| Message ID | 1414422568-19103-3-git-send-email-stefano.stabellini@eu.citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, 27 Oct 2014, Stefano Stabellini wrote: > Introduce a boolean flag and an accessor function to check whether a > device is dma_coherent. Set the flag from set_arch_dma_coherent_ops. > > Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> > CC: will.deacon@arm.com Will, Catalin, are you OK with this patch? > arch/arm64/include/asm/device.h | 1 + > arch/arm64/include/asm/dma-mapping.h | 6 ++++++ > 2 files changed, 7 insertions(+) > > diff --git a/arch/arm64/include/asm/device.h b/arch/arm64/include/asm/device.h > index cf98b36..243ef25 100644 > --- a/arch/arm64/include/asm/device.h > +++ b/arch/arm64/include/asm/device.h > @@ -21,6 +21,7 @@ struct dev_archdata { > #ifdef CONFIG_IOMMU_API > void *iommu; /* private IOMMU data */ > #endif > + bool dma_coherent; > }; > > struct pdev_archdata { > diff --git a/arch/arm64/include/asm/dma-mapping.h b/arch/arm64/include/asm/dma-mapping.h > index adeae3f..e213dc4 100644 > --- a/arch/arm64/include/asm/dma-mapping.h > +++ b/arch/arm64/include/asm/dma-mapping.h > @@ -54,11 +54,17 @@ static inline void set_dma_ops(struct device *dev, struct dma_map_ops *ops) > > static inline int set_arch_dma_coherent_ops(struct device *dev) > { > + dev->archdata.dma_coherent = true; > set_dma_ops(dev, &coherent_swiotlb_dma_ops); > return 0; > } > #define set_arch_dma_coherent_ops set_arch_dma_coherent_ops > > +static inline bool is_device_dma_coherent(struct device *dev) > +{ > + return dev->archdata.dma_coherent; > +} > + > #include <asm-generic/dma-mapping-common.h> > > static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr) > -- > 1.7.10.4 >
On Mon, Nov 03, 2014 at 10:46:03AM +0000, Stefano Stabellini wrote: > On Mon, 27 Oct 2014, Stefano Stabellini wrote: > > Introduce a boolean flag and an accessor function to check whether a > > device is dma_coherent. Set the flag from set_arch_dma_coherent_ops. > > > > Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> > > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> > > CC: will.deacon@arm.com > > Will, Catalin, > are you OK with this patch? It would be nicer if the dma_coherent flag didn't have to be duplicated by each architecture in dev_archdata. Is there any reason not to put it in the core code? Will
On Mon, 3 Nov 2014, Will Deacon wrote: > On Mon, Nov 03, 2014 at 10:46:03AM +0000, Stefano Stabellini wrote: > > On Mon, 27 Oct 2014, Stefano Stabellini wrote: > > > Introduce a boolean flag and an accessor function to check whether a > > > device is dma_coherent. Set the flag from set_arch_dma_coherent_ops. > > > > > > Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> > > > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> > > > CC: will.deacon@arm.com > > > > Will, Catalin, > > are you OK with this patch? > > It would be nicer if the dma_coherent flag didn't have to be duplicated by > each architecture in dev_archdata. Is there any reason not to put it in the > core code? Yes, there is a reason for it: if I added a boolean dma_coherent flag in struct device as Catalin initially suggested, what would be the default for each architecture? Where would I set it for arch that don't use device tree? It is not easy. I thought it would be better to introduce is_device_dma_coherent only on the architectures where it certainly makes sense to have it. In fact I checked and arm and arm64 are the only architectures to define set_arch_dma_coherent_ops at the moment. At that point if is_device_dma_coherent becomes arch-specific, it makes sense to store the flag in dev_archdata instead of struct device.
Hi Stefano, On 11/03/2014 01:10 PM, Stefano Stabellini wrote: > On Mon, 3 Nov 2014, Will Deacon wrote: >> On Mon, Nov 03, 2014 at 10:46:03AM +0000, Stefano Stabellini wrote: >>> On Mon, 27 Oct 2014, Stefano Stabellini wrote: >>>> Introduce a boolean flag and an accessor function to check whether a >>>> device is dma_coherent. Set the flag from set_arch_dma_coherent_ops. >>>> >>>> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> >>>> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> >>>> CC: will.deacon@arm.com >>> >>> Will, Catalin, >>> are you OK with this patch? >> >> It would be nicer if the dma_coherent flag didn't have to be duplicated by >> each architecture in dev_archdata. Is there any reason not to put it in the >> core code? > > Yes, there is a reason for it: if I added a boolean dma_coherent flag in > struct device as Catalin initially suggested, what would be the default > for each architecture? Where would I set it for arch that don't use > device tree? It is not easy. > > I thought it would be better to introduce is_device_dma_coherent only on > the architectures where it certainly makes sense to have it. In fact I > checked and arm and arm64 are the only architectures to define > set_arch_dma_coherent_ops at the moment. At that point if > is_device_dma_coherent becomes arch-specific, it makes sense to store > the flag in dev_archdata instead of struct device. The proposition from Will looks reasonable for me too, because there is "small" side-effect of adding such kind of properties to arch-specific data or even to the core device structure. ;( There are some sub-systems in kernel which do not create their devices from DT and instead some host device populates its children devices manually. Now, I know at least two cases: - usb: dwc3 core creates xhci device manually - pci: adds its client devices In such, case DMA configuration have to be propagated from host to child (in our case host device's got DMA configuration from DT), like: dma_set_coherent_mask(&xhci->dev, dwc->dev->coherent_dma_mask); xhci->dev.parent = dwc->dev; xhci->dev.dma_mask = dwc->dev->dma_mask; xhci->dev.dma_parms = dwc->dev->dma_parms; So, once new DMA property is added it has to be propagated from host to child device too. Recently, the new property dma_pfn_offset was introduced in struct device and such kind of problem was observed on keystone 2: - for usb case it was fixed using Platform Bus notifier (xhci - platform device) - for pci - the work is in progress, because solution with PCI Bus notifier was rejected https://lkml.org/lkml/2014/10/10/308. In general, if dma_coherent will belong to struct device then such problems will be possible to fix directly in drivers/subsystems: xhci->dev.dma_coherent = dwc->dev->dma_coherent; But, if it will be arch-specific data then it will be impossible to set it without introducing proper and arch-specific setters/getters functions. Also, as an idea, we are thinking about introducing something like: void dma_apply_parent_cfg(struct device *dev, struct device *parent) which will ensure that all DMA configuration properly copied from parent to children device. Now it should be (as minimum for ARM): dma_mask coherent_dma_mask dma_parms dma_pfn_offset dev_archdata->dma_ops [dma_coherent]? regards, -grygorii
On Tue, 4 Nov 2014, Grygorii Strashko wrote: > Hi Stefano, > > On 11/03/2014 01:10 PM, Stefano Stabellini wrote: > > On Mon, 3 Nov 2014, Will Deacon wrote: > >> On Mon, Nov 03, 2014 at 10:46:03AM +0000, Stefano Stabellini wrote: > >>> On Mon, 27 Oct 2014, Stefano Stabellini wrote: > >>>> Introduce a boolean flag and an accessor function to check whether a > >>>> device is dma_coherent. Set the flag from set_arch_dma_coherent_ops. > >>>> > >>>> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> > >>>> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> > >>>> CC: will.deacon@arm.com > >>> > >>> Will, Catalin, > >>> are you OK with this patch? > >> > >> It would be nicer if the dma_coherent flag didn't have to be duplicated by > >> each architecture in dev_archdata. Is there any reason not to put it in the > >> core code? > > > > Yes, there is a reason for it: if I added a boolean dma_coherent flag in > > struct device as Catalin initially suggested, what would be the default > > for each architecture? Where would I set it for arch that don't use > > device tree? It is not easy. > > > > I thought it would be better to introduce is_device_dma_coherent only on > > the architectures where it certainly makes sense to have it. In fact I > > checked and arm and arm64 are the only architectures to define > > set_arch_dma_coherent_ops at the moment. At that point if > > is_device_dma_coherent becomes arch-specific, it makes sense to store > > the flag in dev_archdata instead of struct device. > > The proposition from Will looks reasonable for me too, because > there is "small" side-effect of adding such kind of properties to > arch-specific data or even to the core device structure. ;( > > There are some sub-systems in kernel which do not create their devices > from DT and instead some host device populates its children devices manually. > Now, I know at least two cases: > - usb: dwc3 core creates xhci device manually > - pci: adds its client devices > > In such, case DMA configuration have to be propagated from host to > child (in our case host device's got DMA configuration from DT), like: > dma_set_coherent_mask(&xhci->dev, dwc->dev->coherent_dma_mask); > > xhci->dev.parent = dwc->dev; > xhci->dev.dma_mask = dwc->dev->dma_mask; > xhci->dev.dma_parms = dwc->dev->dma_parms; > > So, once new DMA property is added it has to be propagated from > host to child device too. > > Recently, the new property dma_pfn_offset was introduced in struct device > and such kind of problem was observed on keystone 2: > - for usb case it was fixed using Platform Bus notifier (xhci - platform device) > - for pci - the work is in progress, because solution with PCI Bus notifier > was rejected https://lkml.org/lkml/2014/10/10/308. > > In general, if dma_coherent will belong to struct device then > such problems will be possible to fix directly in drivers/subsystems: > xhci->dev.dma_coherent = dwc->dev->dma_coherent; > > But, if it will be arch-specific data then it will be impossible to > set it without introducing proper and arch-specific setters/getters functions. > > Also, as an idea, we are thinking about introducing something like: > void dma_apply_parent_cfg(struct device *dev, struct device *parent) > which will ensure that all DMA configuration properly copied from > parent to children device. Now it should be (as minimum for ARM): > dma_mask > coherent_dma_mask > dma_parms > dma_pfn_offset > dev_archdata->dma_ops > [dma_coherent]? I understand your concern but the problem you have goes far beyond a simple dma_coherent flag: what about all the other dev_archdata fields? Aside from dma_ops, on some other architectures there might be other data structrures in dev_archdata that need to be properly initialized from the parent. Your idea of introducing something like dma_apply_parent_cfg is the only solid solution I can see. However I would consider naming it something more generic like init_dev_from_parent to handle other possible configurations (inside or outside dev_archdata) that might have to be initialized from information on the parent device. Regarding the dma_coherent flag, I still prefer this approach because introducing the dma_coherent flag in dev_archdata wouldn't make this issue any worse than already is, but would avoid other problems as mentioned in my previous reply.
diff --git a/arch/arm64/include/asm/device.h b/arch/arm64/include/asm/device.h index cf98b36..243ef25 100644 --- a/arch/arm64/include/asm/device.h +++ b/arch/arm64/include/asm/device.h @@ -21,6 +21,7 @@ struct dev_archdata { #ifdef CONFIG_IOMMU_API void *iommu; /* private IOMMU data */ #endif + bool dma_coherent; }; struct pdev_archdata { diff --git a/arch/arm64/include/asm/dma-mapping.h b/arch/arm64/include/asm/dma-mapping.h index adeae3f..e213dc4 100644 --- a/arch/arm64/include/asm/dma-mapping.h +++ b/arch/arm64/include/asm/dma-mapping.h @@ -54,11 +54,17 @@ static inline void set_dma_ops(struct device *dev, struct dma_map_ops *ops) static inline int set_arch_dma_coherent_ops(struct device *dev) { + dev->archdata.dma_coherent = true; set_dma_ops(dev, &coherent_swiotlb_dma_ops); return 0; } #define set_arch_dma_coherent_ops set_arch_dma_coherent_ops +static inline bool is_device_dma_coherent(struct device *dev) +{ + return dev->archdata.dma_coherent; +} + #include <asm-generic/dma-mapping-common.h> static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)