Re: dwc3-qcom: tx-fifo-resize regression on Poco F1 (sdm845) with v5.15-rc1

[Amit Pundir]

Hi Wesley,

On Tue, 21 Sept 2021 at 02:44, Wesley Cheng <wcheng@xxxxxxxxxxxxxx> wrote:
>
> Hi Amit,
>
> On 9/20/2021 1:45 PM, Amit Pundir wrote:
> > Hi Wesley, All,
> >
> > I see a reboot loop on Xiaomi Pocophone F1 (sdm845) with TX FIFO
> > resize patches which landed in v5.15-rc1. Upstream commit cefdd52fa045
> > "usb: dwc3: dwc3-qcom: Enable tx-fifo-resize property by default" to
> > be specific, which switched on this feature by default.
> >
> > At times the phone crashes into the fastboot mode after the reboot
> > loop, but mostly end up booting to UI after a while. This is what it
> > looks like https://people.linaro.org/~amit.pundir/beryllium-userdebug/PXL_20210920_162749483.mp4.
> >
>
> I believe Android will attempt a number of bootup sequences and if it
> fails, it falls back to fastboot mode.  Are there any available logs you
> might be able to collect to see where the issue is?

It is a stock phone with no UART access, so I can't get early crash
logs unless I'm booted up to adb shell. I can try getting some info
using pstore-ramoops but warm reset support for sdm845 was not
upstreamed when I tried using that the last time.

>
> > PocoF1 does support TX fifo resizing as I can see that in the
> > downstream dts. So maybe it is the tx-fifo-max-num which need to be
> > adjusted for the device? I couldn't find the tx-fifo-max-num
> > equivalent in the downstream tree though
> > https://github.com/MiCode/Xiaomi_Kernel_OpenSource/tree/dipper-q-oss/
> >
>
> I assume that you've already confirmed reverting that change resolves
> the constant reboots?

Yes reverting that change resolves the reboot loop issue. Speaking of
which, since no other platform seem to be running into this issue and
"tx-fifo-max-num" property is apparently not at fault either, is it
reasonable to skip adding "tx-fifo-resize" property for PocoF1 using
of_machine_is_compatible("xiaomi,beryllium") as a workaround?

>
> > Curious if you had any ideas what might be going wrong? For now I'll
> > keep digging around tx-fifo-max-num, but I figured I'd ask just in
> > case it's obvious to you.
> >
>
> The tx-fifo-max-num parameter should still be set to 6 for SDM845, which
> would be the same for more recent targets as well.

Ack.

Regards,
Amit Pundir

>
> Thanks
> Wesley Cheng
>
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