serial: ns16550: Support debug UART

[oweals/u-boot.git] / drivers / serial / Kconfig

diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index a0b6e02b5462e5fc515a28d7f40b04a46c22018d..1686a1f951e860757bbc656678fbfdf6088b39b9 100644 (file)
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -2,8 +2,69 @@ config DM_SERIAL
        bool "Enable Driver Model for serial drivers"
        depends on DM
        help
-         If you want to use driver model for serial drivers, say Y.
-         To use legacy serial drivers, say N.
+         Enable driver model for serial. This replaces
+         drivers/serial/serial.c with the serial uclass, which
+         implements serial_putc() etc. The uclass interface is
+         defined in include/serial.h.
+
+config DEBUG_UART
+       bool "Enable an early debug UART for debugging"
+       help
+         The debug UART is intended for use very early in U-Boot to debug
+         problems when an ICE or other debug mechanism is not available.
+
+         To use it you should:
+         - Make sure your UART supports this interface
+         - Enable CONFIG_DEBUG_UART
+         - Enable the CONFIG for your UART to tell it to provide this interface
+               (e.g. CONFIG_DEBUG_UART_NS16550)
+         - Define the required settings as needed (see below)
+         - Call debug_uart_init() before use
+         - Call debug_uart_putc() to output a character
+
+         Depending on your platform it may be possible to use this UART before
+         a stack is available.
+
+         If your UART does not support this interface you can probably add
+         support quite easily. Remember that you cannot use driver model and
+         it is preferred to use no stack.
+
+         You must not use this UART once driver model is working and the
+         serial drivers are up and running (done in serial_init()). Otherwise
+         the drivers may conflict and you will get strange output.
+
+choice
+       prompt "Select which UART will provide the debug UART"
+       depends on DEBUG_UART
+
+config DEBUG_UART_NS16550
+       bool "ns16550"
+       help
+         Select this to enable a debug UART using the ns16550 driver. You
+         will need to provide parameters to make this work. The driver will
+         be available until the real driver model serial is running.
+
+endchoice
+
+config DEBUG_UART_BASE
+       hex "Base address of UART"
+       depends on DEBUG_UART
+       help
+         This is the base address of your UART for memory-mapped UARTs.
+
+         A default should be provided by your board, but if not you will need
+         to use the correct value here.
+
+config DEBUG_UART_CLOCK
+       int "UART input clock"
+       depends on DEBUG_UART
+       help
+         The UART input clock determines the speed of the internal UART
+         circuitry. The baud rate is derived from this by dividing the input
+         clock down.
+
+         A default should be provided by your board, but if not you will need
+         to use the correct value here.
 
 config UNIPHIER_SERIAL
        bool "UniPhier on-chip UART support"