[U-Boot] [PATCH] rpi: Support both UART interfaces.

[Andreas Färber]

Am 02.04.2017 um 10:26 schrieb Alex Deymo:
> The Raspberry Pi 3 has two UART interfaces that can be pinmuxed to the
> header pins. The PL011 is by default muxed to the Bluetooth chip and
> the mini-UART can be muxed to the pin headers passing "enabled_uart=1"

"enable_uart=1"

> in the config.txt file.
> 
> Passing "enable_uart=1" has other implications, since the baudrate of
> the miniuart depends on the clock frequency of the main core, which
> is normally dynamic unless enable_uart=1 is set. If Bluetooth is not
> used or not required, it is possible to set the PL011 UART to the
> header pins passing either "dtoverlay=pi3-disable-bt" or
> "dtoverlay=pi3-miniuart-bt" to disable Bluetooth or use it via the
> miniuart respectively.
> 
> This patch disables (for U-Boot) the UARTs modules not muxed to the

"UART modules" or "UARTs"

> header pins so the serial port is used only if available in the
> header pins, avoiding writing to the Bluetooth chip if needed. This
> allows to enable the PL01X driver for the Raspberry Pi 3, previously
> disabled for that board, which can be used for the U-Boot console if
> properly configured in the device tree.
> 
> Note that in order to get the PL01X driver in the Raspberry Pi 3 to
> work with U-Boot the device tree must set "skip-init" in the uart0
> block, for example this device tree fragment would do it:
> 
> 	fragment at 0 {
> 		target = <&uart0>;
> 		__overlay__ {
> 			skip-init;
> 		};
> 	};
> 
> Test: Booted a rpi3 with either UART output.
> Signed-off-by: Alex Deymo <deymo at google.com>
> ---
>  board/raspberrypi/rpi/rpi.c             | 78 +++++++++++++++++++++++----------
>  drivers/serial/serial_pl01x.c           |  3 ++
>  include/configs/rpi.h                   |  8 +++-
>  include/dm/platform_data/serial_pl01x.h |  2 +
>  4 files changed, 66 insertions(+), 25 deletions(-)

I've given this patch a shot on the Zero W with rpi_defconfig, but no
luck. I tried with and without enable_uart=1, and I enabled uart1 in the
-b.dts. With vanilla U-Boot I got the rainbow screen; the patched master
branch shows a black screen and some activity on the ACT LED.

Does the W require a new defconfig after all?

Regards,
Andreas

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