Hi Shimoda-san,

> > > That also means, for the sys-dmac and Gen2, we then use 512 for the
> > > IOMMU case and 32 (default TMIO value) for the non IOMMU case. My
> > > understanding is that SYS DMAC can handle 512 in both cases. Maybe it
> > > makes sense then to make an incremental patch setting the max_segs value
> > > explicitly to 512 in the sys-dmac driver for Gen2?
> > 
> > I also think SYS DMAC can handle 512 segments. However, I'm not sure
> > it can improve the performance or not though. Anyway, an incremental patch
> > makes sense if needed, I think.
> 
> I measured the performance on R-Car H2 Lager. It seems 512 segments improve
> the sequential input to 5%. May I make an incremental patch on the patch series?
> What do you think?

Cool! I didn't expect that much of a performance improvement. My main
concern was understandable code because there was no "real reason" that
we once use 32 and once 512.

But if it causes even a performance improvement, even better :)

Yes, an incremental patch is a good idea.

Thanks for the work,

   Wolfram