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

[Amit Pundir <amit.pundir@linaro.org>]

On Tue, 21 Sept 2021 at 13:00, Wesley Cheng <wcheng@codeaurora.org> wrote:
>
> Hi Amit,
>
> On 9/21/2021 12:04 AM, Amit Pundir wrote:
> > Hi Wesley,
> >
> > On Tue, 21 Sept 2021 at 02:44, Wesley Cheng <wcheng@codeaurora.org> 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.
> >
>
> I see, can we maybe avoid the actual resizing by commenting out the
> following writel() calls, but let the fifo resize logic calculate the EPs?
>
> void dwc3_gadget_clear_tx_fifos(struct dwc3 *dwc)
> {
> ...
>                 /* Don't change TXFRAMNUM on usb31 version */
>                 size = DWC3_IP_IS(DWC3) ? 0 :
>                         dwc3_readl(dwc->regs, DWC3_GTXFIFOSIZ(num >> 1)) &
>                                    DWC31_GTXFIFOSIZ_TXFRAMNUM;
>                 /* Comment the dwc3_writel() */
>                 //dwc3_writel(dwc->regs, DWC3_GTXFIFOSIZ(num >> 1), size);
>
> and
>
> static int dwc3_gadget_resize_tx_fifos(struct dwc3_ep *dep)
> {
> ...
>         /* Comment the dwc3_writel() */
>         //dwc3_writel(dwc->regs, DWC3_GTXFIFOSIZ(dep->number >> 1), fifo_size);
>         dwc->num_ep_resized++;
>
> Those 2 writel() would be the one that actually programs the TXFIFO
> register.  I hope when commented out, no resize should actually happen
> anymore.
>
> With this, hopefully we can get some logs from the device at least :)

I can boot fine with above 2 writel() removed but I don't see EP
counts being printed in the log anywhere and the only relevant
message in dmesg I see is this:

    Duplicate name in dwc3@a600000, renamed to "tx-fifo-resize#1"

which is interesting because I don't see tx-fifo-resize property being
set by any of the upstream sdm845 or relevant dtsi files.


>
> >>
> >>> 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?
> >
>
> Since SDM845 does technically support txfifo resize downstream, let me
> see if I can figure out what is different on this particular device
> after getting the logs.
>
> Thanks
> Wesley Cheng
>
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