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

[Fabio Estevam]

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.

Reviewed-by: Fabio Estevam <festevam@xxxxxxxxx>

Thanks