Re: [PATCH] arm64: dts: imx8mp: imx8mq: Add parkmode-disable-ss-quirk on DWC3

[Nathan Rossi]

On Sun, 5 Nov 2023 at 08:30, Fabio Estevam <festevam@xxxxxxxxx> wrote:
>
> Hi Nathan,
>
> Thanks for your fix.
>
> On Thu, Nov 2, 2023 at 5:24 AM Nathan Rossi <nathan@xxxxxxxxxxxxxxx> wrote:
> >
> > From: Nathan Rossi <nathan.rossi@xxxxxxxx>
> >
> > The i.MX8MP and i.MX8MQ devices both use the same DWC3 controller and
> > are both affected by a known issue with the controller due to specific
> > behaviour when park mode is enabled in SuperSpeed host mode operation.
> >
> > Under heavy USB traffic from multiple endpoints the controller will
> > sometimes incorrectly process transactions such that some transactions
> > are lost, or the controller may hang when processing transactions. When
> > the controller hangs it does not recover.
> >
> > This issue is documented partially within the linux-imx vendor kernel
> > which references a Synopsys STAR number 9001415732 in commits [1] and
> > additional details in [2]. Those commits provide some additional
> > controller internal implementation specifics around the incorrect
> > behaviour of the SuperSpeed host controller operation when park mode is
> > enabled.
> >
> > The summary of this issue is that the host controller can incorrectly
> > enter/exit park mode such that part of the controller is in a state
> > which behaves as if in park mode even though it is not. In this state
> > the controller incorrectly calculates the number of TRBs available which
> > results in incorrect access of the internal caches causing the overwrite
> > of pending requests in the cache which should have been processed but
> > are ignored. This can cause the controller to drop the requests or hang
> > waiting for the pending state of the dropped requests.
> >
> > The workaround for this issue is to disable park mode for SuperSpeed
> > operation of the controller through the GUCTL1[17] bit. This is already
> > available as a quirk for the DWC3 controller and can be enabled via the
> > 'snps,parkmode-disable-ss-quirk' device tree property.
> >
> > It is possible to replicate this failure on an i.MX8MP EVK with a USB
> > Hub connecting 4 SuperSpeed USB flash drives. Performing continuous
> > small read operations (dd if=/dev/sd... of=/dev/null bs=16) on the block
> > devices will result in device errors initially and will eventually
> > result in the controller hanging.
> >
> >   [13240.896936] xhci-hcd xhci-hcd.0.auto: WARN Event TRB for slot 4 ep 2 with no TDs queued?
> >   [13240.990708] usb 2-1.3: reset SuperSpeed USB device number 5 using xhci-hcd
> >   [13241.015582] sd 2:0:0:0: [sdc] tag#0 UNKNOWN(0x2003) Result: hostbyte=0x07 driverbyte=DRIVER_OK cmd_age=0s
> >   [13241.025198] sd 2:0:0:0: [sdc] tag#0 CDB: opcode=0x28 28 00 00 00 03 e0 00 01 00 00
> >   [13241.032949] I/O error, dev sdc, sector 992 op 0x0:(READ) flags 0x80700 phys_seg 25 prio class 2
> >   [13272.150710] usb 2-1.2: reset SuperSpeed USB device number 4 using xhci-hcd
> >   [13272.175469] sd 1:0:0:0: [sdb] tag#0 UNKNOWN(0x2003) Result: hostbyte=0x03 driverbyte=DRIVER_OK cmd_age=31s
> >   [13272.185365] sd 1:0:0:0: [sdb] tag#0 CDB: opcode=0x28 28 00 00 00 03 e0 00 01 00 00
> >   [13272.193385] I/O error, dev sdb, sector 992 op 0x0:(READ) flags 0x80700 phys_seg 18 prio class 2
> >   [13434.846556] xhci-hcd xhci-hcd.0.auto: xHCI host not responding to stop endpoint command
> >   [13434.854592] xhci-hcd xhci-hcd.0.auto: xHCI host controller not responding, assume dead
> >   [13434.862553] xhci-hcd xhci-hcd.0.auto: HC died; cleaning up
> >
> > [1] https://github.com/nxp-imx/linux-imx/commit/97a5349d936b08cf301730b59e4e8855283f815c
> > [2] https://github.com/nxp-imx/linux-imx/commit/b4b5cbc5a12d7c3b920d1d7cba0ada3379e4e42b
>
> It is a shame that NXP fixed it only in their vendor tree and kept
> mainline with the issue.
>
> This deserves a Fixes tag so that it can be backported to stable kernels.

The two commits that would need to be applied against would be:

Fixes: fb8587a2c165 ("arm64: dtsi: imx8mp: add usb nodes")
Fixes: ad37549cb5dc ("arm64: dts: imx8mq: add USB nodes")

The imx8mq one is a bit tricky since that commit occurred in the v5.1
kernel which is before the parkmode support was added to the dwc3
driver (added in v5.7, but was backported to stable kernels all the
way to v5.4). However since there is no active stable 5.1-5.3 kernels
this should be fine?

If those commits are the correct Fixes target let me know and I can
resend this change as v2 with the Fixes and your reviewed-by.

Thanks,
Nathan

>
> Reviewed-by: Fabio Estevam <festevam@xxxxxxxxx>
>
> Thanks