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From:   Fabio Estevam <festevam@gmail.com>
Date:   Sat, 4 Nov 2023 19:30:11 -0300
Message-ID: <CAOMZO5DZ7f1dBNy3QidjjdSk9TCExHAF3ZNk1ryyvnooRmipzA@mail.gmail.com>
Subject: Re: [PATCH] arm64: dts: imx8mp: imx8mq: Add parkmode-disable-ss-quirk
 on DWC3
To:     Nathan Rossi <nathan@nathanrossi.com>
Cc:     devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, Nathan Rossi <nathan.rossi@digi.com>,
        Li Jun <jun.li@nxp.com>, Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        NXP Linux Team <linux-imx@nxp.com>
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Hi Nathan,

Thanks for your fix.

On Thu, Nov 2, 2023 at 5:24=E2=80=AFAM Nathan Rossi <nathan@nathanrossi.com=
> wrote:
>
> From: Nathan Rossi <nathan.rossi@digi.com>
>
> 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=3D/dev/sd... of=3D/dev/null bs=3D16) 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 xh=
ci-hcd
>   [13241.015582] sd 2:0:0:0: [sdc] tag#0 UNKNOWN(0x2003) Result: hostbyte=
=3D0x07 driverbyte=3DDRIVER_OK cmd_age=3D0s
>   [13241.025198] sd 2:0:0:0: [sdc] tag#0 CDB: opcode=3D0x28 28 00 00 00 0=
3 e0 00 01 00 00
>   [13241.032949] I/O error, dev sdc, sector 992 op 0x0:(READ) flags 0x807=
00 phys_seg 25 prio class 2
>   [13272.150710] usb 2-1.2: reset SuperSpeed USB device number 4 using xh=
ci-hcd
>   [13272.175469] sd 1:0:0:0: [sdb] tag#0 UNKNOWN(0x2003) Result: hostbyte=
=3D0x03 driverbyte=3DDRIVER_OK cmd_age=3D31s
>   [13272.185365] sd 1:0:0:0: [sdb] tag#0 CDB: opcode=3D0x28 28 00 00 00 0=
3 e0 00 01 00 00
>   [13272.193385] I/O error, dev sdb, sector 992 op 0x0:(READ) flags 0x807=
00 phys_seg 18 prio class 2
>   [13434.846556] xhci-hcd xhci-hcd.0.auto: xHCI host not responding to st=
op endpoint command
>   [13434.854592] xhci-hcd xhci-hcd.0.auto: xHCI host controller not respo=
nding, assume dead
>   [13434.862553] xhci-hcd xhci-hcd.0.auto: HC died; cleaning up
>
> [1] https://github.com/nxp-imx/linux-imx/commit/97a5349d936b08cf301730b59=
e4e8855283f815c
> [2] https://github.com/nxp-imx/linux-imx/commit/b4b5cbc5a12d7c3b920d1d7cb=
a0ada3379e4e42b

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@gmail.com>

Thanks