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

[Masahiro Yamada]

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.



-- 
Best Regards
Masahiro Yamada