Re: OHCI_BE_FRAME_NO_SHIFT question

Dale Farnsworth wrote:
> On Fri, Oct 05, 2007 at 07:31:33PM +0000, Valentine Barshak wrote:
>> drivers/usb/host/ohci.h:
>>
>> /* HCCA frame number is 16 bits, but is accessed as 32 bits since not all
>>   * hardware handles 16 bit reads.  That creates a different confusion on
>>   * some big-endian SOC implementations.  Same thing happens with PSW 
>> access.
>>   *
>>   * FIXME: Deal with that as a runtime quirk when STB03xxx is ported over
>>   * to arch/powerpc
>>   */
>>
>> #ifdef CONFIG_STB03xxx
>> #define OHCI_BE_FRAME_NO_SHIFT	16
>> #else
>> #define OHCI_BE_FRAME_NO_SHIFT	0
>> #endif
>>
>>
>> Shouldn't we #define OHCI_BE_FRAME_NO_SHIFT	16 for all big endian 
>> platforms?
> 
> No.  OHCI_BE_FRAME_NO_SHIFT is needed to differentiate between
> the big endian sytems that put the frame number in the low 16
> bits and those big endian systems that put the frame number in
> the high 16 bits of that 32-bit field.

OK, thanks.
I've just never worked with those big endian platforms which
do not need this shift.
IIRC, according to OHCI specs, frame number is a 16-bit value and is 
padded with 2 zero bytes, as opposed to 32-bit value. Since it's a 
16-bit value, all be platforms should still have it in the first 2 bytes 
(need the OHCI_BE_FRAME_NO_SHIFT).

> 
>> (At least STB03xxx, 440EP/EPx should have it.)
> 
> Probably.  Each SOC ohci implementation has to be individually
> tested to see how they interpreted the ohci specification.
> 
> -Dale


-------------------------------------------------------------------------
This SF.net email is sponsored by: Splunk Inc.
Still grepping through log files to find problems?  Stop.
Now Search log events and configuration files using AJAX and a browser.
Download your FREE copy of Splunk now >> http://get.splunk.com/
_______________________________________________
[email protected]
To unsubscribe, use the last form field at:
https://lists.sourceforge.net/lists/listinfo/linux-usb-devel