The goal of the Generic Kernel Image (GKI) effort is to have a common kernel image that works across multiple Android devices. This involves generating a kernel image that has core features integrated into it, while SoC specific functionality can be added to the kernel for the device as a module.
Along with modularizing IOMMU drivers, this also means building the io-pgtable code as modules, which allows for SoC vendors to only include the io-pgtable implementations that they use. For example, GKI for arm64 must include support for both the IOMMU ARM LPAE/V7S formats at the moment. Having the code for both formats as modules allows SoC vendors to only provide the page table format that they use, along with their IOMMU driver.
The patches are split into 4 parts:
1) Modularizing io-pgtable-arm[-v7s].c, while leaving the io-pgtable.c code as part of the core kernel, requires removing the references to the ARM LPAE and ARM V7S io-pgtable init functions, and using a dynamic method for formats to register their io-pgtable init functions.
2) Taking references to the io-pgtable format drivers to ensure that they cannot be unloaded while in use.
3) Adding pre MODULE_SOFTDEP() dependencies to drivers in the kernel that are tristate, and invoke [alloc/free]_io_pgtable_ops(). This makes it so that the io-pgtable format drivers are loaded before the driver that needs them.
4) Changing the Kconfig options for the ARM LPAE nad ARM V7S to tristate and allowing the io-pgtable code to be enabled without having to select either page table format. The reason for doing this is so that a kernel can be built, such that it only provides the interface for io-pgtable formats to be registered as modules, as would be the case for the GKI.
Thanks, Isaac
Isaac J. Manjarres (7): iommu/io-pgtable: Introduce dynamic io-pgtable format registration iommu/io-pgtable: Add refcounting for io-pgtable format modules iommu/arm-smmu: Add dependency on io-pgtable format modules iommu/arm-smmu-v3: Add dependency on io-pgtable-arm format module drm/msm: Add dependency on io-pgtable-arm format module drm/panfrost: Add dependency on io-pgtable-arm format module iommu/io-pgtable-arm: Allow building modular io-pgtable formats
drivers/gpu/drm/msm/msm_drv.c | 1 + drivers/gpu/drm/panfrost/panfrost_drv.c | 1 + drivers/iommu/Kconfig | 11 +-- drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 1 + drivers/iommu/arm/arm-smmu/arm-smmu.c | 1 + drivers/iommu/io-pgtable-arm-v7s.c | 36 +++++++++- drivers/iommu/io-pgtable-arm.c | 104 +++++++++++++++++++++------- drivers/iommu/io-pgtable.c | 54 ++++++++++----- include/linux/io-pgtable.h | 52 +++++++++----- 9 files changed, 196 insertions(+), 65 deletions(-)