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

[Masahiro Yamada]

2017-07-20 2:33 GMT+09:00 Marek Vasut <marex at denx.de>:
> 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 ?


common/usb_storage.c is sprinkled with ugly #ifdef CONFIG_BLK

IIUC, !CONFIG_BLK code will be removed after migration.

Is it worthwhile to save !CONFIG_BLK case?



-- 
Best Regards
Masahiro Yamada