On Thursday 22 October 2015 08:34:53 Appana Durga Kedareswara Rao wrote:
> > On Thursday 22 October 2015 10:16:02 Kedareswara rao Appana wrote:
> > > The driver only supports memory-mapped I/O [by ioremap()], so
> > > readl/writel is actually the right thing to do, IMO.
> > > During the validation of this driver or IP on ARM 64-bit processor
> > > while sending lot of packets observed that the tx packet drop with
> > > iowrite Putting the barriers for each tx fifo register write fixes
> > > this issue Instead of barriers using writel also fixed this issue.
> > >
> > > Signed-off-by: Kedareswara rao Appana <appa...@xilinx.com>
> >
> > The two should really do the same thing: iowrite32() is just a static
> > inline calling
> > writel() on both ARM32 and ARM64. On which kernel version did you observe
> > the
> > difference? It's possible that an older version used CONFIG_GENERIC_IOMAP,
> > which made this slightly more expensive.
>
> I observed this issue with the 4.0.0 kernel version
Is it possible that you have nonstandard patches on your kernel? If so, can
you send a diff against the mainline version?
I don't see CONFIG_GENERIC_IOMAP in 4.0.0, and writel() definitely has the
necessary barriers on arm64, the same way that iowrite() does.
> > If there are barriers that you want to get rid of for performance reasons,
> > you
> > should use writel_relaxed(), but be careful to synchronize them correctly
> > with
> > regard to DMA. It should be fine in this driver, as it does not perform any
> > DMA,
> > but be aware that there is no big-endian version of
> > writel_relaxed() at the moment.
>
> There is no DMA in CAN for this IP.
Ok, good.
Arnd
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
