Re: [Qemu-devel] [PATCH v3] e1000: clean up phyreg_writeops/set_phy_ctrl

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jul 02, 2014 at 12:12:30PM +0300, Michael S. Tsirkin wrote:
> On Tue, Jul 01, 2014 at 03:03:48PM -0400, Gabriel L. Somlo wrote:
> > Make phyreg_writeops responsible for actually writing their
> > respective phy registers. The only current instance of
> > phyreg_writeops is set_phy_ctrl(), which we modify to actually
> > write the register, while also correctly handling reserved and
> > self-clearing bits.
> > 
> > have_autoneg() does not need to check for MII_CR_RESTART_AUTO_NEG,
> > since the only time the flag comes into play is during set_phy_ctrl(),
> > and never actually gets written to the phy control register. We also
> > move it in front of set_phy_ctrl(), to avoid a forward declaration.
> > 
> > Signed-off-by: Gabriel Somlo <somlo@cmu.edu>
> > ---
> 
> 
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> 
> Applied, thanks!

And just to clarify (I'd like to add this to the commit log)
we are fixing a minor bug here: MII_CR_RESTART_AUTO_NEG and MII_CR_RESET
aren't self-clearing as they should be, and low 5 bits aren't RO
as they should be.


> > Michael, Stefan:
> > 
> > Here's a new version of this patch with slightly better (IMHO) formatting.
> > I think the merits are 1. handling bits which are reserved or self
> > clearing; and 2. eliminating the surprise of a "write op" that does not
> > actually write to its register :)
> > 
> > Regarding the "sibling" patch originally accompanying this one (which
> > increased the timer delay for autonegotiation), I'll take a while
> > longer to figure out what's really going on, so I'll send out a separate
> > patch if/when that happens.
> > 
> > Please apply (or review/critique) this one independently.
> > 
> > Thanks,
> >   Gabriel
> > 
> >  hw/net/e1000.c | 31 +++++++++++++++++--------------
> >  1 file changed, 17 insertions(+), 14 deletions(-)
> > 
> > diff --git a/hw/net/e1000.c b/hw/net/e1000.c
> > index 0fc29a0..04c0f91 100644
> > --- a/hw/net/e1000.c
> > +++ b/hw/net/e1000.c
> > @@ -186,21 +186,31 @@ e1000_link_up(E1000State *s)
> >      s->phy_reg[PHY_STATUS] |= MII_SR_LINK_STATUS;
> >  }
> >  
> > +static bool
> > +have_autoneg(E1000State *s)
> > +{
> > +    return (s->compat_flags & E1000_FLAG_AUTONEG) &&
> > +           (s->phy_reg[PHY_CTRL] & MII_CR_AUTO_NEG_EN);
> > +}
> > +
> >  static void
> >  set_phy_ctrl(E1000State *s, int index, uint16_t val)
> >  {
> > +    /* bits 0-5 reserved; MII_CR_[RESTART_AUTO_NEG,RESET] are self clearing */
> > +    s->phy_reg[PHY_CTRL] = val & ~(0x3f |
> > +                                   MII_CR_RESET |
> > +                                   MII_CR_RESTART_AUTO_NEG);
> > +
> >      /*
> >       * QEMU 1.3 does not support link auto-negotiation emulation, so if we
> >       * migrate during auto negotiation, after migration the link will be
> >       * down.
> >       */
> > -    if (!(s->compat_flags & E1000_FLAG_AUTONEG)) {
> > -        return;
> > -    }
> > -    if ((val & MII_CR_AUTO_NEG_EN) && (val & MII_CR_RESTART_AUTO_NEG)) {
> > +    if (have_autoneg(s) && (val & MII_CR_RESTART_AUTO_NEG)) {
> >          e1000_link_down(s);
> >          DBGOUT(PHY, "Start link auto negotiation\n");
> > -        timer_mod(s->autoneg_timer, qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + 500);
> > +        timer_mod(s->autoneg_timer,
> > +                  qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + 500);
> >      }
> >  }
> >  
> > @@ -446,8 +456,9 @@ set_mdic(E1000State *s, int index, uint32_t val)
> >          } else {
> >              if (addr < NPHYWRITEOPS && phyreg_writeops[addr]) {
> >                  phyreg_writeops[addr](s, index, data);
> > +            } else {
> > +                s->phy_reg[addr] = data;
> >              }
> > -            s->phy_reg[addr] = data;
> >          }
> >      }
> >      s->mac_reg[MDIC] = val | E1000_MDIC_READY;
> > @@ -848,14 +859,6 @@ receive_filter(E1000State *s, const uint8_t *buf, int size)
> >      return 0;
> >  }
> >  
> > -static bool
> > -have_autoneg(E1000State *s)
> > -{
> > -    return (s->compat_flags & E1000_FLAG_AUTONEG) &&
> > -           (s->phy_reg[PHY_CTRL] & MII_CR_AUTO_NEG_EN) &&
> > -           (s->phy_reg[PHY_CTRL] & MII_CR_RESTART_AUTO_NEG);
> > -}
> > -
> >  static void
> >  e1000_set_link_status(NetClientState *nc)
> >  {
> > -- 
> > 1.9.3