[PATCH] usb: ehci: Fix "EHCI timed out on TD - token=XXXX" error on ehci-hcd

[Lukasz Majewski]

Hi Marek,

> On 2/26/20 12:29 PM, Lukasz Majewski wrote:
> > This patch aims to improve robustness of 'usb' command operation on
> > the ehci-hcd IP block as it ports to contemporary U-Boot the patch
> > described and provided in [1] (originally applicable to U-Boot
> > 2016.05).
> > 
> > According to the fix author - "rayvt" (from [1]):  
> 
> [...]
> 
> > diff --git a/common/usb_storage.c b/common/usb_storage.c
> > index 097b6729c1..48c8c2ae64 100644
> > --- a/common/usb_storage.c
> > +++ b/common/usb_storage.c
> > @@ -111,6 +111,18 @@ int usb_stor_get_info(struct usb_device *dev,
> > struct us_data *us, struct blk_desc *dev_desc);
> >  int usb_storage_probe(struct usb_device *dev, unsigned int ifnum,
> >  		      struct us_data *ss);
> > +
> > +#ifdef CONFIG_USB_EHCI_HCD
> > +	/*
> > +	 * The U-Boot EHCI driver can handle any transfer length
> > as long as
> > +	 * there is enough free heap space left, but the SCSI
> > READ(10) and
> > +	 * WRITE(10) commands are limited to 65535 blocks.
> > +	 */
> > +int usb_max_xfer_blk = 4096;
> > +#else
> > +int usb_max_xfer_blk = 20;
> > +#endif  
> 
> This all looks horribly wrong and exactly what
> 7d6fd7f0ba71cd93d94079132f958d9630f27a89 and
> 02b0e1a36c5bc20174299312556ec4e266872bd680 fixed properly.
> 
> All those "dynamic reduction of transfer size" attempts are
> nonsensical, the real solution (sadly) is to reduce the transfer size
> to cater for the most limited devices and profile/fix the remaining
> delays in the USB stack (which should have already been done, see the
> commits above). This is also what the Linux USB stack does.
> 
> What is the problem you are trying to solve here ?

As it was stated in the commit message:

On TPC70 (i.MX6Q) once per ~10 times (without this patch):

Bus usb at 2184200: USB EHCI 1.00
scanning bus usb at 2184200 for devices... 2 USB Device(s) found
       scanning usb for storage devices... 1 Storage Device(s) found
EHCI timed out on TD - token=0x1f8c80


The problem is that even with the mentioned fix in:
7d6fd7f0ba71cd93d94079132f958d9630f27a89 from time to time I do see the:

EHCI timed out on TD - token=0x1f8c80

error. The same issue was already reported by Tom.

The description of the fix written by the original author:
https://forum.doozan.com/read.php?3,35295,35295#msg-35295

states that the reduction of the transfer is done just for "spin
up"/"detection" of the pen drive. The issue is that not all pen drive
disks are able to be properly detected in the first place.



Last but not least - the mainline is still broken. The "token=0x1f8c80"
errors pops up from time to time. However, after applying the approach
from this fix - the error is gone (and pass some acceptance tests).

Best regards,

Lukasz Majewski

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