linux-kernel - Re: [PATCH v2 2/2] Revert "usb: dwc3: Don't switch OTG -> peripheral if extcon is present"

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Message-ID: <CAHQ1cqFqKv+J1=Qg5_sDUeKQ=64aSiGJq0pPH+OqEieZDM1Mfg@mail.gmail.com>
Date:   Sat, 15 Oct 2022 12:54:35 -0700
From:   Andrey Smirnov <andrew.smirnov@...il.com>
To:     Ferry Toth <fntoth@...il.com>
Cc:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Felipe Balbi <balbi@...nel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] Revert "usb: dwc3: Don't switch OTG -> peripheral
 if extcon is present"

On Thu, Oct 13, 2022 at 12:35 PM Ferry Toth <fntoth@...il.com> wrote:
>
> <SNIP>
> > My end goal here is to find a way to test vanilla v6.0 with the two
> > patches reverted on your end. I thought that during my testing I saw
> > tusb1210 print those timeout messages during its probe and that
> > disabling the driver worked to break the loop, but I went back to
> > double check and it doesn't work so scratch that idea. Configuring
> > extcon as a built-in breaks host functionality with or without patches
> > on my end, so I'm not sure it could be a path.
> >
> > I won't have time to try things with
> > 0043b-TODO-driver-core-Break-infinite-loop-when-deferred-p.patch until
> > the weekend, meanwhile can you give this diff a try with vanilla (no
> > reverts) v6.0:
> >

OK, got a chance to try things with that patch. Both v6.0 and v6.0
with my patches reverted work the same, my Kingston DataTraveller USB
stick enumerates and works as expected.

> > modified   drivers/phy/ti/phy-tusb1210.c
> > @@ -127,6 +127,7 @@ static int tusb1210_set_mode(struct phy *phy, enum
> > phy_mode mode, int submode)
> >    u8 reg;
> >
> >    ret = tusb1210_ulpi_read(tusb, ULPI_OTG_CTRL, &reg);
> > + WARN_ON(ret < 0);
> >    if (ret < 0)
> >    return ret;
> >
> > @@ -152,7 +153,10 @@ static int tusb1210_set_mode(struct phy *phy,
> > enum phy_mode mode, int submode)
> >    }
> >
> >    tusb->otg_ctrl = reg;
> > - return tusb1210_ulpi_write(tusb, ULPI_OTG_CTRL, reg);
> > + ret = tusb1210_ulpi_write(tusb, ULPI_OTG_CTRL, reg);
> > + WARN_ON(ret < 0);
> > + return ret;
> > +
> >   }
> >
> >   #ifdef CONFIG_POWER_SUPPLY
> >
> > ? I'm curious to see if there's masked errors on your end since dwc3
> > driver doesn't check for those.
> root@...a:~# dmesg | grep -i -E 'warn|assert|error|tusb|dwc3'
> 8250_mid: probe of 0000:00:04.0 failed with error -16
> platform regulatory.0: Direct firmware load for regulatory.db failed
> with error -2
> brcmfmac mmc2:0001:1: Direct firmware load for
> brcm/brcmfmac43340-sdio.Intel Corporation-Merrifield.bin failed with
> error -2
> sof-audio-pci-intel-tng 0000:00:0d.0: error: I/O region is too small.
> sof-audio-pci-intel-tng 0000:00:0d.0: error: failed to probe DSP -19
>
>
> >> This is done through configfs only when the switch is set to device mode.
> > Sure, but can it be disabled? We are looking for unknown variables, so
> > excluding this would be a reasonable thing to do.
> It's not enabled until I flip the switch to device mode.

OK to cut this back and forth short, I think it'd be easier to just
ask you to run what I run. Here's vanilla v6.0 bzImage and initrd
(built with your config + CONFIG_PHY_TUSB1210=y) I tested with
https://drive.google.com/drive/folders/1H28AL1coPPZ2kLTYskDuDdWo-oE7DRPH?usp=sharing
let's see how it behaves on your setup. There's also the U-Boot binary
I use in that folder in case you want to give it a try.

Now on Merrifield dwc3_get_extcon() doesn't do anything but call
extcon_get_extcon_dev() which doesn't touch any hardware or interact
with other drivers, so assuming

> So current v6.0 has: dwc3_get_extcon - dwc3_get_dr_mode - ... -
> dwc3_core_init - .. - dwc3_core_init_mode (not working)
>
> I changed to: dwc3_get_dr_mode - dwc3_get_extcon - .. - dwc3_core_init -
> .. - dwc3_core_init_mode (no change)
>
> Then to: dwc3_get_dr_mode - .. - dwc3_core_init - .. - dwc3_get_extcon -
> dwc3_core_init_mode (works)

still holds(did you double check that with vanilla v6.0?) the only
difference that I can see is execution timings. It seems to me it's
either an extra delay added by execution of  extcon_get_extcon_dev()
(unlikely) or multiple partial probes that include dwc3_core_init()
that change things. You can try to check the latter by adding an
artificial probe deferral point after dwc3_core_init(). Something like
(didn't test this):

modified   drivers/usb/dwc3/core.c
@@ -1860,6 +1860,10 @@ static int dwc3_probe(struct platform_device *pdev)
  goto err3;

  ret = dwc3_core_init(dwc);
+ static int deferral_counter = 0;
+ if (deferral_counter++ < 9) /* I counted 9 deferrals in my testing */
+ ret = -EPROBE_DEFER;
+
  if (ret) {
  dev_err_probe(dev, ret, "failed to initialize core\n");
  goto err4;