> -----Original Message----- > From: Oliver Neukum [mailto:oliver@xxxxxxxxxx] > Sent: Tuesday, February 16, 2010 7:53 PM > To: Shilimkar, Santosh > Cc: Russell King - ARM Linux; Catalin Marinas; Pavel Machek; Greg KH; Matthew Dharm; Sergei Shtylyov; > Ming Lei; Sebastian Siewior; linux-usb@xxxxxxxxxxxxxxx; linux-kernel; linux-arm-kernel; Mankad, > Maulik Ojas > Subject: Re: USB mass storage and ARM cache coherency > > Am Dienstag, 16. Februar 2010 15:12:45 schrieb Shilimkar, Santosh: > > > > > I am afraid for these controllers the controller driver must be responsible > > > > > for all DMA and cache issues. Indicating the exact requirements to the > > > > > upper layer would be a battle already lost. > > > > > so the safe choice is not to set has_dma and the generic layer will leave > > > > > the issue to the lower level. > > > > This means don't use dma at all which will almost kill the performance. > > > > > > Why would you be unable to map a buffer in the hcd driver when you know > > > that you'll use DMA? > > Probably it can be. The USB stack has the dma maintenance code at common > > place for all controllers and hence we were just trying to see if there is > > way to handle that way. > > This is true. If you can find a clean way to describe your requirements > to the generic layer, that would be better. The problem is that we must > not end up with a dozen flags. > > 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) { urb->setup_dma = dma_map_single( hcd->self.controller, urb->setup_packet, @@ -1335,7 +1335,7 @@ static void unmap_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) dma_unmap_single(hcd->self.controller, urb->setup_dma, sizeof(struct usb_ctrlrequest), DMA_TO_DEVICE); diff --git a/include/linux/usb.h b/include/linux/usb.h index d7ace1b..ba5b0a2 100644 --- a/include/linux/usb.h +++ b/include/linux/usb.h @@ -329,6 +329,9 @@ struct usb_bus { int busnum; /* Bus number (in order of reg) */ const char *bus_name; /* stable id (PCI slot_name etc) */ u8 uses_dma; /* Does the host controller use DMA? */ + u8 uses_pio_for_control; /* Does the host controller use PIO + * for control tansfers? + */ u8 otg_port; /* 0, or number of OTG/HNP port */ unsigned is_b_host:1; /* true during some HNP roleswitches */ unsigned b_hnp_enable:1; /* OTG: did A-Host enable HNP? */ Regards, Santosh -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
