From mboxrd@z Thu Jan 1 00:00:00 1970 From: oliver@neukum.org (Oliver Neukum) Date: Wed, 17 Feb 2010 10:10:57 +0100 Subject: USB mass storage and ARM cache coherency In-Reply-To: References: <20100208065519.GE1290@ucw.cz> <201002161522.38467.oliver@neukum.org> Message-ID: <201002171010.57464.oliver@neukum.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Am Mittwoch, 17. Februar 2010 09:55:08 schrieb Shilimkar, Santosh: > > Your original patch however kills ehci, ohci and uhci on some architectures. > > How about below approach? Controller driver can set > "uses_pio_for_control" if it can't do dma for control transfer. > > diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c > index 80995ef..e3eae02 100644 > --- a/drivers/usb/core/hcd.c > +++ b/drivers/usb/core/hcd.c > @@ -1276,7 +1276,7 @@ static int map_urb_for_dma(struct usb_hcd *hcd, struct urb *urb, > > if (usb_endpoint_xfer_control(&urb->ep->desc) > && !(urb->transfer_flags & URB_NO_SETUP_DMA_MAP)) { > - if (hcd->self.uses_dma) { > + if (hcd->self.uses_dma && !hcd->self.uses_pio_for_control) { It is not elegant to describe exceptions. It would be better, if you split up the flag into two flags, called uses_dma_for_ordinary_transfers and uses_dma_for control_transfers. Doing so also makes sure you look at all hcd drivers ;-) And the tests become straightforward. And please add a detailed comment to explain why this differentiation is needed on ARM. Regards Oliver