Pete Batard bfe3483019 Platform/RPi: Add serial lib for runtime PL011 vs miniUART detection ...

The Raspberry Pi platform contains two UARTs, one PL011-based and the
other (called miniUART) 16650-compatible, that are pinmuxed to the GPIO
serial port according to whether a Device Tree overlay is present in
config.txt or not. In most cases, it takes only the user commenting or
uncommenting an overlay line in config.txt to switch between PL011 and
miniUART.

As such, the use of a build time option to select the UART should be
avoided when it is effectively possible to detect which of the UART is
in use at runtime, through a simple MMIO call.

This patch does just this by adding a new DualSerialPortLib that
directs the SerialPortLib implementation to use either 16650 or PL011
according to the GPIO pinmuxing.

It should be noted that this code mostly a merge of
* MdeModulePkg/Library/BaseSerialPortLib16550
* ArmPlatformPkg/Library/PL011SerialPortLib
with non-relevant elements stripped from BaseSerialPortLib16550 (such
as PCI support) and a new call added to retreive the 16650 baudrate
divisor, since it is dependent on the platform's VPU's clock divisor.

Signed-off-by: Pete Batard <pete@akeo.ie>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

2020-02-14 10:05:09 +01:00

..

DualSerialPortLib.c

Platform/RPi: Add serial lib for runtime PL011 vs miniUART detection

2020-02-14 10:05:09 +01:00

DualSerialPortLib.inf

Platform/RPi: Add serial lib for runtime PL011 vs miniUART detection

2020-02-14 10:05:09 +01:00