[REGRESSION 4.10] dw_mmc: failures on Rockchip rk3288 veyron boards

Ulf Hansson ulf.hansson at linaro.org
Thu Apr 13 00:17:21 PDT 2017

On 12 April 2017 at 18:12, Doug Anderson <dianders at google.com> wrote:
> Shawn
> On Tue, Apr 11, 2017 at 5:54 PM, Shawn Lin <shawn.lin at rock-chips.com> wrote:
>>> This doesn't surprise me at all.  What surprises me, though, is that
>>> nobody else seems to be able to reproduce this.
>>> On veyron, WiFi is connected via SDIO.  For good speed, it uses SDIO
>>> Interrupts.  See this bit in the device tree:
>>>   cap-sdio-irq;
>> all of *my* boards are using side-band interrupt, so there are no
>> "cap-sdio-irq".
> They are all using side-band interrupt?  What WiFi device do you have connected?
> If you're truly using a side-band interrupt using the dedicated SDIO
> interrupt pin on your SoC, I'm pretty sure you still need to define
> cap-sdio-irq in order for things to work properly.  If you don't do
> that, you'll get "polling mode" for SDIO Interrupts.  See
> sdio_irq_thread() where you can see that the kernel will poll your
> device every 10 ms if MMC_CAP_SDIO_IRQ isn't set.

In these cases I would expect the WIFI driver to deal with the SDIO
IRQ itself and not requesting it via calling sdio_claim_irq(). Because
of this, there should be no polling performed by the sdio_irq_thread.

> Maybe you should try defining cap-sdio-irq and see if you get a big
> performance boost?

No, that seems like a bad idea. I think it would rather add overhead -
decreasing performance. Likely it will also make us wake up the mmc
host from its low power state, when when it actually isn't needed.

Kind regards

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