Re: [PATCH 2/3] USB: ehci: add workaround for Synopsys HC bug

[Gabor Juhos <juhosg@openwrt.org>]

2011.04.11. 20:53 keltezéssel, Alan Stern írta:
> On Sun, 10 Apr 2011, Gabor Juhos wrote:
> 
>> A Synopsys USB core used in various SoCs has a bug which might cause
>> that the host controller not issuing ping.
>>
>> When software uses the Doorbell mechanism to remove queue heads, the
>> host controller still has references to the removed queue head even
>> after indicating an Interrupt on Async Advance. This happens if the last
>> executed queue head's Next Link queue head is removed.
>>
>> Consequences of the defect:
>> The Host controller fetches the removed queue head, using memory that
>> would otherwise be deallocated.This results in incorrect transactions on
>> both the USB and system memory. This may result in undefined behavior.
> 
>> --- a/drivers/usb/host/ehci-q.c
>> +++ b/drivers/usb/host/ehci-q.c
>> @@ -1183,6 +1183,9 @@ static void end_unlink_async (struct ehci_hcd *ehci)
>>  		ehci->reclaim = NULL;
>>  		start_unlink_async (ehci, next);
>>  	}
>> +
>> +	if (ehci->has_synopsys_hc_bug)
>> +		writel((u32)ehci->async->qh_dma, &ehci->regs->async_next);
>>  }
> 
> This should be ehci_writel(ehci, ...).

You are right, I will change that.

Thanks,
Gabor