[PATCH v2 15/18] dt-bindings: riscv: Describe physical memory regions

[Samuel Holland <samuel.holland@sifive.com>]

Information about physical memory regions is needed by both the kernel
and M-mode firmware. For example, the kernel needs to know about
noncacheable aliases of cacheable memory in order to allocate coherent
memory pages for DMA. M-mode firmware needs to know about those aliases
so it can protect itself from lower-privileged software.

The RISC-V Privileged Architecture delegates the description of Physical
Memory Attributes (PMAs) to the platform. On DT-based platforms, it
makes sense to put this information in the devicetree.

Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
---

Changes in v2:
 - Remove references to Physical Address Width (no longer part of Smmpt)
 - Remove special first entry from the list of physical memory regions
 - Fix compatible string in example

 .../bindings/riscv/physical-memory.yaml       | 91 +++++++++++++++++++
 include/dt-bindings/riscv/physical-memory.h   | 44 +++++++++
 2 files changed, 135 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/riscv/physical-memory.yaml
 create mode 100644 include/dt-bindings/riscv/physical-memory.h

diff --git a/Documentation/devicetree/bindings/riscv/physical-memory.yaml b/Documentation/devicetree/bindings/riscv/physical-memory.yaml
new file mode 100644
index 0000000000000..825b712a9fbae
--- /dev/null
+++ b/Documentation/devicetree/bindings/riscv/physical-memory.yaml
@@ -0,0 +1,91 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/riscv/physical-memory.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: RISC-V Physical Memory Regions
+
+maintainers:
+  - Samuel Holland <samuel.holland@sifive.com>
+
+description:
+  The RISC-V Privileged Architecture defines a number of Physical Memory
+  Attributes (PMAs) which apply to a given region of memory. These include the
+  types of accesses (read, write, execute, LR/SC, and/or AMO) allowed within
+  a region, the supported access widths and alignments, the cacheability and
+  coherence of the region, and whether or not accesses to the region may have
+  side effects.
+
+  Some RISC-V platforms provide multiple physical address mappings for main
+  memory or certain peripherals. Each alias of a region generally has different
+  PMAs (e.g. cacheable vs non-cacheable), which allows software to dynamically
+  select the PMAs for an access by referencing the corresponding alias.
+
+  On DT-based RISC-V platforms, this information is provided by the
+  riscv,physical-memory-regions property of the root node.
+
+properties:
+  $nodename:
+    const: '/'
+
+  riscv,physical-memory-regions:
+    $ref: /schemas/types.yaml#/definitions/uint32-matrix
+    description:
+      Each table entry provides PMAs for a specific physical memory region,
+      which must not overlap with any other table entry.
+    minItems: 1
+    maxItems: 256
+    items:
+      minItems: 4
+      maxItems: 6
+      additionalItems: true
+      items:
+        - description: CPU physical address (#address-cells)
+        - description: >
+            Size (#size-cells). For entry 0, if the size is zero, the size is
+            assumed to be 2^(32 * #size-cells).
+        - description: >
+            Flags describing the most restrictive PMAs for any address within
+            the region.
+
+            The least significant byte indicates the types of accesses allowed
+            for this region. Note that a memory region may support a type of
+            access (e.g. AMOs) even if the CPU does not.
+
+            The next byte describes the cacheability, coherence, idempotency,
+            and ordering PMAs for this region. It also includes a flag to
+            indicate that accesses to a region are unsafe and must be
+            prohibited by software (for example using PMPs or Smmpt).
+
+            The third byte is reserved for future PMAs.
+
+            The most significant byte is the index of the lowest-numbered entry
+            which this entry is an alias of, if any. Aliases need not be the
+            same size, for example if a smaller memory region repeats within a
+            larger alias.
+        - description: Reserved for describing future PMAs
+
+additionalProperties: true
+
+examples:
+  - |
+    #include <dt-bindings/riscv/physical-memory.h>
+
+    / {
+      compatible = "beagle,beaglev-starlight-jh7100-r0", "starfive,jh7100";
+      #address-cells = <2>;
+      #size-cells = <2>;
+
+      riscv,physical-memory-regions =
+          <0x00 0x18000000 0x00 0x00020000 (PMA_RWX | PMA_NONCACHEABLE_MEMORY) 0x0>,
+          <0x00 0x18080000 0x00 0x00020000 (PMA_RWX | PMA_NONCACHEABLE_MEMORY) 0x0>,
+          <0x00 0x41000000 0x00 0x1f000000 (PMA_RWX | PMA_NONCACHEABLE_MEMORY) 0x0>,
+          <0x00 0x61000000 0x00 0x1f000000 (PMA_RWXA | PMA_NONCOHERENT_MEMORY | PMR_ALIAS(3)) 0x0>,
+          <0x00 0x80000000 0x08 0x00000000 (PMA_RWXA | PMA_NONCOHERENT_MEMORY) 0x0>,
+          <0x10 0x00000000 0x08 0x00000000 (PMA_RWX | PMA_NONCACHEABLE_MEMORY | PMR_ALIAS(5)) 0x0>,
+          <0x20 0x00000000 0x10 0x00000000 (PMA_RWX | PMA_NONCACHEABLE_MEMORY) 0x0>,
+          <0x30 0x00000000 0x10 0x00000000 (PMA_RWXA | PMA_NONCOHERENT_MEMORY | PMR_ALIAS(7)) 0x0>;
+    };
+
+...
diff --git a/include/dt-bindings/riscv/physical-memory.h b/include/dt-bindings/riscv/physical-memory.h
new file mode 100644
index 0000000000000..7cb2e58fa8c1c
--- /dev/null
+++ b/include/dt-bindings/riscv/physical-memory.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) */
+
+#ifndef _DT_BINDINGS_RISCV_PHYSICAL_MEMORY_H
+#define _DT_BINDINGS_RISCV_PHYSICAL_MEMORY_H
+
+#define PMA_READ			(1 << 0)
+#define PMA_WRITE			(1 << 1)
+#define PMA_EXECUTE			(1 << 2)
+#define PMA_AMO_MASK			(3 << 4)
+#define PMA_AMO_NONE			(0 << 4)
+#define PMA_AMO_SWAP			(1 << 4)
+#define PMA_AMO_LOGICAL			(2 << 4)
+#define PMA_AMO_ARITHMETIC		(3 << 4)
+#define PMA_RSRV_MASK			(3 << 6)
+#define PMA_RSRV_NONE			(0 << 6)
+#define PMA_RSRV_NON_EVENTUAL		(1 << 6)
+#define PMA_RSRV_EVENTUAL		(2 << 6)
+
+#define PMA_RW				(PMA_READ | PMA_WRITE)
+#define PMA_RWA				(PMA_RW | PMA_AMO_ARITHMETIC | PMA_RSRV_EVENTUAL)
+#define PMA_RWX				(PMA_RW | PMA_EXECUTE)
+#define PMA_RWXA			(PMA_RWA | PMA_EXECUTE)
+
+#define PMA_ORDER_MASK			(3 << 8)
+#define PMA_ORDER_IO_RELAXED		(0 << 8)
+#define PMA_ORDER_IO_STRONG		(1 << 8)
+#define PMA_ORDER_MEMORY		(2 << 8)
+#define PMA_READ_IDEMPOTENT		(1 << 10)
+#define PMA_WRITE_IDEMPOTENT		(1 << 11)
+#define PMA_CACHEABLE			(1 << 12)
+#define PMA_COHERENT			(1 << 13)
+
+#define PMA_UNSAFE			(1 << 15)
+
+#define PMA_IO				(PMA_ORDER_IO_RELAXED)
+#define PMA_NONCACHEABLE_MEMORY		(PMA_ORDER_MEMORY | PMA_READ_IDEMPOTENT | \
+						PMA_WRITE_IDEMPOTENT)
+#define PMA_NONCOHERENT_MEMORY		(PMA_NONCACHEABLE_MEMORY | PMA_CACHEABLE)
+#define PMA_NORMAL_MEMORY		(PMA_NONCOHERENT_MEMORY | PMA_COHERENT)
+
+#define PMR_ALIAS_MASK			(0xff << 24)
+#define PMR_ALIAS(n)			((n) << 24)
+
+#endif /* _DT_BINDINGS_RISCV_PHYSICAL_MEMORY_H */
-- 
2.47.2