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@0 { > target = <&uart0>; > __overlay__ { > skip-init; > }; > }; > > Test: Booted a rpi3 with either UART output. > Signed-off-by: Alex Deymo <de...@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 -- SUSE Linux GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Felix Imendörffer, Jane Smithard, Graham Norton HRB 21284 (AG Nürnberg) _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot