atmel_serial: Use the fractional divider when possible
The fractional baud rate generator is available when using the asynchronous mode of Atmel USART controllers. It makes it possible to use higher baudrates, in exchange for a less precise clock with a variable duty cycle. The existing code restricts its use to the normal mode of the USART controller, following the recommendation from the datasheet for the first chip embedding this type of controller. This recommendation has been removed from the documentation for the newer chips. After verification, all revisions of this controller should be able to use the fractional baud rate generator with the different asynchronous modes. Removing the condition on ATMEL_US_USMODE makes it possible to get correct baudrates at high speed in more cases. This was tested with a board using an Atmel SAMA5D2 chip and a TI WL1831 WiFi/Bluetooth combo chip at 3 Mbauds, with hardware flow control enabled. Signed-off-by:Romain Izard <romain.izard.pro@gmail.com> Acked-by:
Ludovic Desroches <ludovic.desroches@microchip.com> Signed-off-by:
Richard Genoud <richard.genoud@gmail.com> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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6d35b131
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