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SubjectRe: [PATCH v1] usb: host: Implement workaround for Erratum A-007463
On Wed, Sep 20, 2017 at 05:24:41PM +0800, yinbo.zhu@nxp.com wrote:
> From: "yinbo.zhu" <yinbo.zhu@nxp.com>
>
> When a transaction error (defined in Section 4.10.2.3, "USB
> Transaction Error" of the xHCI Specification) occurs on the
> USB, the host controller reports this through a transfer
> event with the completion code "USB Transaction Error". When
> this happens, the endpoint is placed in the Halted state.
> In response, software must issue a Reset Endpoint command to
> transition the endpoint to the Stopped state. In order to
> restart the transfer, the driver can perform either of the
> following:
> • Ring the doorbell again, which restarts the transfer from
> where it stopped, or
> • Issue a Set TR (Transfer Ring) Dequeue Pointer command for
> the endpoint to start the transfer from a different
> Transfer Ring pointer Consider the following scenario:
> 1. The xHCI driver prepares a control transfer read to one
> of the device's control endpoints;
> 2. During the IN data stage, a transaction error occurs on
> the USB, causing a transfer event with the completion
> code "USB Transaction Error";
> 3. The driver issues a Reset Endpoint command;
> 4. The driver rings the doorbell of the control endpoint to
> resume the transfer. In this scenario, the controller
> may reverse the direction of the data stage from IN to OUT.
> Instead of sending an ACK to the endpoint to poll for read
> data, it sends a Data Packet (DP) to the endpoint. It
> fetches the data from the data stage Transfer Request Block
> (TRB) that is being resumed, even though the data buffer is
> setup to receive data and not transmit it.
> NOTE
> This issue occurs only if the transaction error happens during
> an IN data stage. There is no issue if the transaction error
> happens during an OUT data stage.
>
> Impact: When this issue occurs, the device likely responds in
> one of the following ways:
> • The device responds with a STALL because the data stage has
> unexpectedly changed directions. The controller then generates
> a Stall Error transfer event, to which software must issue a
> Reset Endpoint command followed by a Set TR Dequeue Pointer
> command pointing to a new Setup TRB to clear the STALL condition.
> • The device does not respond to the inverted data stage and the
> transaction times out. The controller generates another USB
> Transaction Error transfer event, to which software likely
> performs a USB Reset to the device because it is unresponsive.
> It is not expected that any of these recovery steps will cause
> instability in the system because this recovery is part of a
> standard xHCI driver and could happen regardless of the defect.
> Another possible system-level impact is that the controller
> attempts to read from the memory location pointed at by the Data
> Stage TRB or a Normal TRB chained to it. associated with this
> TRB is intended to be written by the controller, but the
> controller reads from it instead. Normally, this does not cause
> a problem. However, if the system has some type of memory
> protection where this unexpected read is treated as a bus error,
> it may cause the system to become unstable or to crash.
>
> Workaround: If a USB Transaction Error occurs during the IN
> data phase of a control transfer, the driver must use the
> Set TR Dequeue Pointer command to either restart the data
> phase or restart the entire control transfer from the
> Setup phase.
>
> Configs Affected:
> LS1021-20-22A-R1.0, LS1021-20-22A-R2.007463

What does this reference?

Same for the subject: line, I don't know what that means.

> Signed-off-by: yinbo.zhu <yinbo.zhu@nxp.com>
> ---
> arch/arm/boot/dts/ls1021a.dtsi | 1 +
> drivers/usb/dwc3/core.c | 2 ++
> drivers/usb/dwc3/core.h | 2 ++
> drivers/usb/dwc3/host.c | 2 ++
> drivers/usb/host/xhci-plat.c | 3 +++
> drivers/usb/host/xhci-ring.c | 28 +++++++++++++++++++++++-----
> drivers/usb/host/xhci.h | 3 ++-
> 7 files changed, 35 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm/boot/dts/ls1021a.dtsi b/arch/arm/boot/dts/ls1021a.dtsi
> index 7bb9df2c1460..9f76b2b82dce 100644
> --- a/arch/arm/boot/dts/ls1021a.dtsi
> +++ b/arch/arm/boot/dts/ls1021a.dtsi
> @@ -683,6 +683,7 @@
> dr_mode = "host";
> snps,quirk-frame-length-adjustment = <0x20>;
> snps,dis_rxdet_inp3_quirk;
> + snps,quirk_reverse_in_out;

Doesn't that value have to be added to some other DT documentation file?

> - /* Issue a reset endpoint command to clear the host side
> - * halt, followed by a set dequeue command to move the
> - * dequeue pointer past the TD.
> - * The class driver clears the device side halt later.
> + /*
> + * A-007463: After transaction error, controller switches
> + * control transfer data stage from IN to OUT direction.
> */

What does A-007463 refer to?

> --- a/drivers/usb/host/xhci.h
> +++ b/drivers/usb/host/xhci.h
> @@ -1780,7 +1780,7 @@ struct xhci_hcd {
> #define XHCI_STATE_DYING (1 << 0)
> #define XHCI_STATE_HALTED (1 << 1)
> #define XHCI_STATE_REMOVING (1 << 2)
> - unsigned int quirks;
> + u64 quirks;

Why change this to a u64?

thanks,

greg k-h

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