serial: 8250_dw: Do not bailout on UCV read returning zero

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Designware UART has optional feature FIFO_MODE to implement FIFO.
Encoding FIFO capabilities through Component Parameter Register CPR is
optional and it can be enabled using parameter UART_ADD_ENCODED_PARAMS.

Driver can exercise fifo capabilities by decoding CPR if implemented
or from cpr_val provided from the dw8250_platform_data otherwise.

dw8250_setup_port() checks for CPR or cpr_val to determine FIFO size
only when Component Version (UCV) is non-zero. Bailing out early on UCV
read returning zero will leave fifosize as zero and !UART_CAP_FIFO,
hence prevent early return and continue to process CPR or cpr_val for
the driver to utilize FIFO.

Non-zero UCV implies ADDITIONAL_FEATURES=1, preventing early return
will not be an overhead here.

Signed-off-by: Vamshi Gajjela <vamshigajjela@google.com>
Link: https://lore.kernel.org/r/20231231182951.877805-1-vamshigajjela@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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Vamshi Gajjela 2023-12-31 23:59:51 +05:30 • committed by Greg Kroah-Hartman

parent 7c45eaa813

commit d8a0284479

1 changed files with 3 additions and 9 deletions

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drivers/tty/serial/8250/8250_dwlib.c

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