[U-Boot] [PATCH v2] usb: fix usb_stor_read/write on DM

[Marek Vasut]

On 07/19/2017 05:38 PM, Masahiro Yamada wrote:
> 2017-07-15 21:57 GMT+09:00 Marek Vasut <marex at denx.de>:
>> On 07/15/2017 01:30 AM, Benoît Thébaudeau wrote:
>>> On Sat, Jul 15, 2017 at 12:06 AM, Marek Vasut <marex at denx.de> wrote:
>>>> On 07/14/2017 11:46 PM, Benoît Thébaudeau wrote:
>>>>> On Fri, Jul 14, 2017 at 1:50 PM, Marek Vasut <marex at denx.de> wrote:
>>>>>> On 07/14/2017 01:03 PM, Masahiro Yamada wrote:
>>>>>>> 2017-07-14 19:07 GMT+09:00 Marek Vasut <marex at denx.de>:
>>>>>>>> On 07/14/2017 04:31 AM, Masahiro Yamada wrote:
>>>>>>>>> Prior to DM, we could not enable different types of USB controllers
>>>>>>>>> at the same time.  DM was supposed to loosen the limitation.  It is
>>>>>>>>> true that we can compile drivers, but they do not work.
>>>>>>>>>
>>>>>>>>> For example, if EHCI is enabled, xHCI fails as follows:
>>>>>>>>>
>>>>>>>>>   => usb read 82000000 0 2000
>>>>>>>>>
>>>>>>>>>   USB read: device 0 block # 0, count 8192 ... WARN halted endpoint, queueing URB anyway.
>>>>>>>>>   Unexpected XHCI event TRB, skipping... (3fb54010 00000001 13000000 01008401)
>>>>>>>>>   BUG: failure at drivers/usb/host/xhci-ring.c:489/abort_td()!
>>>>>>>>>   BUG!
>>>>>>>>>   ### ERROR ### Please RESET the board ###
>>>>>>>>>
>>>>>>>>> The cause of the error seems the following code:
>>>>>>>>>
>>>>>>>>>   #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.
>>>>>>>>>    */
>>>>>>>>>   #define USB_MAX_XFER_BLK    65535
>>>>>>>>>   #else
>>>>>>>>>   #define USB_MAX_XFER_BLK    20
>>>>>>>>>   #endif
>>>>>>>>>
>>>>>>>>> To fix the problem, choose the chunk size at run-time for CONFIG_BLK.
>>>>>>>>
>>>>>>>> What happens if CONFIG_BLK is not set ?
>>>>>>>
>>>>>>> USB_MAX_XFER_BLK is chosen.
>>>>>>
>>>>>> And can we fix that even for non-CONFIG_BLK ?
>>>>>>
>>>>>>>> Why is it 20 for XHCI anyway ?
>>>>>>>
>>>>>>> You are the maintainer.
>>>>>>> (I hope) you have better knowledge with this.
>>>>>>
>>>>>> Heh, way to deflect the question. I seem to remember some discussion
>>>>>> about the DMA (?) limitation on XHCI, but I'd have to dig through the ML
>>>>>> archives myself.
>>>>>>
>>>>>>> Looks like the following commit was picked up by you.
>>>>>>
>>>>>> 5 years ago, way before DM was what it is today .
>>>>>
>>>>> And even way before the introduction of XHCI into U-Boot, which means
>>>>> that this 20 was targeting OHCI or proprietary HCDs, not XHCI.
>>>>> USB_MAX_READ_BLK was already set to 20 in the initial revision of
>>>>> usb_storage.c. As I said in the commit message, this 20 was certainly
>>>>> not optimal for these non-EHCI HCDs, but it restored the previous
>>>>> (i.e. pre-5dd95cf) behavior for these HCDs instead of using the 5 * 4
>>>>> KiB code, which was specific to ehci-hcd.c at that time. Without
>>>>> knowing the rationale for the legacy 20 blocks, the safest approach
>>>>> for non-EHCI HCDs was to use this value in order to avoid breaking a
>>>>> platform or something. Looking at ohci-hcd.c, it limits the transfer
>>>>> size to (N_URB_TD - 2) * 4 KiB, with N_URB_TD set to 48, so the
>>>>> maximum number of transfers would depend on the MSC block size.
>>>>> dwc2.c, isp116x-hcd.c, r8a66597-hcd.c, and sl811-hcd.c do not seem to
>>>>> have any limit caused by these drivers. The limit with the current
>>>>> XHCI code seems to be 64 * 64 KiB. So, nowadays, USB_MAX_XFER_BLK
>>>>> could be set to 65535 for all HCDs but OHCI and XHCI, which require
>>>>> specific rules depending on the MSC block size.
>>>>
>>>> For whatever reason, something tells me that setting the block size to
>>>> 64k for XHCI broke things, but I cannot locate the thread. But there's
>>>> something in the back of my head ...
>>>
>>> Indeed: according to what I said above, USB_MAX_XFER_BLK cannot be set
>>> to 65535 for XHCI. With an MSC block size of blksz = 512 bytes /
>>> block, USB_MAX_XFER_BLK can be set to at most 1 segment *
>>> (TRBS_PER_SEGMENT = 64 TRBs / segment) * (TRB_MAX_BUFF_SIZE = 65536
>>> bytes / TRB) / blksz = 8192 blocks for XHCI. And for OHCI, the limit
>>> is (N_URB_TD - 2 = 46 TDs) * (4096 bytes / TD) / blksz = 368 blocks.
>>> The buffer alignment may also have to be taken into account to adjust
>>> these values, which would require a USB_MAX_XFER_BLK(host_if, start,
>>> blksz) macro or function. USB_MAX_XFER_BLK can however be set to 65535
>>> regardless of blksz for all the other HCDs (i.e. EHCI, dwc2.c,
>>> isp116x-hcd.c, r8a66597-hcd.c, and sl811-hcd.c).
>>
>> That's probably what I was looking for, thanks.
>>
> 
> 
> So, how shall we handle this?
> 
> If somebody can fix this in a correct way,
> I am happy to hand over this.

Any way to fix it for !CONFIG_BLK ?

-- 
Best regards,
Marek Vasut