Re: [net-next] net: ethernet: ravb: Suspend and resume the transmission flow

["Niklas Söderlund" <niklas.soderlund+renesas@ragnatech.se>]

Hi Geert,

On 2026-04-08 09:44:33 +0200, Geert Uytterhoeven wrote:
> Hi Niklas,
> 
> On Tue, 7 Apr 2026 at 20:54, Niklas Söderlund
> <niklas.soderlund+renesas@ragnatech.se> wrote:
> > On 2026-04-07 11:03:38 +0200, Geert Uytterhoeven wrote:
> > > On Wed, 1 Apr 2026 at 20:39, Niklas Söderlund
> > > <niklas.soderlund+renesas@ragnatech.se> wrote:
> > > >
> > > > From: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
> > > >
> > > > The current driver does not follow the latest datasheet and does not
> > > > suspend the flow when stopping DMA and resume it when starting. Update
> > > > the driver to do so.
> > > >
> > > > Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
> > > > [Niklas: Rebase from BSP and reword commit message]
> > > > Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> > >
> > > Thanks for your patch, which is now commit 353d8e7989b6babe ("net:
> > > ethernet: ravb: Suspend and resume the transmission flow") in
> > > linux-next/master net-next.
> > >
> > > > --- a/drivers/net/ethernet/renesas/ravb_main.c
> > > > +++ b/drivers/net/ethernet/renesas/ravb_main.c
> > > > @@ -694,6 +694,9 @@ static int ravb_dmac_init(struct net_device *ndev)
> > > >         const struct ravb_hw_info *info = priv->info;
> > > >         int error;
> > > >
> > > > +       /* Clear transmission suspension */
> > > > +       ravb_modify(ndev, CCC, CCC_DTSR, 0);
> > > > +
> > > >         /* Set CONFIG mode */
> > > >         error = ravb_set_opmode(ndev, CCC_OPC_CONFIG);
> > > >         if (error)
> > > > @@ -1103,6 +1106,12 @@ static int ravb_stop_dma(struct net_device *ndev)
> > > >         if (error)
> > > >                 return error;
> > > >
> > > > +       /* Request for transmission suspension */
> > > > +       ravb_modify(ndev, CCC, CCC_DTSR, CCC_DTSR);
> > > > +       error = ravb_wait(ndev, CSR, CSR_DTS, CSR_DTS);
> > > > +       if (error)
> > > > +               netdev_err(ndev, "failed to stop AXI BUS\n");
> > >
> > > This error message is printed during resume from s2idle or s2ram on
> > > e.g. Salvator-XS and Gray Hawk Single.  Ethernet (nfsroot) still works
> > > fine, though.
> >
> > I was not able to reproduce this on M3N (r8a77965-salvator-xs.dts) nor
> > Sparrow Hawk (r8a779g3-sparrow-hawk.dts). I'm using the following to
> > test, is your test-case different?
> >
> >   # echo enabled > /sys/class/tty/ttySC0/power/wakeup
> >   # echo s2idle > /sys/power/mem_sleep
> >   # echo 0 > /sys/module/printk/parameters/console_suspend
> >   # echo mem > /sys/power/state
> 
> Looks good. Major difference seems to be that I use either Wake-on-LAN
> or gpio-keys wake-up, and I always have WoL enabled for ravb.

WoL was indeed the key.

Having iperf3 blasting traffic to the target made no difference and 
access to URAM is allowed to be suspended and no warning was triggered,
however just enabling WoL and no traffic.

    # ethtool -s end0 wol g

And URAM access will not be suspended and reported active when checking 
DTS in CSR register and this warning will be printed. I will send a 
patch to ignore the check if WoL is enabled (when net-next open), but 
still keep the request to stop URAM access. Nice catch!

> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> -- 
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds

-- 
Kind Regards,
Niklas Söderlund