[Letux-kernel] omap_hsmmc RX DMA errors

H. Nikolaus Schaller hns at goldelico.com
Thu Jan 5 20:01:34 CET 2023

Hi Adam,
happy new year!

> Am 05.01.2023 um 18:54 schrieb Adam Ford <aford173 at gmail.com>:
> I am trying to test the 6.0 kernel on an AM3517-EVM, but I am seeing
> some DMA RX errors:
> [    1.730682] omap_hsmmc 4809c000.mmc: RX DMA channel request failed
> [    1.738403] omap_hsmmc 480b4000.mmc: RX DMA channel request failed

I think I remember there was an issue that more an more devices were switched active by default
to use DMA until the 32 channels of an OMAP are filled up. Which subsystem is hit by this
limitation may vary and depends if they are properly disabled on the specific board DTS.

See: https://git.goldelico.com/?p=letux-kernel.git;a=commit;h=048b9bc86b9a080258460c4ab2989660233c4c8c

(I must admit that it is not yet upstreamed).

> I tried changing the omap3.dtsi file to use the newer sdhci-omap
> controller instead of the older hsmmc driver since it has support for
> the omap3.

This would then only be a workaround but not a solution.

> That seemed to fix the issue:
> [    2.141967] omap-dma-engine 48056000.dma-controller: OMAP DMA engine driver
> [    2.183074] mmc1: SDHCI controller on 480b4000.mmc [480b4000.mmc]
> using External DMA
> [    2.184631] mmc0: SDHCI controller on 4809c000.mmc [4809c000.mmc]
> using External DMA
> Would there be an objection if I migrate the OMAP3.dtsi file to the
> newer driver?  I wasn't sure if there was a reason this family was
> being held back from the newer driver.

AFAIR Tony wanted to retire the older driver anyways.

Best regards,

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