Re: [PATCH v2] arm64: dts: rockchip: add rk3399 UART DMAs

[Robin Murphy]

On 11/04/2019 13:46, Heiko Stuebner wrote:
> Hi Robin,
>
> Am Samstag, 30. MÃrz 2019, 00:24:16 CEST schrieb Robin Murphy:
> > On 2019-03-27 12:00 pm, Heiko Stuebner wrote:
> > > Hi,
> > >
> > > Am Dienstag, 26. MÃrz 2019, 14:49:16 CET schrieb Katsuhiro Suzuki:
> > > > Hello Robin,
> > > >
> > > > Sorry for inconvenience. Since I don't adhere enabling DMA for UARTs,
> > > > please revert my patch if you need.
> > >
> > > I've dropped the patch from my queue now.
> > >
> > > > BTW, there are DMA properties in RK3328 device-tree like as this patch.
> > > > RK3328 UART DMA could not work correctly too...??
> > >
> > > I remember Rockcihip dma-controllers having issues with burst-sizes
> > > and flushing (there is a no-flushp option in pl330), so it's
> > > possible that all share the same error up to rk3399 and rk3328
> > >
> > > But so far no-one has shouted regarding the rk3328.
> >
> > Let me be the first, then, I guess :)
> >
> > I found an easy way to observe the problem on my 3399, and I've just
> > fired up my 3328 box with a 5.0 distro kernel to find that it behaves
> > the same. Basically just dump a large pile of text into 'less' on the
> > serial console, and scroll through line-by-line - certain lines get
> > dropped except for a few characters at the end.
> >
> > I'll see if I can narrow it down a bit, starting with trying
> > broken-flushp...
>
> did you manage to find time for that test you wanted to do?

Sadly not - I got somewhat distracted by the ethernet thing, and since 
then I've had too much else going on to follow up on any of my 'for fun' 
projects :(

If it helps, from a quick look based on what I can remember off-hand, 
Rockchip UARTs in general have probably been using DMA since 4.19 with 
d8095f94e195 ("dmaengine: add support for reporting pause and resume 
separately").

Robin.