[meta-rockchip][PATCH v2] trusted-firmware-a: use 1500000 baud for serial console

[meta-rockchip][PATCH v2] trusted-firmware-a: use 1500000 baud for serial console

[Yann Dirson]

From: Yann Dirson <yann@blade-group.com>

TF-A runs between two u-boot stages which both uses 1500000 baud, it
just makes no sense to use the same UART at a different rate.

Here is a sample session with the successive stages, with TF-A artificially
separated for emphasis:

 [20210406-175438.135934] U-Boot TPL 2021.01 (Jan 11 2021 - 18:11:43)
 [20210406-175438.135956] Channel 0: DDR3, 933MHz
 [20210406-175438.236974] BW=32 Col=10 Bk=8 CS0 Row=15 CS=1 Die BW=16 Size=1024MB
 [20210406-175438.237000] Channel 1: DDR3, 933MHz
 [20210406-175438.237004] BW=32 Col=10 Bk=8 CS0 Row=15 CS=1 Die BW=16 Size=1024MB
 [20210406-175438.237008] 256B stride
 [20210406-175438.237012] Trying to boot from BOOTROM
 [20210406-175438.237015] Returning to boot ROM...
 [20210406-175438.237018]
 [20210406-175438.573394] U-Boot SPL 2021.01 (Jan 11 2021 - 18:11:43 +0000)
 [20210406-175438.573431] Trying to boot from MMC1

 [20210406-175438.589254] NOTICE:  BL31: v2.3():v2.3-dirty
 [20210406-175440.534055] NOTICE:  BL31: Built : 15:56:43, Apr 20 2020

 [20210406-175441.393423] U-Boot 2021.01 (Jan 11 2021 - 18:11:43 +0000)
 [20210406-175441.393429]
 [20210406-175441.393433] SoC: Rockchip rk3399

Signed-off-by: Yann Dirson <yann@blade-group.com>
---
 .../files/serial-console-baudrate.patch       | 36 +++++++++++++++++++
 .../trusted-firmware-a_%.bbappend             |  5 +++
 2 files changed, 41 insertions(+)
 create mode 100644 recipes-bsp/trusted-firmware-a/files/serial-console-baudrate.patch

Changes in v2:
 - added Upstream-Status tag

diff --git a/recipes-bsp/trusted-firmware-a/files/serial-console-baudrate.patch b/recipes-bsp/trusted-firmware-a/files/serial-console-baudrate.patch
new file mode 100644
index 0000000..2d6e9bf
--- /dev/null
+++ b/recipes-bsp/trusted-firmware-a/files/serial-console-baudrate.patch
@@ -0,0 +1,36 @@
+From 840d6b6420e1fd8cdf6e4de7fa58a6f8de151622 Mon Sep 17 00:00:00 2001
+From: Yann Dirson <yann@blade-group.com>
+Date: Tue, 6 Apr 2021 17:28:45 +0200
+Subject: [PATCH] Set serial console baudrate back to 1500000.
+Upstream-Status: Inappropriate[other]
+
+TF-A runs between two u-boot stages which both uses 1500000 baud, it
+just makes no sense to use the same UART at a different rate.
+
+This effectively reverts part of 0c05748bdebfad9fa43a80962186438bb8fbce62.
+Main reason for that change stated in https://developer.trustedfirmware.org/T762
+is ChromeOS compatibility.
+
+Looks like this patch may become unnecessary in the future, when
+u-boot and TF-A get to communicate this value.
+
+---
+ plat/rockchip/rk3399/rk3399_def.h | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/plat/rockchip/rk3399/rk3399_def.h b/plat/rockchip/rk3399/rk3399_def.h
+index ba83242eb..8d6ecfbe6 100644
+--- a/plat/rockchip/rk3399/rk3399_def.h
++++ b/plat/rockchip/rk3399/rk3399_def.h
+@@ -17,7 +17,7 @@
+ /**************************************************************************
+  * UART related constants
+  **************************************************************************/
+-#define RK3399_BAUDRATE			115200
++#define RK3399_BAUDRATE			1500000
+ #define RK3399_UART_CLOCK		24000000
+ 
+ /******************************************************************************
+-- 
+2.30.2
+
diff --git a/recipes-bsp/trusted-firmware-a/trusted-firmware-a_%.bbappend b/recipes-bsp/trusted-firmware-a/trusted-firmware-a_%.bbappend
index 442dee8..1942c17 100644
--- a/recipes-bsp/trusted-firmware-a/trusted-firmware-a_%.bbappend
+++ b/recipes-bsp/trusted-firmware-a/trusted-firmware-a_%.bbappend
@@ -4,3 +4,8 @@ DEPENDS_append_rk3399 = " virtual/arm-none-eabi-gcc-native"
 
 COMPATIBLE_MACHINE_append_rk3399 = "|rk3399"
 COMPATIBLE_MACHINE_append_rk3328 = "|rk3328"
+
+FILESEXTRAPATHS_prepend := "${THISDIR}/files:"
+SRC_URI += "\
+    file://serial-console-baudrate.patch \
+"
-- 
2.30.2

Re: [meta-rockchip][PATCH v2] trusted-firmware-a: use 1500000 baud for serial console

[Trevor Woerner]

Tested with rock-pi-4b and applied to master.
Thanks!