From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Walleij Subject: Re: [v5 1/2] dt-bindings: gpio: aspeed: Add SGPIO support Date: Mon, 29 Jul 2019 23:57:16 +0200 Message-ID: References: <1563564291-9692-1-git-send-email-hongweiz@ami.com> <1563564291-9692-2-git-send-email-hongweiz@ami.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Andrew Jeffery Cc: Hongwei Zhang , "open list:GPIO SUBSYSTEM" , Joel Stanley , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , linux-aspeed , Bartosz Golaszewski , Rob Herring , Mark Rutland , "linux-kernel@vger.kernel.org" , Linux ARM List-Id: devicetree@vger.kernel.org On Mon, Jul 29, 2019 at 2:19 AM Andrew Jeffery wrote: > The behaviour is to periodically emit the state of all enabled GPIOs > (i.e. the ngpios value), one per bus clock cycle. There's no explicit > addressing scheme, the protocol encodes the value for a given GPIO > by its position in the data stream relative to a pulse on the "load data" > (LD) line, whose envelope covers the clock cycle for the last GPIO in > the sequence. Similar to SPI the bus has both out and in lines, which > cater to output/input GPIOs. > > A rough timing diagram for a 16-GPIO configuration looks like what > I've pasted here: > > https://gist.github.com/amboar/c9543af1957854474b8c05ab357f0675 OK that is complex. I agree we need to keep this driver together. Yours, Linus Walleij