On Sun, Jun 6, 2021, at 11:52, Greg Kroah-Hartman wrote: > On Sun, Jun 06, 2021 at 11:36:29AM +0200, Sven Peter wrote: > > Currently, the dwc3 platform driver does not explicitly ask for > > a DMA mask. This makes it fall back to the default 32-bit mask which > > breaks the driver on systems that only have RAM starting above the > > first 4G like the Apple M1 SoC. > > > > Fix this by using the same logic already present in xhci-plat.c: > > First, try to set a coherent dma mask for 64-bit, and then attempt > > again with a 32-bit mask if this fails. > > > > Signed-off-by: Sven Peter <sven@xxxxxxxxxxxxx> > > --- > > > > I have taken the code directly from the xhci-plat.c driver so > > I think this change should be fairly low risk. > > Unfortunately I only have the Apple M1 to test this on but here > > the driver still works with the iommu enabled which limits the > > address space to 32 bit. It also enables to use this with the iommu > > in bypass mode which requires 64 bit addresses. > > > > I believe this has been working fine so far since the dwc3 driver > > only uses a few very small buffers in host mode which might still > > fit within the first 4G of address space on many devices. The > > majority of DMA buffers are allocated inside the xhci driver which > > will already call dma_set_mask_and_coherent. > > > > Best, > > > > Sven > > > > drivers/usb/dwc3/core.c | 15 +++++++++++++++ > > 1 file changed, 15 insertions(+) > > > > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c > > index b6e53d8212cd..ef6bb6aaffd8 100644 > > --- a/drivers/usb/dwc3/core.c > > +++ b/drivers/usb/dwc3/core.c > > @@ -1545,6 +1545,21 @@ static int dwc3_probe(struct platform_device *pdev) > > > > dwc3_get_properties(dwc); > > > > + /* Try to set 64-bit DMA first */ > > + if (WARN_ON(!dwc->sysdev->dma_mask)) > > This will cause systems to reboot if they have panic-on-warn set. Are > you sure you want that to happen? Probably not :) I'll remove the WARN_ON. thanks, Sven
