From mboxrd@z Thu Jan  1 00:00:00 1970
From: linux@arm.linux.org.uk (Russell King - ARM Linux)
Date: Tue, 16 Feb 2010 08:44:42 +0000
Subject: USB mass storage and ARM cache coherency
In-Reply-To: <EAF47CD23C76F840A9E7FCE10091EFAB02C3CF7D50@dbde02.ent.ti.com>
References: <20100208065519.GE1290@ucw.cz>
	<1265622676.4020.19.camel@pc1117.cambridge.arm.com>
	<20100208105209.GA31671@atrey.karlin.mff.cuni.cz>
	<1265628483.4020.63.camel@pc1117.cambridge.arm.com>
	<EAF47CD23C76F840A9E7FCE10091EFAB02C3CF7D50@dbde02.ent.ti.com>
Message-ID: <20100216084442.GA3212@n2100.arm.linux.org.uk>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Tue, Feb 16, 2010 at 01:27:53PM +0530, Shilimkar, Santosh wrote:
> Continuing on the USB issue w.r.t cache coherency, the usb host
> code is violating the buffer ownership rules of streaming APIs from
> dma and non-dma transfers point if view.
> 
> We have a below temporary patch to get around the issue and probably it
> needs to be fixed in the right way in the stack because some controllers
> may not have PIO option even for control transfers. (e.g. Synopsis EHCI
> controller)

        if (usb_endpoint_xfer_control(&urb->ep->desc)
            && !(urb->transfer_flags & URB_NO_SETUP_DMA_MAP)) {
                if (hcd->self.uses_dma) {		<=================
                        urb->setup_dma = dma_map_single(
                                        hcd->self.controller,
                                        urb->setup_packet,
                                        sizeof(struct usb_ctrlrequest),
                                        DMA_TO_DEVICE);

struct usb_hcd *usb_create_hcd (const struct hc_driver *driver,
                struct device *dev, const char *bus_name)
{
...
        hcd->self.uses_dma = (dev->dma_mask != NULL);

Is it easier to make sure that PIO devices don't have dev->dma_mask set?