[PATCH v4 0/5] memory: Introduce memory controller mini-framework

Thierry Reding
2020-02-13T16:40:12Z

Hi,

this set of patches adds a new binding that allows device tree nodes to
explicitly define the DMA parent for a given device. This supplements
the existing interconnect bindings and is useful to disambiguate in the
case where a device has multiple paths to system memory. Beyond that it
can also be useful when there aren't any actual interconnect paths that
can be controlled, so in simple cases this can serve as a simpler
variant of interconnect paths.

One other case where this is useful is to describe the relationship
between devices such as the memory controller and an IOMMU, for example.
On Tegra186 and later, the memory controller is programmed with a set of
stream IDs that are to be associated with each memory client. This
programming needs to happen before translations through the IOMMU start,
otherwise the used stream IDs may deviate from the expected values. The
memory-controllers property is used in this case to ensure that the
memory controller driver has been probed (and hence has programmed the
stream ID mappings) before the IOMMU becomes available.

Patch 1 introduces the memory controller bindings, both from the
perspective of the provider and the consumer. Patch 2 makes use of a
memory-controllers property to determine the DMA parent for the purpose
of setting up DMA masks (based on the dma-ranges property of the DMA
parent). Patch 3 introduces a minimalistic framework that is used to
register memory controllers with along with a set of helpers to look up
the memory controller from device tree.

An example of how to register a memory controller is shown in patch 4
for Tegra186 (and later) and finally the ARM SMMU driver is extended to
become a consumer of an (optional) memory controller. As described
above, the goal is to defer probe as long as the memory controller has
not yet programmed the stream ID mappings.

Thierry

Thierry Reding (5):
dt-bindings: Add memory controller bindings
of: Use memory-controllers property for DMA parent
memory: Introduce memory controller mini-framework
memory: tegra186: Register as memory controller
iommu: arm-smmu: Get reference to memory controller

.../bindings/memory-controllers/consumer.yaml | 14 +
.../memory-controllers/memory-controller.yaml | 32 +++
drivers/iommu/arm-smmu.c | 11 +
drivers/iommu/arm-smmu.h | 2 +
drivers/memory/Makefile | 1 +
drivers/memory/core.c | 248 ++++++++++++++++++
drivers/memory/tegra/tegra186.c | 9 +-
drivers/of/address.c | 25 +-
include/linux/memory-controller.h | 34 +++
9 files changed, 366 insertions(+), 10 deletions(-)
create mode 100644 Documentation/devicetree/bindings/memory-controllers/consumer.yaml
create mode 100644 Documentation/devicetree/bindings/memory-controllers/memory-controller.yaml
create mode 100644 drivers/memory/core.c
create mode 100644 include/linux/memory-controller.h