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![Simon Glass](/assets/img/avatar_default.png)
Add debug UART functions to permit ns16550 to provide an early debug UART. Try to avoid using the stack so that this can be called from assembler before a stack is set up (at least on ARM and PowerPC). Signed-off-by: Simon Glass <sjg@chromium.org>
74 lines
2.4 KiB
Plaintext
74 lines
2.4 KiB
Plaintext
config DM_SERIAL
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bool "Enable Driver Model for serial drivers"
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depends on DM
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help
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Enable driver model for serial. This replaces
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drivers/serial/serial.c with the serial uclass, which
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implements serial_putc() etc. The uclass interface is
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defined in include/serial.h.
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config DEBUG_UART
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bool "Enable an early debug UART for debugging"
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help
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The debug UART is intended for use very early in U-Boot to debug
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problems when an ICE or other debug mechanism is not available.
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To use it you should:
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- Make sure your UART supports this interface
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- Enable CONFIG_DEBUG_UART
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- Enable the CONFIG for your UART to tell it to provide this interface
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(e.g. CONFIG_DEBUG_UART_NS16550)
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- Define the required settings as needed (see below)
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- Call debug_uart_init() before use
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- Call debug_uart_putc() to output a character
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Depending on your platform it may be possible to use this UART before
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a stack is available.
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If your UART does not support this interface you can probably add
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support quite easily. Remember that you cannot use driver model and
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it is preferred to use no stack.
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You must not use this UART once driver model is working and the
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serial drivers are up and running (done in serial_init()). Otherwise
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the drivers may conflict and you will get strange output.
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choice
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prompt "Select which UART will provide the debug UART"
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depends on DEBUG_UART
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config DEBUG_UART_NS16550
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bool "ns16550"
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help
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Select this to enable a debug UART using the ns16550 driver. You
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will need to provide parameters to make this work. The driver will
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be available until the real driver model serial is running.
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endchoice
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config DEBUG_UART_BASE
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hex "Base address of UART"
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depends on DEBUG_UART
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help
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This is the base address of your UART for memory-mapped UARTs.
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A default should be provided by your board, but if not you will need
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to use the correct value here.
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config DEBUG_UART_CLOCK
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int "UART input clock"
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depends on DEBUG_UART
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help
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The UART input clock determines the speed of the internal UART
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circuitry. The baud rate is derived from this by dividing the input
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clock down.
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A default should be provided by your board, but if not you will need
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to use the correct value here.
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config UNIPHIER_SERIAL
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bool "UniPhier on-chip UART support"
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depends on ARCH_UNIPHIER && DM_SERIAL
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help
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Support for the on-chip UARTs on the Panasonic UniPhier platform.
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