Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757546AbbFPKJq (ORCPT ); Tue, 16 Jun 2015 06:09:46 -0400 Received: from eusmtp01.atmel.com ([212.144.249.243]:35801 "EHLO eusmtp01.atmel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757527AbbFPKJi (ORCPT ); Tue, 16 Jun 2015 06:09:38 -0400 From: Cyrille Pitchen To: , , CC: , , , , , , , , Cyrille Pitchen Subject: [PATCH v4 1/2] spi: atmel: update DT bindings documentation Date: Tue, 16 Jun 2015 12:09:30 +0200 Message-ID: <9e81a46cea33e9c566f823200fda980ae1710906.1434448837.git.cyrille.pitchen@atmel.com> X-Mailer: git-send-email 1.8.2.2 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2713 Lines: 67 - 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 --- 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 4f8184d..fb588b3 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 { -- 1.8.2.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/