ChangeLog v1: This series of patches add support to FIFOs which will be introduced with Atmel sama5d2x SoC. FIFOs allow to reduce the number of I/O access. Indeed depending on the data size and the USART mode, FIFOs work in either single or multiple data. For multiple data, up to 4 data can be written into the Transmit Holding Register or read from the Receive Holding Register in a single word access. Also the RX FIFO allows to reduce the risk of receive overrun and data loss, especially when the DMA controller is not used. Finally, when the hardware handshake mode is selected, the RTS line can now be controlled by two thresholds on the RX FIFO. When FIFO level (the number of data available to be read) crosses the high threshold, the RTS line is set to high level telling the peer that it should stop sending new data. Data are read from the RX FIFO and when the FIFO level crosses the low threshold, the RTS is set back to low level telling the remote peer that it can send data again. This new feature resolves a long time hardware limitation where the RTS line was directly controlled by a PDC signal. There is no equivalent of that signal for the DMA controller so for all SoCs without PDC for USART there was no mean to control the RTS line properly: once the hardware handshake mode selected, the RTS line remains high level. Next SoCs with FIFOs will be able to use the hardware handshake mode thanks to the RX FIFO. Cyrille Pitchen (4): ARM: at91/dt: add new DT properties for Atmel usart tty/serial: at91: fix some macro definitions to fit coding style tty/serial: at91: add support to FIFOs tty/serial: at91: use 32bit writes into TX FIFO when DMA is enabled .../devicetree/bindings/serial/atmel-usart.txt | 15 ++ drivers/tty/serial/atmel_serial.c | 195 +++++++++++++---- include/linux/atmel_serial.h | 240 ++++++++++++--------- 3 files changed, 307 insertions(+), 143 deletions(-) -- 1.8.2.2 -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
