x86: Enable debug UART for Minnowmax
Enable the debug UART and emit a single 'a' early in the init sequence to show that it is working. Unfortunately the debug UART implementation needs a stack to work. I cannot seem to remove this limitation as the absolute 'jmp %eax' instruction goes off into the weeds. So this means that the character output cannot be any earlier than car_init_ret, where memory is available for a stack. Signed-off-by: Simon Glass <sjg@chromium.org> Reviewed-by: Lukasz Majewski <l.majewski@samsung.com>
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@ -128,6 +128,15 @@ car_init_ret:
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andl $0xfffffff0, %esp
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post_code(POST_START_STACK)
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/*
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* Debug UART is available here although it may not be plumbed out
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* to pins depending on the board. To use it:
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*
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* call debug_uart_init
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* mov $'a', %eax
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* call printch
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*/
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/* Zero the global data since it won't happen later */
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xorl %eax, %eax
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movl $GENERATED_GBL_DATA_SIZE, %ecx
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@ -24,3 +24,7 @@ CONFIG_FRAMEBUFFER_VESA_MODE_11A=y
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CONFIG_DM_RTC=y
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CONFIG_USE_PRIVATE_LIBGCC=y
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CONFIG_SYS_VSNPRINTF=y
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CONFIG_DEBUG_UART=y
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CONFIG_DEBUG_UART_NS16550=y
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CONFIG_DEBUG_UART_BASE=0x3f8
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CONFIG_DEBUG_UART_CLOCK=1843200
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