tree 821f601bd0008681a9ac7e369084af0292166924
parent 6719693ca2efb0f04654d05768ee299e87e1694b
author Cyrille Pitchen <cyrille.pitchen@atmel.com> 1435843089 +0200
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1437699642 -0700

ARM: at91/dt: add a new DT property to support FIFOs on Atmel USARTs

This patch adds a new DT property, "atmel,fifo-size", to enable and set
the maximum number of data the RX and TX FIFOs can store on FIFO capable
USARTs.

Please be aware that the VERSION register can not be used to guess the
size of FIFOs. Indeed, for a given hardware version, the USARTs can be
integrated on Atmel SoCs with different FIFO sizes. Also the
"atmel,fifo-size" property is optional as older USARTs don't embed FIFO at
all.

Besides, the FIFO size can not be read or guessed from other registers:
When designing the FIFO feature, no dedicated registers were added to
store this size. Unsed spaces in the I/O register range are limited and
better reserved for future usages. Instead, the FIFO size of each
peripheral is documented in the programmer datasheet.

Finally, on a given SoC, there can be several instances of USART with
different FIFO sizes. This explain why we'd rather use a dedicated DT
property than use the "compatible" property.

Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>