[RFT PATCH v1 5/5] usb: Handle QT_TOKEN_STATUS_XACTERR error when sending data

Lukasz Majewski
2020-03-23T12:58:34Z

Hi Marek,

> On 3/23/20 8:18 AM, Lukasz Majewski wrote:
> > Hi Marek,
>
> Hi,
>
> >> On 3/22/20 2:00 PM, Lukasz Majewski wrote:
> >>> This code adds check if QT_TOKEN_STATUS_XACTERR error occurred.
> >>> When it is detected the token is reconfigured and transmission is
> >>> retried.
> >>>
> >>> This code is the port to newest U-Boot of the fix from - "rayvt"
> >>> (from [1]).
> >>>
> >>> Links:
> >>> [1] - https://forum.doozan.com/read.php?3,35295,35295#msg-35295
> >>> [2] -
> >>> https://www.dropbox.com/s/nrkrd1no63viuu8/uboot-bodhi-2016.05-timeoutTD.patch?dl=0
> >>>
> >>>
> >>> Signed-off-by: Lukasz Majewski <lukma@denx.de>
> >>> [Unfortunately, the original patch [2] did not contain S-o-B from
> >>> the original author - "rayvt"]
> >>> ---
> >>>
> >>> drivers/usb/host/ehci-hcd.c | 27 ++++++++++++++++++++++++++-
> >>> 1 file changed, 26 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/usb/host/ehci-hcd.c
> >>> b/drivers/usb/host/ehci-hcd.c index 0a77111f80..45eda7ad24 100644
> >>> --- a/drivers/usb/host/ehci-hcd.c
> >>> +++ b/drivers/usb/host/ehci-hcd.c
> >>> @@ -315,6 +315,7 @@ ehci_submit_async(struct usb_device *dev,
> >>> unsigned long pipe, void *buffer, int timeout;
> >>> int ret = 0;
> >>> struct ehci_ctrl *ctrl = ehci_get_ctrl(dev);
> >>> + int trynum;
> >>>
> >>> debug("dev=%p, pipe=%lx, buffer=%p, length=%d, req=%p\n",
> >>> dev, pipe, buffer, length, req);
> >>> @@ -560,6 +561,10 @@ ehci_submit_async(struct usb_device *dev,
> >>> unsigned long pipe, void *buffer,
> >>> ehci_writel(&ctrl->hcor->or_usbsts, (usbsts & 0x3f));
> >>> /* Enable async. schedule. */
> >>> + trynum = 1; /* No more than 2 tries, in case of
> >>> XACTERR. */ +retry_xacterr:;
> >>> + vtd = &qtd[qtd_counter - 1];
> >>> +
> >>> cmd = ehci_readl(&ctrl->hcor->or_usbcmd);
> >>> cmd |= CMD_ASE;
> >>> ehci_writel(&ctrl->hcor->or_usbcmd, cmd);
> >>
> >> Are you sure always retrying the transfer if you get XACTERR is the
> >> right thing to do, even if you get that e.g. on filesystem writes
> >> ?
> >
> > Please correct me if I'm wrong, but this function -
> > ehci_submit_async
> > - doesn't work with filesystem. It just setups proper EHCI
> > descriptor and checks if it was sent with or without errors.
>
> If you're writing into a block device, this function is used. If you
> get XACTERR during the transfer and you retry, is there a chance the
> data get actually written to the device ?

As fair as I can tell this code snippet doesn't touch file systems.

>
> > When the XACTERR happens, proper flag is cleared and the
> > transmission is retried.
>
> What happens to the payload if it's a host-to-device transfer, do the
> data get discarded or do they get written to the storage ?
>

As state above - the resent shall only result is data being to some
in-memory buffer.

Best regards,

Lukasz Majewski

--

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