soc: ambiq: add common cache handling for apollo5x soc

The buf_in_nocache function is to be used by various device drivers
to check if buffer is in noncacheable region.
The cacheable DMA buffer shall be put into section .ambiq_dma_buff
due to certain restrictions of the SoC.

Signed-off-by: Swift Tian <swift.tian@ambiq.com>

soc/ambiq/apollo5x/CMakeLists.txt

@@ -8,4 +8,6 @@ zephyr_include_directories(.)
 zephyr_sources_ifdef(CONFIG_PM power.c)
 zephyr_include_directories(${ZEPHYR_BASE}/soc/arm/common/cortex_m)
 
+zephyr_linker_sources(SECTIONS shared_ram.ld)
+
 set(SOC_LINKER_SCRIPT ${ZEPHYR_BASE}/include/zephyr/arch/arm/cortex_m/scripts/linker.ld CACHE INTERNAL "")

soc/ambiq/apollo5x/Kconfig

@@ -19,3 +19,20 @@ config SOC_SERIES_APOLLO5X
 	select HAS_PM
 	select SOC_EARLY_INIT_HOOK
 	select REQUIRES_FULL_LIBC
+
+config SOC_AMBIQ_DCACHE_SIZE
+	int
+	default 65536 if SOC_APOLLO510
+
+config SOC_AMBIQ_DMA_BUFF_LOCATION
+	hex "Byte offset to SRAM_BASE_ADDRESS"
+	default 0x50000
+	help
+	  This option specifies the cacheable DMA buffers' start address
+
+config SOC_AMBIQ_DMA_BUFF_ALIGNMENT
+	int "Byte alignment of the DMA buffer"
+	default DCACHE_LINE_SIZE if DCACHE
+	default 1
+	help
+	  This option specifies the DMA buffers' alignment

soc/ambiq/apollo5x/Kconfig.defconfig

@@ -9,9 +9,14 @@ rsource "Kconfig.defconfig.apollo5*"
 config CACHE_MANAGEMENT
 	default y
 
-config AMBIQ_CACHEABLE_DMA_BUFFER_ALIGNMENT
-	int
-	default DCACHE_LINE_SIZE
+config DCACHE_LINE_SIZE
+	default 32
+
+config DCACHE
+	default y
+
+config ICACHE
+	default y
 
 # Need to enlarge the IDLE stack size because the power
 # management operations are executed in the idle task

soc/ambiq/apollo5x/shared_ram.ld

@@ -0,0 +1,13 @@
+/*
+ * Copyright (c) 2025 Ambiq Micro Inc. <www.ambiq.com>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+SECTION_PROLOGUE (ambiq_dma_buff, CONFIG_SRAM_BASE_ADDRESS + CONFIG_SOC_AMBIQ_DMA_BUFF_LOCATION (NOLOAD),)
+{
+    __ambiq_dma_buff_start = .;
+    KEEP(*(SORT_BY_NAME(".ambiq_dma_buff*")))
+    . = ALIGN(CONFIG_SOC_AMBIQ_DMA_BUFF_ALIGNMENT);
+    __ambiq_dma_buff_end = .;
+} GROUP_LINK_IN(RAMABLE_REGION)

soc/ambiq/apollo5x/soc.c

@@ -7,7 +7,16 @@
 #include <zephyr/init.h>
 #include <zephyr/cache.h>
 #include <zephyr/logging/log.h>
-#include "soc.h"
+#include <zephyr/mem_mgmt/mem_attr.h>
+#ifdef CONFIG_DCACHE
+#include <zephyr/dt-bindings/memory-attr/memory-attr-arm.h>
+#endif /* CONFIG_DCACHE */
+
+#ifdef CONFIG_NOCACHE_MEMORY
+#include <zephyr/linker/linker-defs.h>
+#endif /* CONFIG_NOCACHE_MEMORY */
+
+#include <soc.h>
 
 LOG_MODULE_REGISTER(soc, CONFIG_SOC_LOG_LEVEL);
 
@@ -48,3 +57,25 @@ void soc_early_init_hook(void)
 	/* Enable Dcache */
 	sys_cache_data_enable();
 }
+
+#if CONFIG_CACHE_MANAGEMENT
+bool buf_in_nocache(uintptr_t buf, size_t len_bytes)
+{
+	bool buf_within_nocache = false;
+
+#if CONFIG_NOCACHE_MEMORY
+	/* Check if buffer is in nocache region defined by the linker */
+	buf_within_nocache = (buf >= ((uintptr_t)_nocache_ram_start)) &&
+			     ((buf + len_bytes - 1) <= ((uintptr_t)_nocache_ram_end));
+	if (buf_within_nocache) {
+		return true;
+	}
+#endif /* CONFIG_NOCACHE_MEMORY */
+
+	/* Check if buffer is in nocache memory region defined in DT */
+	buf_within_nocache = mem_attr_check_buf((void *)buf, len_bytes,
+						DT_MEM_ARM(ATTR_MPU_RAM_NOCACHE)) == 0;
+
+	return buf_within_nocache;
+}
+#endif

soc/ambiq/apollo5x/soc.h

@@ -9,4 +9,6 @@
 
 #include <am_mcu_apollo.h>
 
+bool buf_in_nocache(uintptr_t buf, size_t len_bytes);
+
 #endif /* __SOC_H__ */