Re: (Octeon) MMC performance degradation due to too many requests

[Ladislav Michl <oss-lists@triops.cz>]

On Sun, Aug 06, 2023 at 10:44:21PM +0200, Linus Walleij wrote:
> On Sun, Aug 6, 2023 at 1:48 PM Ladislav Michl <oss-lists@triops.cz> wrote:
> 
> > How do we get there?
> > ff4143ccff31 ("MIPS: Octeon: cavium_octeon_defconfig: Enable Octeon MMC")
> > enabled MMC driver, but left MMC_BLOCK_BOUNCE disabled, although driver
> > performace depends on it.
> 
> Ooops.
> 
> > c3dccb74be28 ("mmc: core: Delete bounce buffer Kconfig option")
> > Added MMC_CAP_NO_BOUNCE_BUFF to the caps, based on assumption it should
> > be there as MMC_BLOCK_BOUNCE is disabled in defconfig
> > de3ee99b097d ("mmc: Delete bounce buffer handling")
> > finally removed all bounce buffer handling as almost nothing needs that.
> >
> > Sadly, 70XX SoC cannot do SG, so it suffers a lot. Strangely enough,
> > above patches are either authored or suggested by Cavium's employees.
> >
> > So, given the number of affected SoC and before cooking driver specific
> > solution, are we sure we indeed do not want some generic one?
> 
> So you are talking about something along the lines of:
> 
> commit bd9b902798ab14d19ca116b10bde581ddff8f905
> Author: Linus Walleij <linus.walleij@linaro.org>
> Date:   Mon Jan 29 00:44:53 2018 +0100
> 
>     mmc: sdhci: Implement an SDHCI-specific bounce buffer
> 
> ?

Yes, this is the exact commit I had in mind :)

> Yeah I guess that if this is needed by more than one driver it
> should be made into a library, or say a piece of code turned on by
> a config option that the dependent drivers select.
> 
> Interested in the job? :D

Interested is not the word I'd use, but yes, I'll give it a try making it
a little more generic solution.

> Yours,
> Linus Walleij

Best reards,
	ladis