On Mon 2017-10-23 14:16:40, Linus Walleij wrote:
> On Mon, Oct 23, 2017 at 11:31 AM, Pavel Machek <pavel@ucw.cz> wrote:
> 
> >> > Thinkpad X220... how do I tell if I was using them? I believe so,
> >> > because I uncovered bug in them before.
> >>
> >> You are certainly using bounce buffers.  What does lspci -knn show?
> >
> > Here is the output:
> > 0d:00.0 System peripheral [0880]: Ricoh Co Ltd PCIe SDXC/MMC Host Controller [1180:e823] (rev 07)
> >         Subsystem: Lenovo Device [17aa:21da]
> >         Kernel driver in use: sdhci-pci
> 
> So that is a Ricoh driver, one of the few that was supposed to benefit
> from bounce buffers.
> 
> Except that if you actually turned it on:
> > [10994.302196] kworker/2:1: page allocation failure: order:4,
> so it doesn't have enough memory to use these bounce buffers
> anyway.

Well, look at archives: driver failed completely when allocation failed. 

> I'm now feel it was the right thing to delete them.

Which means I may have been geting benefit -- when it worked. I
believe solution is to allocate at driver probing time.

(OTOH ... SPI is slow compared to rest of the system, right? Where
does the benefit come from?)

									Pavel



-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html