At present on x86 machines with use cache-as-RAM, the memory goes away just
before board_init_r() is called. This means that serial drivers are
no-longer unavailable, until initr_dm() it called, etc.
Any attempt to use printf() within this period will cause a hang.
To fix this, mark the serial devices as 'unavailable' when it is no-longer
available. Bring it back when serial_initialize() is called. This means that
the debug UART will be used instead for this period.
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
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