From 6d5c61de74c6c2356707f041537e3c66def2b1bc Mon Sep 17 00:00:00 2001
From: Pete Batard <pete@akeo.ie>
Date: Tue, 13 Nov 2018 13:14:26 +0000
Subject: [PATCH] rpi3: add RPI3_RUNTIME_UART build option

Some OSes (e.g. Ubuntu 18.04 LTS on Raspberry Pi 3) may disable the
runtime UART in a manner that prevents the system from rebooting if
ATF tries to send runtime messages there.

Also, we don't want the firmware to share the UART with normal
world, as this can be a DoS attack vector into the secure world.

This patch fixes these 2 issues by introducing new build option
RPI3_RUNTIME_UART, that disables the runtime UART by default.

Fixes ARM-software/tf-issues#647

Signed-off-by: Pete Batard <pete@akeo.ie>
---
 docs/plat/rpi3.rst      | 4 ++++
 plat/rpi3/platform.mk   | 5 +++++
 plat/rpi3/rpi3_common.c | 7 +++++--
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/docs/plat/rpi3.rst b/docs/plat/rpi3.rst
index db475646b..ea8171fa0 100644
--- a/docs/plat/rpi3.rst
+++ b/docs/plat/rpi3.rst
@@ -231,6 +231,10 @@ The following build options are supported:
   ``RPI3_DIRECT_LINUX_BOOT=1``. This option allows to specify the location of a
   DTB in memory.
 
+- ``RPI3_RUNTIME_UART``: Indicates whether the UART should be used at runtime
+  or disabled. ``-1`` (default) disables the runtime UART. Any other value
+  enables the default UART (currently UART1) for runtime messages.
+
 - ``BL32``: This port can load and run OP-TEE. The OP-TEE image is optional.
   Please use the code from `here <https://github.com/OP-TEE/optee_os>`__.
   Build the Trusted Firmware with option ``BL32=tee-header_v2.bin
diff --git a/plat/rpi3/platform.mk b/plat/rpi3/platform.mk
index 36c1ee2b4..07d2bf1e0 100644
--- a/plat/rpi3/platform.mk
+++ b/plat/rpi3/platform.mk
@@ -109,6 +109,10 @@ RPI3_BL33_IN_AARCH32		:= 0
 # Assume that BL33 isn't the Linux kernel by default
 RPI3_DIRECT_LINUX_BOOT		:= 0
 
+# UART to use at runtime. -1 means the runtime UART is disabled.
+# Any other value means the default UART will be used.
+RPI3_RUNTIME_UART               := -1
+
 # BL32 location
 RPI3_BL32_RAM_LOCATION	:= tdram
 ifeq (${RPI3_BL32_RAM_LOCATION}, tsram)
@@ -126,6 +130,7 @@ $(eval $(call add_define,RPI3_BL32_RAM_LOCATION_ID))
 $(eval $(call add_define,RPI3_BL33_IN_AARCH32))
 $(eval $(call add_define,RPI3_DIRECT_LINUX_BOOT))
 $(eval $(call add_define,RPI3_PRELOADED_DTB_BASE))
+$(eval $(call add_define,RPI3_RUNTIME_UART))
 
 # Verify build config
 # -------------------
diff --git a/plat/rpi3/rpi3_common.c b/plat/rpi3/rpi3_common.c
index 18ff1c82e..c7e8b3a75 100644
--- a/plat/rpi3/rpi3_common.c
+++ b/plat/rpi3/rpi3_common.c
@@ -96,6 +96,10 @@ static console_16550_t rpi3_console;
 
 void rpi3_console_init(void)
 {
+	int console_scope = CONSOLE_FLAG_BOOT;
+#if RPI3_RUNTIME_UART != -1
+	console_scope |= CONSOLE_FLAG_RUNTIME;
+#endif
 	int rc = console_16550_register(PLAT_RPI3_UART_BASE,
 					PLAT_RPI3_UART_CLK_IN_HZ,
 					PLAT_RPI3_UART_BAUDRATE,
@@ -109,8 +113,7 @@ void rpi3_console_init(void)
 		panic();
 	}
 
-	console_set_scope(&rpi3_console.console,
-			  CONSOLE_FLAG_BOOT | CONSOLE_FLAG_RUNTIME);
+	console_set_scope(&rpi3_console.console, console_scope);
 }
 
 /*******************************************************************************