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commit cd4fe549eefbd0701b30dc5ec285eee06c4e94f1 Author: Ulaş Sertan Kemeç <[email protected]> AuthorDate: Tue Aug 4 11:38:19 2026 +0300 arch/arm/am67: Add a RAT sliding window for 36-bit DDR access. J722S maps DDR above the first 2 GB at 0x8_8000_0000, out of reach of the 32-bit R5F, while a 64-bit Linux peer posts virtio buffers there. Dedicates RAT region 0 as a 16 MB window at 0xFE000000. am67_rat_map() re-aims it and returns a pointer plus the bytes left before the edge, so callers can split copies that straddle it. The window is Non-cacheable, since it retargets at runtime and cached lines would alias across physical blocks. A mapping is valid only until the next call; the sole user, vhost-net, is serialised on the netdev work thread. Assisted-by: Claude Code:claude-fable-5 Signed-off-by: Ulaş Sertan Kemeç <[email protected]> --- arch/arm/src/am67/CMakeLists.txt | 10 +++- arch/arm/src/am67/Make.defs | 1 + arch/arm/src/am67/am67_mpuinit.c | 7 +++ arch/arm/src/am67/am67_rat.c | 114 +++++++++++++++++++++++++++++++++++++++ arch/arm/src/am67/am67_rat.h | 54 +++++++++++++++++++ 5 files changed, 184 insertions(+), 2 deletions(-) diff --git a/arch/arm/src/am67/CMakeLists.txt b/arch/arm/src/am67/CMakeLists.txt index a7327584426..d0f11e6c6a0 100644 --- a/arch/arm/src/am67/CMakeLists.txt +++ b/arch/arm/src/am67/CMakeLists.txt @@ -20,8 +20,14 @@ # # ############################################################################## -set(SRCS am67_boot.c am67_irq.c am67_mpuinit.c am67_pinmux.c am67_serial.c - am67_timer.c) +set(SRCS + am67_boot.c + am67_irq.c + am67_mpuinit.c + am67_pinmux.c + am67_rat.c + am67_serial.c + am67_timer.c) if(CONFIG_RPTUN) list(APPEND SRCS am67_rptun.c) diff --git a/arch/arm/src/am67/Make.defs b/arch/arm/src/am67/Make.defs index ed55717cf0e..3503067fd6e 100644 --- a/arch/arm/src/am67/Make.defs +++ b/arch/arm/src/am67/Make.defs @@ -48,3 +48,4 @@ endif ifeq ($(CONFIG_RPTUN),y) CHIP_CSRCS += am67_rptun.c endif +CHIP_CSRCS += am67_rat.c diff --git a/arch/arm/src/am67/am67_mpuinit.c b/arch/arm/src/am67/am67_mpuinit.c index c8073fff520..dd7b448290f 100644 --- a/arch/arm/src/am67/am67_mpuinit.c +++ b/arch/arm/src/am67/am67_mpuinit.c @@ -31,6 +31,7 @@ #include <sys/param.h> #include "am67_mpuinit.h" +#include "am67_rat.h" #include "mpu.h" /**************************************************************************** @@ -85,5 +86,11 @@ void am67_mpu_init(void) am67_ipc_shm_region(AM67_IPC_SHM0_START_ADDR, AM67_IPC_SHM0_SIZE); am67_ipc_shm_region(AM67_IPC_SHM1_START_ADDR, AM67_IPC_SHM1_SIZE); + /* RAT sliding window (am67_rat.c): retargeted at runtime onto arbitrary + * 36-bit physical blocks, so it must never be cached. + */ + + am67_ipc_shm_region(AM67_RAT_WIN_BASE, AM67_RAT_WIN_SIZE); + mpu_control(true); } diff --git a/arch/arm/src/am67/am67_rat.c b/arch/arm/src/am67/am67_rat.c new file mode 100644 index 00000000000..867abc7ba62 --- /dev/null +++ b/arch/arm/src/am67/am67_rat.c @@ -0,0 +1,114 @@ +/**************************************************************************** + * arch/arm/src/am67/am67_rat.c + * + * SPDX-License-Identifier: Apache-2.0 + * + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. The + * ASF licenses this file to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance with the + * License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT + * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the + * License for the specific language governing permissions and limitations + * under the License. + * + ****************************************************************************/ + +/**************************************************************************** + * Included Files + ****************************************************************************/ + +/* Region Address Translator (RAT) sliding window. + * + * The Cortex-R5F is a 32-bit master on a 36-bit SoC: DDR beyond the first + * 2 GB lives at 0x8_8000_0000 and cannot be addressed by the core + * directly. The R5FSS integrates a per-core RAT (config space at + * 0x2ffe_0000, 4 regions) that remaps a 32-bit input window onto any + * 36-bit output address (TRM 7.2.2.6 / 7.3.2.6.4). + * + * This driver dedicates one region as a 16 MB sliding window: callers ask + * for a pointer to an arbitrary 36-bit physical address and the window is + * re-aimed at the containing 16 MB block. The window range is mapped + * Non-cacheable in the MPU (am67_mpuinit.c), so accesses through it are + * also coherent with the A53 without cache maintenance. + * + * The single window is a shared resource: the returned pointer is only + * valid until the next am67_rat_map() call, and callers must be + * serialized (the sole current user is the vhost-net driver, whose + * transmit/receive both run on the netdev work thread). + */ + +#include <nuttx/config.h> + +#include <stdint.h> +#include <stddef.h> + +#include <arch/barriers.h> + +#include "arm_internal.h" +#include "am67_rat.h" + +/**************************************************************************** + * Pre-processor Definitions + ****************************************************************************/ + +#define AM67_RAT_BASE (0x2ffe0000ul) +#define AM67_RAT_CTRL(n) (AM67_RAT_BASE + 0x20 + 0x10 * (n)) +#define AM67_RAT_ADDR(n) (AM67_RAT_BASE + 0x24 + 0x10 * (n)) +#define AM67_RAT_TRANS_L(n) (AM67_RAT_BASE + 0x28 + 0x10 * (n)) +#define AM67_RAT_TRANS_U(n) (AM67_RAT_BASE + 0x2c + 0x10 * (n)) + +#define AM67_RAT_CTRL_EN (1ul << 31) + +#define AM67_RAT_REGION (0) /* RAT region index used for the window */ +#define AM67_RAT_WIN_LOG2 (24) /* 16 MB window */ + +/**************************************************************************** + * Public Functions + ****************************************************************************/ + +/**************************************************************************** + * Name: am67_rat_map + * + * Description: + * Return a CPU pointer to the given 36-bit physical address by sliding + * the RAT window over its 16 MB block. If avail is non-NULL it + * receives the number of contiguous bytes reachable from the returned + * pointer before the window ends (callers accessing more must map + * again at the advanced address). + * + * The pointer is valid only until the next call. Not reentrant. + * + ****************************************************************************/ + +FAR void *am67_rat_map(uint64_t pa, FAR size_t *avail) +{ + static uint64_t cur_block = UINT64_MAX; + uint64_t block = pa & ~((uint64_t)AM67_RAT_WIN_SIZE - 1); + uint32_t offset = (uint32_t)(pa & (AM67_RAT_WIN_SIZE - 1)); + + if (block != cur_block) + { + putreg32(0, AM67_RAT_CTRL(AM67_RAT_REGION)); + putreg32(AM67_RAT_WIN_BASE, AM67_RAT_ADDR(AM67_RAT_REGION)); + putreg32((uint32_t)block, AM67_RAT_TRANS_L(AM67_RAT_REGION)); + putreg32((uint32_t)(block >> 32), AM67_RAT_TRANS_U(AM67_RAT_REGION)); + putreg32(AM67_RAT_CTRL_EN | AM67_RAT_WIN_LOG2, + AM67_RAT_CTRL(AM67_RAT_REGION)); + UP_DSB(); + cur_block = block; + } + + if (avail != NULL) + { + *avail = AM67_RAT_WIN_SIZE - offset; + } + + return (FAR void *)(AM67_RAT_WIN_BASE + offset); +} diff --git a/arch/arm/src/am67/am67_rat.h b/arch/arm/src/am67/am67_rat.h new file mode 100644 index 00000000000..8d8b52f5b0d --- /dev/null +++ b/arch/arm/src/am67/am67_rat.h @@ -0,0 +1,54 @@ +/**************************************************************************** + * arch/arm/src/am67/am67_rat.h + * + * SPDX-License-Identifier: Apache-2.0 + * + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. The + * ASF licenses this file to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance with the + * License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT + * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the + * License for the specific language governing permissions and limitations + * under the License. + * + ****************************************************************************/ + +#ifndef __ARCH_ARM_SRC_AM67_AM67_RAT_H +#define __ARCH_ARM_SRC_AM67_AM67_RAT_H + +/**************************************************************************** + * Included Files + ****************************************************************************/ + +#include <nuttx/config.h> + +#include <stdint.h> +#include <stddef.h> + +/**************************************************************************** + * Pre-processor Definitions + ****************************************************************************/ + +/* 32-bit address range claimed by the RAT sliding window. Must be mapped + * Non-cacheable in the MPU (am67_mpuinit.c) and must not overlap anything + * the firmware needs to address directly (NuttX RAM/IPC live in + * 0xa2000000-0xa3000000). + */ + +#define AM67_RAT_WIN_BASE (0xfe000000ul) +#define AM67_RAT_WIN_SIZE (0x01000000ul) /* 16 MB */ + +/**************************************************************************** + * Public Function Prototypes + ****************************************************************************/ + +FAR void *am67_rat_map(uint64_t pa, FAR size_t *avail); + +#endif /* __ARCH_ARM_SRC_AM67_AM67_RAT_H */
