tree 8bb849de9ccaf8e73e97e88debdc9ee0ae332ff4
parent 62c37eedb74c8fbf3c92f8f28a871e6bd80c181a
author Robert Baldyga <r.baldyga@samsung.com> 1418212166 +0100
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1420842339 -0800

serial: samsung: add DMA support for TX

Add TX DMA transfers support for samsung serial driver. It's enabled
when "dmas" property is defined in serial device-tree node, otherwise
TX transfers are prerformed using PIO.

TX DMA is used for data segments larger than fifosize to reduce number
of interrupts during data transmission. For buffers shorter than fifosize
PIO mode is selected.

Data blocks for DMA transfers are aligned to cache line size to avoid
problems with coherency (some areas of TX circ buffer can be used by
CPU during DMA transaction, so we have to ensure that our data is always
consistent).

Based on previous work of Sylwester Nawrocki and Lukasz Czerwinski.

Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>