Ast10x0 : FMC flash backend for the flash service

services/flash/BUILD.bazel

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+# Licensed under the Apache-2.0 license
+# SPDX-License-Identifier: Apache-2.0
+
+load("@rules_rust//rust:defs.bzl", "rust_library")
+
+package(default_visibility = ["//visibility:public"])
+
+rust_library(
+    name = "opcode",
+    srcs = [
+        "opcode.rs",
+    ],
+    crate_name = "services_flash_opcode",
+    edition = "2024",
+    deps = [
+        "//hal/blocking/flash",
+        "//util/types",
+        "@rust_crates//:zerocopy",
+    ],
+)
+
+rust_library(
+    name = "client",
+    srcs = [
+        "client.rs",
+    ],
+    crate_name = "services_flash_client",
+    edition = "2024",
+    deps = [
+        ":opcode",
+        "//hal/blocking/flash",
+        "//util/error",
+        "//util/ipc",
+        "//util/types",
+        "@pigweed//pw_kernel/userspace",
+        "@pigweed//pw_log/rust:pw_log",
+        "@rust_crates//:zerocopy",
+    ],
+)
+
+rust_library(
+    name = "server",
+    srcs = [
+        "server.rs",
+    ],
+    crate_name = "services_flash_server",
+    edition = "2024",
+    deps = [
+        ":opcode",
+        "//hal/blocking/flash",
+        "//util/error",
+        "//util/ipc",
+        "//util/types",
+        "@pigweed//pw_kernel/userspace",
+        "@pigweed//pw_log/rust:pw_log",
+        "@rust_crates//:zerocopy",
+    ],
+)

services/flash/README.md

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+# Flash Service
+
+The Flash Service provides a centralized interface for userspace applications to interact with on-chip and external flash memory. This is achieved via an IPC-based client-server architecture.
+
+## Overview
+
+Applications interact with flash through the `Flash` trait, typically using the `FlashIpcClient` implementation. All operations are blocking from the perspective of the caller.
+
+### Key Features
+- **Partition Support**: Access to both primary Data partitions and auxiliary Info partitions.
+- **Flexible Erase**: Support for multiple erase granularities (e.g., page vs. block) as reported by the hardware.
+- **Unified Addressing**: A logical `FlashAddress` system that abstracts hardware-specific bank and page layouts.
+
+## Usage
+
+To use the flash service, initialize a `FlashIpcClient` with a handle to the flash service:
+
+```rust
+use hal_flash::{Flash, FlashAddress};
+use services_flash_client::FlashIpcClient;
+use util_ipc::IpcHandle;
+
+// 1. Connect to the flash service
+let mut flash = FlashIpcClient::new(IpcHandle::new(FLASH_SERVICE_HANDLE))?;
+
+// 2. Retrieve device geometry
+let (total_size, page_size, erasable_bitmap) = flash.geometry();
+
+// 3. Erase a block (using the default page size)
+let addr = FlashAddress::new(0x1000);
+flash.erase(addr, page_size)?;
+
+// 4. Program data
+flash.program(addr, b"Hello, Flash!")?;
+
+// 5. Read data back
+let mut buf = [0u8; 13];
+flash.read(addr, &mut buf)?;
+```
+
+## The `Flash` Trait
+
+The primary interface for flash operations:
+
+- `geometry() -> (NonZero<usize>, PowerOf2Usize, u32)`: Returns the total capacity, the default/smallest page size, and a bitmap of all supported erase block sizes.
+- `read(addr, buf)`: Reads data from the specified address.
+- `erase(addr, size)`: Erases a block of the specified size. The size must be one of the values supported in the `erasable_bitmap`.
+- `program(addr, data)`: Writes data to the specified address. Flash must be erased before programming.
+
+### Understanding `erasable_bitmap`
+The `erasable_bitmap` is a `u32` where each set bit `i` indicates that an erase block size of `2^i` bytes is supported.
+- Bit 11 set (`0x800`) -> 2048-byte erase supported.
+- Bit 16 set (`0x10000`) -> 64KB erase supported.
+
+## Addressing
+
+Flash memory is addressed using the `FlashAddress` type, which wraps a single 32-bit `offset`.
+
+On platforms like Earlgrey, the most significant bit (MSB) of this offset is used to distinguish between different partitions:
+- **DATA partition**: MSB is 0 (offset < 0x80000000).
+- **INFO partition**: MSB is 1 (offset >= 0x80000000).
+
+The `EarlgreyFlashAddress` trait (from `earlgrey_util`) provides helper methods to construct and inspect addresses:
+- `FlashAddress::data(offset)`: Accesses the main data partition.
+- `FlashAddress::info(bank, page, offset)`: Accesses specific info pages.
+
+## Implementation Details
+
+The service is built on several layers of abstraction:
+
+### IPC Layer
+- **`FlashIpcServer`**: Wraps a hardware-backed `Flash` implementation and dispatches IPC requests.
+- **`FlashIpcClient`**: Implements the `Flash` trait by proxying calls to the server.
+
+### Hardware Abstraction
+- **`FlashDriver` Trait**: Defines the low-level, often asynchronous, interface for hardware drivers.
+- **`BlockingFlash`**: A wrapper that converts a `FlashDriver` into a synchronous `Flash` implementation using a provided blocking mechanism.
+
+### Component Diagram
+
+```mermaid
+graph TD
+    Client[Userspace Application] -- "Flash Trait" --> IPC_Client[FlashIpcClient]
+    IPC_Client -- "IPC" --> IPC_Server[FlashIpcServer]
+    IPC_Server -- "Flash Trait" --> BlockingFlash[BlockingFlash]
+    BlockingFlash -- "FlashDriver Trait" --> HardwareDriver[e.g., EmbeddedFlash]
+    HardwareDriver --> HW[Flash Controller]
+```

services/flash/client.rs

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+// Licensed under the Apache-2.0 license
+// SPDX-License-Identifier: Apache-2.0
+
+//! Flash IPC client implementation.
+
+#![no_std]
+use core::num::NonZero;
+
+use hal_flash::{Flash, FlashAddress};
+use services_flash_opcode::*;
+use userspace::time::Instant;
+use util_error::{self as error, ErrorCode};
+use util_ipc::{IpcChannel, IpcHandle};
+use util_types::PowerOf2Usize;
+use zerocopy::{FromZeros, IntoBytes};
+
+/// An IPC-based client for the flash service.
+///
+/// This struct implements the `Flash` trait by proxying requests to a remote
+/// flash server via an IPC handle.
+pub struct FlashIpcClient {
+    ipc: IpcHandle,
+    page_size: PowerOf2Usize,
+    total_size: NonZero<usize>,
+    erasable_sizes_bitmap: u32,
+}
+
+impl FlashIpcClient {
+    /// Creates a new `FlashIpcClient` using the provided IPC handle.
+    ///
+    /// This constructor will perform an IPC transaction to retrieve flash
+    /// geometry and capabilities from the server.
+    pub fn new(ipc: IpcHandle) -> Result<Self, ErrorCode> {
+        let mut info = FlashInfo::new_zeroed();
+        let mut result = 0u32;
+
+        ipc.transact(
+            &[IPC_OP_FLASH_GET_INFO.as_bytes()],
+            &mut [result.as_mut_bytes(), info.as_mut_bytes()],
+            Instant::MAX,
+        )
+        .map_err(ErrorCode::kernel_error)?;
+        ErrorCode::check_status(result)?;
+
+        let Some(page_size) = PowerOf2Usize::new(info.page_size as usize) else {
+            return Err(error::FLASH_GENERIC_INVALID_PAGE_SIZE);
+        };
+        let Some(total_size) = NonZero::new(info.total_size as usize) else {
+            return Err(error::FLASH_GENERIC_INVALID_SIZE);
+        };
+        Ok(Self {
+            ipc,
+            page_size,
+            total_size,
+            erasable_sizes_bitmap: info.erasable_sizes_bitmap,
+        })
+    }
+}
+
+impl Flash for FlashIpcClient {
+    type Error = ErrorCode;
+    fn geometry(&mut self) -> Result<(NonZero<usize>, PowerOf2Usize, u32), ErrorCode> {
+        Ok((self.total_size, self.page_size, self.erasable_sizes_bitmap))
+    }
+
+    fn erase(&mut self, start_addr: FlashAddress, size: PowerOf2Usize) -> Result<(), ErrorCode> {
+        let mut result = 0u32;
+        let op = EraseOp {
+            address: start_addr,
+            size: size.get() as u32,
+        };
+        self.ipc
+            .transact(
+                &[IPC_OP_FLASH_ERASE.as_bytes(), op.as_bytes()],
+                &mut [result.as_mut_bytes()],
+                Instant::MAX,
+            )
+            .map_err(ErrorCode::kernel_error)?;
+        ErrorCode::check_status(result)
+    }
+
+    fn program(&mut self, start_addr: FlashAddress, data: &[u8]) -> Result<(), ErrorCode> {
+        let mut result = 0u32;
+        self.ipc
+            .transact(
+                &[IPC_OP_FLASH_PROGRAM.as_bytes(), start_addr.as_bytes(), data],
+                &mut [result.as_mut_bytes()],
+                Instant::MAX,
+            )
+            .map_err(ErrorCode::kernel_error)?;
+        ErrorCode::check_status(result)
+    }
+
+    fn read(&mut self, start_addr: FlashAddress, buf: &mut [u8]) -> Result<(), ErrorCode> {
+        let mut result = 0u32;
+        let op = ReadOp {
+            address: start_addr,
+            length: buf.len() as u32,
+        };
+        self.ipc
+            .transact(
+                &[IPC_OP_FLASH_READ.as_bytes(), op.as_bytes()],
+                &mut [result.as_mut_bytes(), buf],
+                Instant::MAX,
+            )
+            .map_err(ErrorCode::kernel_error)?;
+        ErrorCode::check_status(result)
+    }
+}

services/flash/opcode.rs

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+// Licensed under the Apache-2.0 license
+// SPDX-License-Identifier: Apache-2.0
+
+//! Shared flash IPC opcodes and data structures.
+
+#![no_std]
+
+use hal_flash::FlashAddress;
+use util_types::Opcode;
+use zerocopy::{FromBytes, Immutable, IntoBytes, KnownLayout};
+
+/// IPC opcode for erasing a flash block.
+pub const IPC_OP_FLASH_ERASE: Opcode = Opcode::new(*b"FLET");
+/// IPC opcode for programming flash.
+pub const IPC_OP_FLASH_PROGRAM: Opcode = Opcode::new(*b"FLWR");
+/// IPC opcode for reading from flash.
+pub const IPC_OP_FLASH_READ: Opcode = Opcode::new(*b"FLRD");
+/// IPC opcode for retrieving flash information.
+pub const IPC_OP_FLASH_GET_INFO: Opcode = Opcode::new(*b"FLIN");
+
+/// Information about the flash device.
+#[derive(FromBytes, Immutable, IntoBytes, KnownLayout)]
+#[repr(C)]
+pub struct FlashInfo {
+    /// The size of a single flash page in bytes.
+    pub page_size: u32,
+    /// The total size of the flash in bytes.
+    pub total_size: u32,
+    /// A bitmap of supported erase block sizes.
+    pub erasable_sizes_bitmap: u32,
+}
+
+/// Arguments for the `IPC_OP_FLASH_ERASE` request.
+#[derive(FromBytes, IntoBytes, KnownLayout, Immutable)]
+#[repr(C)]
+pub struct EraseOp {
+    /// The start address of the block to erase.
+    pub address: FlashAddress,
+    /// The size of the block to erase in bytes.
+    pub size: u32,
+}
+
+/// Arguments for the `IPC_OP_FLASH_READ` request.
+#[derive(FromBytes, IntoBytes, KnownLayout, Immutable)]
+#[repr(C)]
+pub struct ReadOp {
+    /// The start address to read from.
+    pub address: FlashAddress,
+    /// The number of bytes to read.
+    pub length: u32,
+}