[U-Boot] [PATCH 4/4] USB:gadget:designware Fix memory nonalignment issue

[Mike Frysinger <vapier@gentoo.org>]

On Tuesday 06 March 2012 04:51:57 Marek Vasut wrote:
> > On 3/5/2012 11:51 PM, Marek Vasut wrote:
> > > Amit Virdi wrote:
> > >> While receiving packets from FIFO sometimes the buffer provided was
> > >> nonaligned. Fix this by taking a temporary aligned buffer and then
> > >> copying the content to nonaligned buffer.
> > >> 
> > >> --- a/drivers/usb/gadget/designware_udc.c
> > >> +++ b/drivers/usb/gadget/designware_udc.c
> > >> @@ -202,6 +202,7 @@ static int usbgetpckfromfifo(int epNum, u8 *bufp,
> > >> u32 len) u32 i, nw, nb;
> > >> 
> > >>   	u32 *wrdp;
> > >>   	u8 *bytp;
> > >> 
> > >> +	u32 tmp[128];
> > >> 
> > >>   	if (readl(&udc_regs_p->dev_stat)&  DEV_STAT_RXFIFO_EMPTY)
> > >>   	
> > >>   		return -1;
> > >> 
> > >> @@ -209,7 +210,12 @@ static int usbgetpckfromfifo(int epNum, u8 *bufp,
> > >> u32 len) nw = len / sizeof(u32);
> > >> 
> > >>   	nb = len % sizeof(u32);
> > >> 
> > >> -	wrdp = (u32 *)bufp;
> > >> +	/* use tmp buf if bufp is not word aligned */
> > >> +	if ((int)bufp&  0x3)
> > >> +		wrdp = (u32 *)&tmp[0];
> > >> +	else
> > >> +		wrdp = (u32 *)bufp;
> > >> +
> > >> 
> > >>   	for (i = 0; i<  nw; i++) {
> > >>   	
> > >>   		writel(readl(fifo_ptr), wrdp);
> > >>   		wrdp++;
> > >> 
> > >> @@ -223,6 +229,13 @@ static int usbgetpckfromfifo(int epNum, u8 *bufp,
> > >> u32 len) }
> > >> 
> > >>   	readl(&outep_regs_p[epNum].write_done);
> > >> 
> > >> +	/* copy back tmp buffer to bufp if bufp is not word aligned */
> > >> +	if ((int)bufp&  0x3) {
> > >> +		bytp = (u8 *)&tmp[0];
> > >> +		for (i = 0; i<  len; i++)
> > >> +			bufp[i] = bytp[i];
> > >> +	}
> > >> +
> > >> 
> > >>   	return 0;
> > >>   
> > >>   }
> > > 
> > > This addresses EHCI cache problem, that's why you need bounce buffer,
> > > right?
> > 
> > No. The problem was we were copying data word-by-word to a non-word
> > aligned memory in the USB gadget. So, this is different from the USB
> > host controller issue.
> 
> I see ... why isn't buffer aligned by the usb stack then?

because it might not be a requirement higher up.  i.e. it's dealing with a 
data byte stream.  forcing all higher layers to use 32bit alignment because 
this host controller requires 32bit alignment in its FIFOs is incorrect.
-mike
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