On Wed, May 08, 2013 at 01:42:11AM +0200, Arnd Bergmann wrote:
> On Wednesday 08 May 2013, Greg Kroah-Hartman wrote:
> > On Tue, May 07, 2013 at 04:53:52PM -0600, Stephen Warren wrote:
> > > From: Stephen Warren <swarren@xxxxxxxxxx>
>
> > > Suggested-by: Arnd Bergmann <arnd@xxxxxxxx>
> > > Signed-off-by: Stephen Warren <swarren@xxxxxxxxxx>
> >
> > So this needs to go in for 3.10, right? Any older kernels as well? If
> > so, which ones?
>
> The fix should definitely go into 3.10, but I'd suggest waiting with
> the backport for a couple of -rc releases to avoid possible regressions.
> We know that the current code is broken, but few people fully understand
> what is going on with coherent_dma_mask, so it might cause new problems
> in combination with some other unknown bug, and I don't see this as
> urgent: none of the ARM defconfigs build this driver as a loadable
> module and there is no bug in the built-in case. For some reason, only
> the ARM back-end drivers are broken.
>
> The first occurence was apparently in 3.3, but only in ehci-tegra.c,
> while the other drivers subsequently copied the bug.
I've already suggested this approach:
diff --git a/arch/arm/include/asm/device.h b/arch/arm/include/asm/device.h
index dc662fc..51bb740 100644
--- a/arch/arm/include/asm/device.h
+++ b/arch/arm/include/asm/device.h
@@ -22,6 +22,7 @@ struct dev_archdata {
struct omap_device;
struct pdev_archdata {
+ u64 dma_mask;
#ifdef CONFIG_ARCH_OMAP
struct omap_device *od;
#endif
And then we can have dev->dma_mask pointed at that instead, which fully
eliminates any possible problems of things like dma_set_mask() interfering
with dma_set_coherent_mask().
Even better - because this is a common problem - would be to make 'dma_mask'
be a member of struct platform_device so that all arches can sort this
out once and for all (correction: generic code/drivers can in an arch-
independent way.) IOW:
diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
index 9abf1db..121c74c 100644
--- a/include/linux/platform_device.h
+++ b/include/linux/platform_device.h
@@ -26,6 +26,7 @@ struct platform_device {
struct device dev;
u32 num_resources;
struct resource *resource;
+ u64 dma_mask;
const struct platform_device_id *id_entry;
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