[lkml]   [2022]   [Jul]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH net v1 1/1] net: dsa: microchip: don't try do read Gbit registers on non Gbit chips
    On Fri, Jul 29, 2022 at 11:05:13AM +0200, Oleksij Rempel wrote:
    > On Thu, Jul 28, 2022 at 03:25:35PM +0200, Andrew Lunn wrote:
    > > On Thu, Jul 28, 2022 at 03:17:25PM +0200, Oleksij Rempel wrote:
    > > > Do not try to read not existing or wrong register on chips without
    > > > GBIT_SUPPORT.
    > > >
    > > > Fixes: c2e866911e25 ("net: dsa: microchip: break KSZ9477 DSA driver into two files")
    > > > Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
    > > > ---
    > > > drivers/net/dsa/microchip/ksz9477.c | 8 +++++++-
    > > > 1 file changed, 7 insertions(+), 1 deletion(-)
    > > >
    > > > diff --git a/drivers/net/dsa/microchip/ksz9477.c b/drivers/net/dsa/microchip/ksz9477.c
    > > > index c73bb6d383ad..f6bbd9646c85 100644
    > > > --- a/drivers/net/dsa/microchip/ksz9477.c
    > > > +++ b/drivers/net/dsa/microchip/ksz9477.c
    > > > @@ -316,7 +316,13 @@ void ksz9477_r_phy(struct ksz_device *dev, u16 addr, u16 reg, u16 *data)
    > > > break;
    > > > }
    > > > } else {
    > > > - ksz_pread16(dev, addr, 0x100 + (reg << 1), &val);
    > > > + /* No gigabit support. Do not read wrong registers. */
    > > > + if (!(dev->features & GBIT_SUPPORT) &&
    > > > + (reg == MII_CTRL1000 || reg == MII_ESTATUS ||
    > > > + reg == MII_STAT1000))
    > >
    > > Does this actually happen?
    > >
    > > If i remember this code correctly, it tries to make the oddly looking
    > > PHY look like a normal PHY. phylib is then used to drive the PHY?
    > >
    > > If i have that correct, why is phylib trying to read these registers?
    > > It should know there is no 1G support, and should skip them.
    >
    > It looks like currently undocumented silicon errata. According to the
    > data sheet, the BMSR_ESTATEN should not be set BMSR_ERCAP, but this bits
    > are set.
    >
    > The question is what is the proper place to implement it. There is same
    > PHYid for most KSZ switch PHYs, it is no possible to detect it by PHYid.
    > I have following options:
    > - add chips specific quirk in the ksz9477_r_phy(), just remove
    > BMSR_ESTATEN and BMSR_ERCAP.
    > - notify about errata over get_phy_flags and implement get_caps quirk in
    > the PHY driver.

    I would do the first. The DSA driver is already doing some emulation
    of a normal PHY, so it seems odd to push a workaround into the PHY
    driver when it can be part of the emulation.

    Andrew

    \
     
     \ /
      Last update: 2022-07-29 15:15    [W:3.089 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site