Add a module parameter to allow the user to enable 64-bit DMA support in EHCI, which has been forcibly disabled since 2003 - see: http://www.mail-archive.com/linux-usb-devel@xxxxxxxxxxxxxxxxxxxxx/msg17230.html At that time the comment was "it'd only matter on a few big Intel boxes anyway", however the situation is much different today when many new machines have 4GB or more of RAM and IOMMU/SWIOTLB are thus needlessly required for USB transfers. For now, the support remains disabled by default and is controlled by an allow_64bit module parameter. Note that some USB device drivers may require updates to pass the DMA capabilities up to their higher layers to avoid unnecessary IOMMU or bounce- buffer use (i.e. networking layer NETIF_F_HIGHDMA). Some of these checks were disabled by the patch listed above, and more may be required again today. However, those previous checks were done incorrectly using dma_supported, which checks to see whether a device's DMA mask can be validly set to a given mask, not whether its previously set mask will accomodate the mask passed in. Signed-off-by: Robert Hancock <hancockrwd@xxxxxxxxx> diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c index 1ec3857..f527e15 100644 --- a/drivers/usb/host/ehci-hcd.c +++ b/drivers/usb/host/ehci-hcd.c @@ -101,6 +101,10 @@ static int ignore_oc = 0; module_param (ignore_oc, bool, S_IRUGO); MODULE_PARM_DESC (ignore_oc, "ignore bogus hardware overcurrent indications"); +static int allow_64bit; +module_param(allow_64bit, bool, S_IRUGO); +MODULE_PARM_DESC(allow_64bit, "allow 64-bit DMA"); + #define INTR_MASK (STS_IAA | STS_FATAL | STS_PCD | STS_ERR | STS_INT) /*-------------------------------------------------------------------------*/ @@ -644,11 +648,9 @@ static int ehci_run (struct usb_hcd *hcd) hcc_params = ehci_readl(ehci, &ehci->caps->hcc_params); if (HCC_64BIT_ADDR(hcc_params)) { ehci_writel(ehci, 0, &ehci->regs->segment); -#if 0 -// this is deeply broken on almost all architectures - if (!dma_set_mask(hcd->self.controller, DMA_BIT_MASK(64))) + if (allow_64bit && + !dma_set_mask(hcd->self.controller, DMA_BIT_MASK(64))) ehci_info(ehci, "enabled 64bit DMA\n"); -#endif } -- 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
