[U-Boot] [PATCH 2/2] ehci-hcd.c, musb_core, usb.h: Add USB_DMA_MINALIGN define for cache alignment

[Tom Rini]

On Sun, Jul 8, 2012 at 11:51 AM, Marek Vasut <marex at denx.de> wrote:
> Dear Ilya Yanok,
>
>> Hi Marek,
>>
>> On Sun, Jul 8, 2012 at 7:08 AM, Marek Vasut <marex at denx.de> wrote:
>>
>> [...]
>>
>> diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
>>
>> > index 04300be..5199560 100644
>> > --- a/drivers/usb/host/ehci-hcd.c
>> > +++ b/drivers/usb/host/ehci-hcd.c
>> > @@ -34,7 +34,10 @@ struct ehci_hccr *hccr;      /* R/O registers, not
>> > need for volatile */
>> >
>> >  volatile struct ehci_hcor *hcor;
>> >
>> >  static uint16_t portreset;
>> >
>> > -static struct QH qh_list __attribute__((aligned(32)));
>> > +DEFINE_CACHE_ALIGN_BUFFER(struct QH, qh_list, 1);
>>
>> This will align on ARCH_DMA_MINALIGN, not USB_DMA_MINALIGN. In case of
>> ARCH_DMA_MINALIGN < 32 we will loose the 32-byte alignment required by USB
>> spec.
>
> That's true -- maybe we should create ALLOC_ALIGN_BUFFER() and
> ALLOC_CACHE_ALIGN_BUFFER() to be a special case of it ?

Lets think.  USB says "32byte min".  Do we have other buses today that
apply similar constraints?  If so, we should probably go about
abstracting into a __ALIGN_FOO(size, what) and do a general one and a
USB one that does 32 or cachline.  If it's just USB that might be
overkill however...

-- 
Tom