Date: Wed, 23 Apr 2008 14:08:52 -0700 From: Sam Leffler <sam@freebsd.org> To: Scott Long <scottl@samsco.org> Cc: cvs-src@freebsd.org, src-committers@freebsd.org, cvs-all@freebsd.org, Marius Strobl <marius@alchemy.franken.de> Subject: Re: cvs commit: src/sys/dev/usb ehci.c ohci.c Message-ID: <480FA564.5000008@freebsd.org> In-Reply-To: <480FA4B4.50006@samsco.org> References: <200803201619.m2KGJQr7033985@repoman.freebsd.org> <20080412193358.GA44768@alchemy.franken.de> <20080423203622.GA66545@alchemy.franken.de> <480F9F8B.5050209@freebsd.org> <20080423205943.GG99566@alchemy.franken.de> <480FA4B4.50006@samsco.org>
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Scott Long wrote:
> Marius Strobl wrote:
>> On Wed, Apr 23, 2008 at 01:43:55PM -0700, Sam Leffler wrote:
>>> Marius Strobl wrote:
>>>> On Sat, Apr 12, 2008 at 09:33:58PM +0200, Marius Strobl wrote:
>>>>
>>>>> On Thu, Mar 20, 2008 at 04:19:26PM +0000, Sam Leffler wrote:
>>>>>
>>>>>> sam 2008-03-20 16:19:25 UTC
>>>>>>
>>>>>> FreeBSD src repository
>>>>>>
>>>>>> Modified files:
>>>>>> sys/dev/usb ehci.c ohci.c Log:
>>>>>> Workaround design botch in usb: blindly mixing bus_dma with PIO
>>>>>> does not
>>>>>> work on architectures with a write-back cache as the PIO writes
>>>>>> end up
>>>>>> in the cache which the sync(BUS_DMASYNC_POSTREAD) in
>>>>>> usb_transfer_complete
>>>>>> then discards; compensate in the xfer methods that do PIO by
>>>>>> pushing the
>>>>>> writes out of the cache before usb_transfer_complete is called.
>>>>>>
>>>>>> This fixes USB on xscale and likely other places.
>>>>>>
>>>>>> Sponsored by: hobnob
>>>>>> Reviewed by: cognet, imp
>>>>>> MFC after: 1 month
>>>>>>
>>>>>> Revision Changes Path
>>>>>> 1.62 +16 -0 src/sys/dev/usb/ehci.c
>>>>>> 1.171 +16 -0 src/sys/dev/usb/ohci.c
>>>>>>
>>>>> This causes a crash during boot on sparc64. Looks like map is still
>>>>> NULL at that point.
>>>>>
>>>>>
>>>> Are you ok with the change below or would that also prevent
>>>> your kludge from taking effect?
>>>>
>>>> Marius
>>>>
>>>> Index: ehci.c
>>>> ===================================================================
>>>> RCS file: /usr/data/bsd/cvs/fbsd/src/sys/dev/usb/ehci.c,v
>>>> retrieving revision 1.62
>>>> diff -u -r1.62 ehci.c
>>>> --- ehci.c 20 Mar 2008 16:19:25 -0000 1.62
>>>> +++ ehci.c 23 Apr 2008 20:23:58 -0000
>>>> @@ -664,6 +664,8 @@
>>>> usbd_pipe_handle pipe = xfer->pipe;
>>>> bus_dma_tag_t tag = pipe->device->bus->buffer_dmatag;
>>>> struct usb_dma_mapping *dmap = &xfer->dmamap;
>>>> + if (dmap->map == NULL)
>>>> + return;
>>>> bus_dmamap_sync(tag, dmap->map, BUS_DMASYNC_PREWRITE);
>>>> }
>>>>
>>>> Index: ohci.c
>>>> ===================================================================
>>>> RCS file: /usr/data/bsd/cvs/fbsd/src/sys/dev/usb/ohci.c,v
>>>> retrieving revision 1.171
>>>> diff -u -r1.171 ohci.c
>>>> --- ohci.c 20 Mar 2008 16:19:25 -0000 1.171
>>>> +++ ohci.c 21 Apr 2008 19:13:54 -0000
>>>> @@ -1571,6 +1571,8 @@
>>>> usbd_pipe_handle pipe = xfer->pipe;
>>>> bus_dma_tag_t tag = pipe->device->bus->buffer_dmatag;
>>>> struct usb_dma_mapping *dmap = &xfer->dmamap;
>>>> + if (dmap->map == NULL)
>>>> + return;
>>>> bus_dmamap_sync(tag, dmap->map, BUS_DMASYNC_PREWRITE);
>>>> }
>>>>
>>>>
>>>>
>>>>
>>> You have not identified why you don't have a dma map. I don't have
>>> a way to diagnose your problem and so far as I know no other
>>> platform had an issue w/ the change. I suggest you figure out why
>>> your map is not setup instead of adding a hack.
>>>
>>
>> It's because the usb(4) code doesn't create DMA maps for
>> zero-length transfers, see usbd_transfer(). In the case of
>> the backtrace I posted not for usbd_set_address(), which
>> does USETW(req.wLength, 0) so later on size is 0 in
>> usbd_transfer() hence no DMA map. I don't know why your
>> hack doesn't also crash other platforms.
>>
>>
>
> If there's a transfer without a DMA operation, then why is the
> DMA API being used?
>
It should not be; that's the whole crux of the problem. It doesn't have
different "transport methods" to split out PIO from DMA; it just sends
everything through one set of routines. That's why I had to add my kludge.
Sam
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