From e9163992cfdc24d1ac07d5535230e7480e6bf89d Mon Sep 17 00:00:00 2001
From: Dawid Niedzwiecki <dawidn@google.com>
Date: Fri, 22 Nov 2024 16:50:02 +0100
Subject: [PATCH] mgmt: ec_host_cmd: add support for nocache buffers

Some backends use DMA. Usually, DMA doesn't work correctly, when memory
to transfer is cached. Add a config to place the common buffers in the
nocache section.

Signed-off-by: Dawid Niedzwiecki <dawidn@google.com>
---
 subsys/mgmt/ec_host_cmd/Kconfig               |  9 +++++++++
 subsys/mgmt/ec_host_cmd/ec_host_cmd_handler.c | 15 +++++++++++----
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/subsys/mgmt/ec_host_cmd/Kconfig b/subsys/mgmt/ec_host_cmd/Kconfig
index 3e46dc9ce4f..1cd5c8acba3 100644
--- a/subsys/mgmt/ec_host_cmd/Kconfig
+++ b/subsys/mgmt/ec_host_cmd/Kconfig
@@ -76,6 +76,15 @@ config EC_HOST_CMD_HANDLER_RX_BUFFER_DEF
 	help
 	  The handler defines common rx buffer
 
+config EC_HOST_CMD_NOCACHE_BUFFERS
+	bool "Place RX and TX buffers in __nocache section"
+	default y if DCACHE && DMA
+	depends on EC_HOST_CMD_HANDLER_TX_BUFFER_DEF || EC_HOST_CMD_HANDLER_RX_BUFFER_DEF
+	help
+	  DMA is often use for communication, however it usually requires
+	  uncached memory. Add possibility to place the RX and TX buffers in the
+	  __nocache section.
+
 config EC_HOST_CMD_INITIALIZE_AT_BOOT
 	bool "Initialize the host command subsystem automacitlly"
 	default y
diff --git a/subsys/mgmt/ec_host_cmd/ec_host_cmd_handler.c b/subsys/mgmt/ec_host_cmd/ec_host_cmd_handler.c
index 265c5bc854c..0e8df2316b8 100644
--- a/subsys/mgmt/ec_host_cmd/ec_host_cmd_handler.c
+++ b/subsys/mgmt/ec_host_cmd/ec_host_cmd_handler.c
@@ -6,6 +6,7 @@
 
 #include <zephyr/devicetree.h>
 #include <zephyr/kernel.h>
+#include <zephyr/linker/section_tags.h>
 #include <zephyr/logging/log.h>
 #include <zephyr/mgmt/ec_host_cmd/ec_host_cmd.h>
 #include <zephyr/mgmt/ec_host_cmd/backend.h>
@@ -32,12 +33,18 @@ BUILD_ASSERT(NUMBER_OF_CHOSEN_BACKENDS < 2, "Number of chosen backends > 1");
 #define RX_HEADER_SIZE (sizeof(struct ec_host_cmd_request_header))
 #define TX_HEADER_SIZE (sizeof(struct ec_host_cmd_response_header))
 
+#ifdef CONFIG_EC_HOST_CMD_NOCACHE_BUFFERS
+#define BUFFERS_CACHE_ATTR __nocache
+#else
+#define BUFFERS_CACHE_ATTR
+#endif
+
 COND_CODE_1(CONFIG_EC_HOST_CMD_HANDLER_RX_BUFFER_DEF,
-	    (static uint8_t hc_rx_buffer[CONFIG_EC_HOST_CMD_HANDLER_RX_BUFFER_SIZE] __aligned(4);),
-	    ())
+	    (static uint8_t hc_rx_buffer[CONFIG_EC_HOST_CMD_HANDLER_RX_BUFFER_SIZE] __aligned(4)
+	    BUFFERS_CACHE_ATTR;), ())
 COND_CODE_1(CONFIG_EC_HOST_CMD_HANDLER_TX_BUFFER_DEF,
-	    (static uint8_t hc_tx_buffer[CONFIG_EC_HOST_CMD_HANDLER_TX_BUFFER_SIZE] __aligned(4);),
-	    ())
+	    (static uint8_t hc_tx_buffer[CONFIG_EC_HOST_CMD_HANDLER_TX_BUFFER_SIZE] __aligned(4)
+	    BUFFERS_CACHE_ATTR;), ())
 
 #ifdef CONFIG_EC_HOST_CMD_DEDICATED_THREAD
 static K_KERNEL_STACK_DEFINE(hc_stack, CONFIG_EC_HOST_CMD_HANDLER_STACK_SIZE);