Most litex boards using RISC-V soft cores us the sbi earlycon, however
this is not available for non RISC-V litex SoC's.  This patch enables
earlycon for liteuart which is available on all Litex SoC's making
support for earycon debugging more widely available.

Cc: Florent Kermarrec <florent@enjoy-digital.fr>
Cc: Mateusz Holenko <mholenko@antmicro.com>
Cc: Joel Stanley <joel@jms.id.au>
Cc: Gabriel L. Somlo <gsomlo@gmail.com>
Reviewed-and-tested-by: Gabriel Somlo <gsomlo@gmail.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Stafford Horne <shorne@gmail.com>
Link: https://lore.kernel.org/r/20210517115453.24365-1-shorne@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

In case of error, the function devm_platform_get_and_ioremap_resource()
returns ERR_PTR() and never returns NULL. The NULL test in the return
value check should be replaced with IS_ERR().

Fixes: 1da81e5562fa ("drivers/tty/serial: add LiteUART driver")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Link: https://lore.kernel.org/r/20210305034929.3234352-1-weiyongjun1@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This commit adds driver for the FPGA-based LiteUART serial controller
from LiteX SoC builder.

The current implementation supports LiteUART configured
for 32 bit data width and 8 bit CSR bus width.

It does not support IRQ.

Signed-off-by: Filip Kokosinski <fkokosinski@antmicro.com>
Signed-off-by: Mateusz Holenko <mholenko@antmicro.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stafford Horne <shorne@gmail.com>