Hi, On Fri, Jun 07, 2013 at 10:19:23AM -0700, Sarah Sharp wrote: > Adding Felipe. > > Xenia, Felipe is the USB "gadget" maintainer, and also added code for > non-PCI xHCI hosts. Felipe, Xenia is my summer intern through the FOSS > Outreach Program for Women: http://kernelnewbies.org/OPWIntro Hey, cool Sarah :-) Welcome Xenia :-) > Felipe, we're discussing the fact that the xHCI host currently does not > set up 64-bit coherent DMA, so we get 64-bit addresses for USB buffers, > but not xHCI data structures. Xenia has a patch to fix it, which can be > found here: http://marc.info/?l=linux-usb&m=137052855612729&w=2 > > Andy thinks the patch has issues with non-PCI xHCI hosts. Looking at the patch, I don't see why it would have any issues, unless some HW engineer flipped the wrong bits in hcc_params, but that would be a silicon bug anyway. I don't have access to anything to test right now (on vacations, last day :-( ) but I'll see if anyone from TI can help testing that patch. Maybe Kishon can help us out here ? Kishon, could you spend a few minutes testing Xenia's patch on OMAP5 to make sure nothing goes wrong with that platform. Again, I can't see how it would fail. > On Fri, Jun 07, 2013 at 03:00:47PM +0300, Mathias Nyman wrote: > > Andy explained his concern in more detail to me irl. > > > > The beef is that the dma_mask is a pointer while dma_coherent_mask > > is a u64 value in struct device, and dma_set_mask() fails if > > dev->dma_mask doesn't point anywhere. > > > > This is not a problem for PCI enumerated devices because PCI probe > > sets a default 32bit mask and makes the dma_mask of all new PCI > > devices point to this value. > > > > For non-pci enumerated devices the device dma_mask may be NULL and > > dma_set_mask() may fail even if dma is supported on the host > > machine. > > > > for example ehci-platform.c solves this by adding: > > > > if (!dev->dev.dma_mask) > > dev->dev.dma_mask = &dev->dev.coherent_dma_mask; > > if (!dev->dev.coherent_dma_mask) > > dev->dev.coherent_dma_mask = DMA_BIT_MASK(32); > > So it sounds like xhci_plat_setup() in xhci-plat.c needs to do something > similar before it calls xhci_gen_setup(). Felipe, do you agree? (now, after reading the whole thing...) I'll agree with that :) > It's funny that the code worked before. Perhaps setting the dma_mask > pointer should be a separate patch for stable? sounds like a good plan to me :-) -- balbi
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