cvs commit: src/sys/dev/usb ehci.c ohci.c

[Scott Long]

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?

Scott