Re: [PATCH 1/2] mmc: mmci: Drop re-read of MMCISTATUS for busy status

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On Wed, 17 Jul 2019 at 12:16, Jean Nicolas GRAUX
<jean-nicolas.graux@xxxxxx> wrote:
>
> Hello Ulf, all,
>
> For testing purpose, I cherry-picked your patch on top of a 4.19.30 basis.
> (I apologize as it's a bit old. I miss time to do a rebase on current
> linux-next right now.)

No worries about the old kernel, for this change, I think it should be
suufient good as base.

>
> Unfortunately, I got a kernel crash applying it :(

Huh.

Is it crashing because it fails to mount the rootfs on the SD/MMC card?

>
> As you may know, ST sta1295/sta1385 SoC embeds the same pl08x variant
> than one in U8500.
> So It looks like double-checking again mmci status to make sure busy
> flag is still set
> just before proceeding for busy end is required in our case.

Yeah, actually I have a u8500 on my desk now, so I will also test the
patch to see what goes on. Didn't have the time to do it earlier.

My guess is that, at the point when we received the IRQ for a command
that has been sent, and then reading the MMCISTATUS register in
mmci_irq(), the card has not yet started to signal busy on DAT1 and
hence the busy status bit isn't set yet. This leads to that we will
never enable the busy end mask, but just completing the request
directly.

Anyway, let me check and see if I can confirm it.

>
> Regards.
> Jean-Nicolas.

Thanks a lot for helping out testing and reporting the problem!

[...]

Kind regards
Uffe



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