[U-Boot] [PATCH] zynq-gem: Flush cache before handing RX packet to receive handler

[Stefan Theil]

Hmm good question. I went with flush because that's what's done in the transmit function:

addr = (ulong) ptr;
addr &= ~(ARCH_DMA_MINALIGN - 1);
size = roundup(len, ARCH_DMA_MINALIGN);
flush_dcache_range(addr, addr + size);

addr = (ulong)priv->rxbuffers;
addr &= ~(ARCH_DMA_MINALIGN - 1);
size = roundup((RX_BUF * PKTSIZE_ALIGN), ARCH_DMA_MINALIGN);
flush_dcache_range(addr, addr + size);
barrier();

But since we actually want the uncached data invalidation seems logical. I have to admit though, I don't have much experience with caches. This patch completely fixed my problem... Maybe somebody with a bit more expertise can add their opinion?

Regards,
Stefan

> -----Ursprüngliche Nachricht-----
> Von: Bin Meng [mailto:bmeng.cn at gmail.com]
> Gesendet: Donnerstag, 13. Dezember 2018 14:13
> An: Stefan Theil
> Cc: U-Boot Mailing List
> Betreff: Re: [U-Boot] [PATCH] zynq-gem: Flush cache before handing RX
> packet to receive handler
> 
> On Thu, Dec 13, 2018 at 6:18 PM Stefan Theil <stefan.theil at mixed-mode.de>
> wrote:
> >
> > The cache was only flushed before *transmitting* packets, but not when
> > receiving them, leading to an issue where new packets were handed to
> > the receive handler with old contents in cache. This only happens when
> > a lot of packets are received without sending packages every now and
> > then.
> >
> > Signed-off-by: Stefan Theil <stefan.theil at mixed-mode.de>
> > ---
> >  drivers/net/zynq_gem.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/net/zynq_gem.c b/drivers/net/zynq_gem.c index
> > 9bd79b198a..5825b6dd99 100644
> > --- a/drivers/net/zynq_gem.c
> > +++ b/drivers/net/zynq_gem.c
> > @@ -621,6 +621,9 @@ static int zynq_gem_recv(struct udevice *dev, int
> > flags, uchar **packetp)
> >
> >         *packetp = (uchar *)(uintptr_t)addr;
> >
> > +       flush_dcache_range(addr, addr + roundup(PKTSIZE_ALIGN,
> > + ARCH_DMA_MINALIGN));
> 
> Shouldn't it be invalidate_dcache_range()?
> 
> > +       barrier();
> > +
> >         return frame_len;
> >  }
> >
> 
> Regards,
> Bin