| Message ID | 20160427135859.GC20646@e104818-lin.cambridge.arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wednesday 27 April 2016 14:59:00 Catalin Marinas wrote: > > I would be in favour of a dma_inherit() function as well. We could hack > something up in the arch code (like below) but I would rather prefer an > explicit dma_inherit() call by drivers creating such devices. > > diff --git a/arch/arm64/include/asm/dma-mapping.h b/arch/arm64/include/asm/dma-mapping.h > index ba437f090a74..ea6fb9b0e8fa 100644 > --- a/arch/arm64/include/asm/dma-mapping.h > +++ b/arch/arm64/include/asm/dma-mapping.h > @@ -29,8 +29,11 @@ extern struct dma_map_ops dummy_dma_ops; > > static inline struct dma_map_ops *__generic_dma_ops(struct device *dev) > { > - if (dev && dev->archdata.dma_ops) > - return dev->archdata.dma_ops; > + while (dev) { > + if (dev->archdata.dma_ops) > + return dev->archdata.dma_ops; > + dev = dev->parent; > + } I think this would be a very bad idea: we don't want to have random devices be able to perform DMA just because their parent devices have been set up that way. Arnd
On 04/27/2016 04:59 PM, Catalin Marinas wrote: > On Wed, Apr 27, 2016 at 08:41:06AM +0300, Felipe Balbi wrote: >> Grygorii Strashko <grygorii.strashko@ti.com> writes: >>> On 04/26/2016 09:17 AM, Felipe Balbi wrote: >>>> Grygorii Strashko <grygorii.strashko@ti.com> writes: >>>>> Now not all DMA paremters configured properly for "xhci-hcd" platform >>>>> device which is created manually. For example: dma_pfn_offset, dam_ops >>>>> and iommu configuration will not corresponds "dwc3" devices >>>>> configuration. As result, this will cause problems like wrong DMA >>>>> addresses translation on platforms with LPAE enabled like Keystone 2. >>>>> >>>>> When platform is using DT boot mode the DMA configuration will be >>>>> parsed and applied from DT, so, to fix this issue, reuse >>>>> of_dma_configure() API and retrieve DMA configuartion for "xhci-hcd" >>>>> from DWC3 device node. >>>> >>>> patch is incomplete. You left out non-DT users which might suffer from >>>> the same problem. >>> >>> Honestly, I don't know how to fix it gracefully for non-DT case. >>> I can update commit message to mention that this is fix for DT case only. >> >> no, that won't do :-) There are other users for this driver and they are >> all "out-of-compliance" when it comes to DMA usage. Apparently, the >> desired behavior is to pass correct device to DMA API which the gadget >> side is already doing (see below). For the host side, the fix has to be >> more involved. >> >> Frankly, I'd prefer that DMA setup could be inherited from parent >> device, then it wouldn't really matter and a bunch of this could be >> simplified. Some sort of dma_inherit(struct device *dev, struct device >> *parent) would go a long way, IMHO. > > I would be in favour of a dma_inherit() function as well. We could hack > something up in the arch code (like below) but I would rather prefer an > explicit dma_inherit() call by drivers creating such devices. > > diff --git a/arch/arm64/include/asm/dma-mapping.h b/arch/arm64/include/asm/dma-mapping.h > index ba437f090a74..ea6fb9b0e8fa 100644 > --- a/arch/arm64/include/asm/dma-mapping.h > +++ b/arch/arm64/include/asm/dma-mapping.h > @@ -29,8 +29,11 @@ extern struct dma_map_ops dummy_dma_ops; > > static inline struct dma_map_ops *__generic_dma_ops(struct device *dev) > { > - if (dev && dev->archdata.dma_ops) > - return dev->archdata.dma_ops; > + while (dev) { > + if (dev->archdata.dma_ops) > + return dev->archdata.dma_ops; > + dev = dev->parent; > + } > > /* > * We expect no ISA devices, and all other DMA masters are expected to > It's no enough to W/A just dma_ops :( dma_inherit()... FYI: http://www.spinics.net/lists/arm-kernel/msg384012.html Maybe you'll be able to find the way to make it acceptable.
On Wed, Apr 27, 2016 at 04:11:17PM +0200, Arnd Bergmann wrote: > On Wednesday 27 April 2016 14:59:00 Catalin Marinas wrote: > > > > I would be in favour of a dma_inherit() function as well. We could hack > > something up in the arch code (like below) but I would rather prefer an > > explicit dma_inherit() call by drivers creating such devices. > > > > diff --git a/arch/arm64/include/asm/dma-mapping.h b/arch/arm64/include/asm/dma-mapping.h > > index ba437f090a74..ea6fb9b0e8fa 100644 > > --- a/arch/arm64/include/asm/dma-mapping.h > > +++ b/arch/arm64/include/asm/dma-mapping.h > > @@ -29,8 +29,11 @@ extern struct dma_map_ops dummy_dma_ops; > > > > static inline struct dma_map_ops *__generic_dma_ops(struct device *dev) > > { > > - if (dev && dev->archdata.dma_ops) > > - return dev->archdata.dma_ops; > > + while (dev) { > > + if (dev->archdata.dma_ops) > > + return dev->archdata.dma_ops; > > + dev = dev->parent; > > + } > > I think this would be a very bad idea: we don't want to have random > devices be able to perform DMA just because their parent devices > have been set up that way. I agree, it's a big hack. It would be nice to have a simpler way to do this in driver code rather than explicitly calling of_dma_configure/arch_setup_dma_ops as per the original patch in this thread.
On Wednesday 27 April 2016 16:50:19 Catalin Marinas wrote: > On Wed, Apr 27, 2016 at 04:11:17PM +0200, Arnd Bergmann wrote: > > On Wednesday 27 April 2016 14:59:00 Catalin Marinas wrote: > > > > > > I would be in favour of a dma_inherit() function as well. We could hack > > > something up in the arch code (like below) but I would rather prefer an > > > explicit dma_inherit() call by drivers creating such devices. > > > > > > diff --git a/arch/arm64/include/asm/dma-mapping.h b/arch/arm64/include/asm/dma-mapping.h > > > index ba437f090a74..ea6fb9b0e8fa 100644 > > > --- a/arch/arm64/include/asm/dma-mapping.h > > > +++ b/arch/arm64/include/asm/dma-mapping.h > > > @@ -29,8 +29,11 @@ extern struct dma_map_ops dummy_dma_ops; > > > > > > static inline struct dma_map_ops *__generic_dma_ops(struct device *dev) > > > { > > > - if (dev && dev->archdata.dma_ops) > > > - return dev->archdata.dma_ops; > > > + while (dev) { > > > + if (dev->archdata.dma_ops) > > > + return dev->archdata.dma_ops; > > > + dev = dev->parent; > > > + } > > > > I think this would be a very bad idea: we don't want to have random > > devices be able to perform DMA just because their parent devices > > have been set up that way. > > I agree, it's a big hack. It would be nice to have a simpler way to do > this in driver code rather than explicitly calling > of_dma_configure/arch_setup_dma_ops as per the original patch in this > thread. > I haven't followed the entire discussion, but what's wrong with passing around a pointer to a 'struct device *hwdev' that represents the physical device that does the DMA? Arnd
diff --git a/arch/arm64/include/asm/dma-mapping.h b/arch/arm64/include/asm/dma-mapping.h index ba437f090a74..ea6fb9b0e8fa 100644 --- a/arch/arm64/include/asm/dma-mapping.h +++ b/arch/arm64/include/asm/dma-mapping.h @@ -29,8 +29,11 @@ extern struct dma_map_ops dummy_dma_ops; static inline struct dma_map_ops *__generic_dma_ops(struct device *dev) { - if (dev && dev->archdata.dma_ops) - return dev->archdata.dma_ops; + while (dev) { + if (dev->archdata.dma_ops) + return dev->archdata.dma_ops; + dev = dev->parent; + } /* * We expect no ISA devices, and all other DMA masters are expected to