On Thu, 22 Oct 2020 at 07:41, Benjamin Herrenschmidt
<b...@kernel.crashing.org> wrote:
>
> On Wed, 2020-10-21 at 14:40 +0200, Arnd Bergmann wrote:
> > On Wed, Oct 21, 2020 at 12:39 PM Joel Stanley <j...@jms.id.au> wrote:
> >
> > >
> > > diff --git a/drivers/net/ethernet/faraday/ftgmac100.c
> > > b/drivers/net/ethernet/faraday/ftgmac100.c
> > > index 331d4bdd4a67..15cdfeb135b0 100644
> > > --- a/drivers/net/ethernet/faraday/ftgmac100.c
> > > +++ b/drivers/net/ethernet/faraday/ftgmac100.c
> > > @@ -653,6 +653,11 @@ static bool ftgmac100_tx_complete_packet(struct
> > > ftgmac100 *priv)
> > > ftgmac100_free_tx_packet(priv, pointer, skb, txdes, ctl_stat);
> > > txdes->txdes0 = cpu_to_le32(ctl_stat & priv->txdes0_edotr_mask);
> > >
> > > + /* Ensure the descriptor config is visible before setting the tx
> > > + * pointer.
> > > + */
> > > + smp_wmb();
> > > +
> > > priv->tx_clean_pointer = ftgmac100_next_tx_pointer(priv, pointer);
> > >
> > > return true;
> > > @@ -806,6 +811,11 @@ static netdev_tx_t ftgmac100_hard_start_xmit(struct
> > > sk_buff *skb,
> > > dma_wmb();
> > > first->txdes0 = cpu_to_le32(f_ctl_stat);
> > >
> > > + /* Ensure the descriptor config is visible before setting the tx
> > > + * pointer.
> > > + */
> > > + smp_wmb();
> > > +
> >
> > Shouldn't these be paired with smp_rmb() on the reader side?
>
> (Not near the code right now) I *think* the reader already has them
> where it matters but I might have overlooked something when I quickly
> checked the other day.
Do we need a read barrier at the start of ftgmac100_tx_complete_packet?
pointer = priv->tx_clean_pointer;
<--- here
txdes = &priv->txdes[pointer];
ctl_stat = le32_to_cpu(txdes->txdes0);
if (ctl_stat & FTGMAC100_TXDES0_TXDMA_OWN)
return false;
This was the only spot I could see that might require one.
Cheers,
Joel
