[RFC] Using two baud rate generators with the cpm_uart driver

[Laurent Pinchart <laurentp@cse-semaphore.com>]

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Hi everybody,

thanks to a bad hardware design decision, I'm faced with a software issue with 
the cpm_uart driver.

My hardware uses either SCC4 or SMC2 (production-time option) as an RS485 port 
with an external transceiver. The transceiver's data direction is controlled 
by external logic that monitors the SCC4/SMC2 TxD signal.

The external logic needs an input clock at the baud rate frequency on the 
MPC8248 BRG5 output pin (although I could modify it to accept an input clock 
at 16x the baud rate frequency). This means the cpm_uart driver has to setup 
two baud rate generators instead of one.

The ppc architecture was easy to hack as it used a fs_uart_platform_info 
structure in which I added a set_brg function pointer provided by platform 
code. This isn't possible with the powerpc architecture anymore.

Is there a clean way to fix this issue ? Kicking the hardware designer won't 
help :-)

Best regards,

-- 
Laurent Pinchart
CSE Semaphore Belgium

Chaussee de Bruxelles, 732A
B-1410 Waterloo
Belgium

T +32 (2) 387 42 59
F +32 (2) 387 42 75

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