From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcus Weseloh Subject: [PATCH] spi: dts: sun4i: Add support for inter-word wait cycles Date: Thu, 19 Nov 2015 16:53:41 +0100 Message-ID: <1447948422-4915-1-git-send-email-mweseloh42@gmail.com> Reply-To: mweseloh42-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Cc: Marcus Weseloh , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Maxime Ripard , Mark Brown , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: linux-sunxi-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org Return-path: List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , List-Id: linux-spi.vger.kernel.org Hi all, the Allwinner A10/A20 SPI module supports an option to configure a number of clock periods to wait between each word ("SPI Wait Clock Register" in the A20 manual). This is a very useful option if talking to devices which specify a minimum amount of inter-word wait time. I initially tried to find a way to let SPI protocol drivers specify this option, but I couldn't find a mechanism to pass additional options to the spi master. So I took the spi-davinci driver as an example (it implements a very similiar functionality) and added a new devicetree property. While testing this patch I noticed that the SPI module always adds a constant 3 clock cycles to the number set in the Wait Clock Register. That number stays constant across many different baud rates, so I documented it in the devicetree binding file. One thing I am unsure of is the device example in the binding documentation. I used "example,dummy" as compatible... is this acceptable or should I use a device/compatible that actually exists somewhere? Oh... and should I split binding documentation and code changing patch? Best regards, Marcus Marcus Weseloh (1): spi: dts: sun4i: Add support for inter-word wait cycles using the SPI Wait Clock Register Documentation/devicetree/bindings/spi/spi-sun4i.txt | 11 +++++++++++ drivers/spi/spi-sun4i.c | 7 +++++++ 2 files changed, 18 insertions(+) -- 1.9.1