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

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On Sun, Aug 6, 2023 at 1:48 PM Ladislav Michl <oss-lists@xxxxxxxxx> 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@xxxxxxxxxx>
Date:   Mon Jan 29 00:44:53 2018 +0100

    mmc: sdhci: Implement an SDHCI-specific bounce buffer

?

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

Yours,
Linus Walleij




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