Re: [PATCH] arm64: dts: qcom: sc8280xp: fix PCIe DMA coherency

[Johan Hovold]

On Fri, Nov 25, 2022 at 08:23:36PM +0530, Manivannan Sadhasivam wrote:
> On Fri, Nov 25, 2022 at 03:43:59PM +0100, Johan Hovold wrote:
> > On Fri, Nov 25, 2022 at 07:56:25PM +0530, Manivannan Sadhasivam wrote:
> > > On Thu, Nov 24, 2022 at 03:25:01PM +0100, Johan Hovold wrote:

> > I never claimed it would fix the problem, I explicitly wrote that it
> > made it less likely to occur (to the point where my reproducer no longer
> > triggers).
> 
> > Increasing the buffer sizes to two pages to force CMA allocation also appears
> > to make the problem go away.
> 
> The "go away" part sounded like a claim to me and hence I added the statement.
> But no worries :)

Hopefully it's clear enough if you also read the preceding sentence
(with emphasis added):

  presumably as these queues are small enough to not be allocated using
  CMA which in turn make them *more likely to be cached* (e.g. due to
  accesses to nearby pages through the cacheable linear map).

Johan