Messages in this thread | | | Date | Wed, 7 Sep 2022 09:27:14 +0100 | Subject | Re: [RFC PATCH v3 3/7] iommu/arm-smmu-v3: support ops registration for CDX bus | From | Robin Murphy <> |
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On 2022-09-07 04:17, Gupta, Nipun wrote: > [AMD Official Use Only - General] > > > >> -----Original Message----- >> From: Saravana Kannan <saravanak@google.com> >> Sent: Wednesday, September 7, 2022 5:41 AM >> To: Gupta, Nipun <Nipun.Gupta@amd.com> >> Cc: robh+dt@kernel.org; krzysztof.kozlowski+dt@linaro.org; >> gregkh@linuxfoundation.org; rafael@kernel.org; eric.auger@redhat.com; >> alex.williamson@redhat.com; cohuck@redhat.com; Gupta, Puneet (DCG-ENG) >> <puneet.gupta@amd.com>; song.bao.hua@hisilicon.com; >> mchehab+huawei@kernel.org; maz@kernel.org; f.fainelli@gmail.com; >> jeffrey.l.hugo@gmail.com; Michael.Srba@seznam.cz; mani@kernel.org; >> yishaih@nvidia.com; jgg@ziepe.ca; jgg@nvidia.com; robin.murphy@arm.com; >> will@kernel.org; joro@8bytes.org; masahiroy@kernel.org; >> ndesaulniers@google.com; linux-arm-kernel@lists.infradead.org; linux- >> kbuild@vger.kernel.org; linux-kernel@vger.kernel.org; >> devicetree@vger.kernel.org; kvm@vger.kernel.org; okaya@kernel.org; Anand, >> Harpreet <harpreet.anand@amd.com>; Agarwal, Nikhil >> <nikhil.agarwal@amd.com>; Simek, Michal <michal.simek@amd.com>; >> Radovanovic, Aleksandar <aleksandar.radovanovic@amd.com>; git (AMD-Xilinx) >> <git@amd.com> >> Subject: Re: [RFC PATCH v3 3/7] iommu/arm-smmu-v3: support ops registration >> for CDX bus >> >> [CAUTION: External Email] >> >> On Tue, Sep 6, 2022 at 6:48 AM Nipun Gupta <nipun.gupta@amd.com> wrote: >>> >>> With new CDX bus supported for AMD FPGA devices on ARM >>> platform, the bus requires registration for the SMMU v3 >>> driver. >>> >>> Signed-off-by: Nipun Gupta <nipun.gupta@amd.com> >>> --- >>> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 16 ++++++++++++++-- >>> 1 file changed, 14 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c >> b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c >>> index d32b02336411..8ec9f2baf12d 100644 >>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c >>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c >>> @@ -29,6 +29,7 @@ >>> #include <linux/platform_device.h> >>> >>> #include <linux/amba/bus.h> >>> +#include <linux/cdx/cdx_bus.h> >>> >>> #include "arm-smmu-v3.h" >>> #include "../../iommu-sva-lib.h" >>> @@ -3690,16 +3691,27 @@ static int arm_smmu_set_bus_ops(struct >> iommu_ops *ops) >>> if (err) >>> goto err_reset_pci_ops; >>> } >>> +#endif >>> +#ifdef CONFIG_CDX_BUS >>> + if (cdx_bus_type.iommu_ops != ops) { >>> + err = bus_set_iommu(&cdx_bus_type, ops); >>> + if (err) >>> + goto err_reset_amba_ops; >>> + } >> >> I'm not an expert on IOMMUs, so apologies if the question is stupid. >> >> Why does the CDX bus need special treatment here (like PCI) when there >> are so many other busses (eg: I2C, SPI, etc) that don't need any >> changes here? > > AFAIU, the devices on I2C/SPI does not use SMMU. Apart from PCI/AMBA, > FSL-MC is another similar bus (on SMMUv2) which uses SMMU ops. > > The devices here are behind SMMU. Robin can kindly correct or add > more here from SMMU perspective.
Indeed, there is no need to describe and handle how DMA may or may not be translated for I2C/SPI/USB/etc. because they are not DMA-capable buses (in those cases the relevant bus *controller* often does DMA, but it does that for itself as the platform/PCI/etc. device it is).
Note that I have a series pending[1] that will make this patch a whole lot simpler.
Thanks, Robin.
[1] https://lore.kernel.org/linux-iommu/cover.1660572783.git.robin.murphy@arm.com/T/#t
> > Thanks, > Nipun > >> >> -Saravana >> >>> #endif >>> if (platform_bus_type.iommu_ops != ops) { >>> err = bus_set_iommu(&platform_bus_type, ops); >>> if (err) >>> - goto err_reset_amba_ops; >>> + goto err_reset_cdx_ops; >>> } >>> >>> return 0; >>> >>> -err_reset_amba_ops: >>> +err_reset_cdx_ops: >>> +#ifdef CONFIG_CDX_BUS >>> + bus_set_iommu(&cdx_bus_type, NULL); >>> +#endif >>> +err_reset_amba_ops: __maybe_unused; >>> #ifdef CONFIG_ARM_AMBA >>> bus_set_iommu(&amba_bustype, NULL); >>> #endif >>> -- >>> 2.25.1 >>>
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