From 2c01a3d6b3cf0aaf39b55318fd986b1bd0b98168 Mon Sep 17 00:00:00 2001 From: Cyrille Pitchen Date: Tue, 16 Jun 2015 12:09:30 +0200 Subject: [PATCH] spi: atmel: update DT bindings documentation - add new property "atmel,fifo-size" - change "cs-gpios" to optional for SPI controller version >= 2. Please be aware that the VERSION register can not be used to guess the size of FIFOs. Indeed, for a given hardware version, the SPI controller can be integrated on Atmel SoCs with different FIFO sizes. Also the "atmel,fifo-size" property is optional as older SPI controllers 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. Unused 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 the SPI controller with different FIFO sizes. This explain why we'd rather use a dedicated DT property than use the "compatible" property. For instance, sama5d2x SoCs come with some SPI controllers, the ones inside Flexcoms, integrating 32 data FIFOs whereas other SPI controllers use 16 data FIFOs. All these SPI controllers share the same IP version. Signed-off-by: Cyrille Pitchen Acked-by: Nicolas Ferre Signed-off-by: Mark Brown --- Documentation/devicetree/bindings/spi/spi_atmel.txt | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/Documentation/devicetree/bindings/spi/spi_atmel.txt b/Documentation/devicetree/bindings/spi/spi_atmel.txt index 4f8184d069cb..fb588b3e6a9a 100644 --- a/Documentation/devicetree/bindings/spi/spi_atmel.txt +++ b/Documentation/devicetree/bindings/spi/spi_atmel.txt @@ -4,11 +4,16 @@ Required properties: - compatible : should be "atmel,at91rm9200-spi". - reg: Address and length of the register set for the device - interrupts: Should contain spi interrupt -- cs-gpios: chipselects +- cs-gpios: chipselects (optional for SPI controller version >= 2 with the + Chip Select Active After Transfer feature). - clock-names: tuple listing input clock names. Required elements: "spi_clk" - clocks: phandles to input clocks. +Optional properties: +- atmel,fifo-size: maximum number of data the RX and TX FIFOs can store for FIFO + capable SPI controllers. + Example: spi1: spi@fffcc000 { @@ -20,6 +25,7 @@ spi1: spi@fffcc000 { clocks = <&spi1_clk>; clock-names = "spi_clk"; cs-gpios = <&pioB 3 0>; + atmel,fifo-size = <32>; status = "okay"; mmc-slot@0 { -- 2.20.1