[Letux-kernel] USB sometimes not working

[gatecat]

On Wed, 2021-06-09 at 20:39 +0200, H. Nikolaus Schaller wrote:
> Hi,
> can you please copy to Tony and Andreas and the letux mailing list?
> 
> > Am 09.06.2021 um 19:37 schrieb gatecat <gatecat at ds0.me>:
> > 
> > The main source of USB unreliability I've seen was the hub chip, which
> > takes HSIC from the OMAP and provides the various downstream USB ports.
> > 
> > In particular, I think there was an ordering sensitivity between the
> > initialisation/reset of the hub chip that the kernel driver did out-of-
> > band via I2C/GPIO and the actual USB probing of the hub chip (perhaps
> > because HSIC doesn't deal with a device dropping off the bus, as it
> > does when the hub is reset as well as conventional USB).
> 
> 
> Yes, that is right. I remember that the chip was initially a little flaky but
> was stable for years after
> fixing device trees and overall setup.
> 
> One issue is AFAIR the sequence of reset and i2c.
> 
> The driver can handle reset of the chip but the driver is only loaded if the
> chip responds
> to i2c. AFAIR i2c stops working while in reset state (but I may be wrong and
> the issue
> was slightly different).
> 

Hopefully, this shouldn't happen because the driver brings the chip out of reset
before trying to talk to it over I²C...

> > 
> > I did attempt to improve things with a U-boot patch: 
> >
> https://dev.pyra-handheld.com/kernel/pyra-uboot/-/commit/6cfcca4bfb30716d807f9e2148e6c7b1d644847e
> > 
> > This patch kept the hub in reset until the kernel initialised it, so it
> > didn't appear as a USB device due to being brought out of reset by U-
> > boot; be probed as a USB device by the kernel; then be reset by the
> > kernel hub driver but not re-probed again as a USB device.
> 
> 
> Hm. Does this work at all? AFAIR if the chip is in reset by U-Boot it won't
> respond to
> i2c and the driver is not probed/loaded.
> 
> > 
> > But evidently, this might not be an entire solution after all.
> 
> 
> But be part of a better understanding.
> 
> BR and thanks,
> Nikolaus
> 
> > 
> > Best
> > 
> > gatecat
> > 
> > On Wed, 2021-06-09 at 12:31 +0200, Michael Mrozek wrote:
> > > Hi,
> > > 
> > > sometimes on our OS, the USB ports (as well as the modem) don't work.
> > > Not even a mouse or a similar low-power device works in that case.
> > > 
> > > The hardware should be fine, as IF it works after booting up, it works
> > > totally reliably.
> > > 
> > > I've attached a dmesg output from a user of the boot process when USB
> > > does NOT work.
> > > 
> > > I've also asked him to send a dmesg after he plugs in a device, so we
> > > can see what error USB produces.
> > > 
> > > But there are already a few interesting error messages in the dmesg.
> > > It seems the USB bus is found.. but produces an error.
> > > What's error -110 ?
> > > 
> > > Any idea how to debug this further?
> > > 
> > > AFAIR this effect changes based on the U-Boot / MLO setup you use. I
> > > remember that I tried various U-Boot / MLO combinations when starting
> > > the mass production - and one ALWAYS had a failing USB.
> > > Didn't test that thoroughly, so take it with a grain of salt.
> > > But maybe some initialization parameters in the board file or similar
> > > are off?
> > > 
> > > 
> > > [7.084037] ehci-omap 4a064c00.ehci: EHCI Host Controller
> > > [7.100253] ehci-omap 4a064c00.ehci: new USB bus registered, assigned
> > > bus number 1
> > > [7.114047] ehci-omap 4a064c00.ehci: irq 106, io mem 0x4a064c00
> > > [7.154177] ehci-omap 4a064c00.ehci: USB 2.0 started, EHCI 1.00
> > > [7.170718] usb usb1: New USB device found, idVendor=1d6b,
> > > idProduct=0002, bcdDevice= 5.06
> > > [7.183576] usb usb1: New USB device strings: Mfr=3, Product=2,
> > > SerialNumber=1
> > > [7.195528] usb usb1: Product: EHCI Host Controller
> > > [7.204562] usb usb1: Manufacturer: Linux 5.6.19-daveiii-pyradef-aufs
> > > ehci_hcd
> > > [7.216372] usb usb1: SerialNumber: 4a064c00.ehci
> > > [7.225588] hub 1-0:1.0: USB hub found
> > > [7.233218] hub 1-0:1.0: 3 ports detected
> > > [7.604098] usb 1-2: new high-speed USB device number 2 using ehci-omap
> > > [7.706183] ehci-omap 4a064c00.ehci: port 2 reset error -110
> > > [16.474154] usb usb1-port2: Cannot enable. Maybe the USB cable is bad?
> > > [16.489352] usb usb1-port2: attempt power cycle
> > > 
> > > 
> > > 
> > > 
> > > _______________________________________________
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> > > http://pyra-handheld.com/cgi-bin/mailman/listinfo/kernel
> > 
> > 
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> 

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