Messages in this thread | | | Date | Thu, 12 Mar 2020 11:58:30 +0530 | From | Sai Prakash Ranjan <> | Subject | Re: [PATCH 0/3] Request direct mapping for modem firmware subdevice |
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Hi Robin,
On 2020-03-10 22:14, Robin Murphy wrote: > On 10/03/2020 4:23 pm, Joerg Roedel wrote: >> On Tue, Mar 10, 2020 at 07:30:50PM +0530, Sibi Sankar wrote: >>> The accesses are initiated by the firmware >>> and they access modem reserved regions. >>> However as explained in ^^ any accesses >>> outside the region will result in a violation >>> and is controlled through XPUs (protection units). >> >> Okay, this sounds like a case for arm_smmu_get_resv_region(). It >> should >> return an entry for the reserved memory region the firmware needs to >> access, so that generic iommu can setup this mapping. >> >> Note that it should return that entry only for your device, not for >> all >> devices. Maybe there is a property in DT or IORT you can set to >> transport this information into the arm-smmu driver. >> >> This is pretty similar to RMRR mapping on the Intel VT-d IOMMU or >> Unity-mapped ranges in the AMD-Vi IOMMU. > > Yup, a way to describe boot-time memory regions in IORT is in the > process of being specced out; the first attempt at an equivalent for > DT is here: > > https://lore.kernel.org/linux-iommu/20191209150748.2471814-1-thierry.reding@gmail.com/ > > If that's not enough and the SMMU still needs to treat certain Stream > IDs specially because they may be untranslatable (due to having direct > access to memory as a side-channel), then that should be handled in > the SoC-specific corner of the SMMU driver, not delegated to > individual endpoint drivers. >
Are you talking about this one for SoC specific change - https://lore.kernel.org/patchwork/patch/1183530/
Thanks, Sai
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