From: Yann Dirson <yann@...>

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 artificial=
ly
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=3D32 Col=3D10 Bk=3D8 CS0 Row=3D15 CS=3D1 Die=
BW=3D16 Size=3D1024MB
[20210406-175438.237000] Channel 1: DDR3, 933MHz
[20210406-175438.237004] BW=3D32 Col=3D10 Bk=3D8 CS0 Row=3D15 CS=3D1 Die=
BW=3D16 Size=3D1024MB
[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 +000=
0)
[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@...>
---
.../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-b=
audrate.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.pat=
ch
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@...>
+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 0c05748bdebfad9fa43a80962186438bb8fbce6=
2.
+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/rk=
3399_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
+=20
+ /**********************************************************************=
********
+--=20
+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 =3D " virtual/arm-none-eabi-gcc-nat=
ive"
=20
COMPATIBLE_MACHINE_append_rk3399 =3D "|rk3399"
COMPATIBLE_MACHINE_append_rk3328 =3D "|rk3328"
+
+FILESEXTRAPATHS_prepend :=3D "${THISDIR}/files:"
+SRC_URI +=3D "\
+ file://serial-console-baudrate.patch \
+"
--=20
2.30.2

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