From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mirza Krak Subject: Re: [RFC 3/6] dt/bindings: Add bindings for Tegra20/30 NOR bus driver Date: Mon, 25 Jul 2016 21:59:34 +0200 Message-ID: References: <1468935397-11926-1-git-send-email-mirza.krak@gmail.com> <1468935397-11926-4-git-send-email-mirza.krak@gmail.com> <20160725113034.GD21170@ulmo.ba.sec> <20160725141544.GN21170@ulmo.ba.sec> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: In-Reply-To: <20160725141544.GN21170@ulmo.ba.sec> Sender: linux-clk-owner@vger.kernel.org To: Thierry Reding Cc: Stephen Warren , Alexandre Courbot , pdeschrijver@nvidia.com, Prashant Gaikwad , Michael Turquette , sboyd@codeaurora.org, devicetree@vger.kernel.org, linux-tegra@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org, robh+dt@kernel.org, pawel.moll@arm.com, mark.rutland@arm.com, ijc+devicetree@hellion.org.uk, Kumar Gala , linux@armlinux.org.uk List-Id: linux-tegra@vger.kernel.org 2016-07-25 16:15 GMT+02:00 Thierry Reding : > On Mon, Jul 25, 2016 at 03:16:28PM +0200, Mirza Krak wrote: >> 2016-07-25 13:30 GMT+02:00 Thierry Reding : >> > >> > I would've expected this to require some sort of infrastructure to allow >> > devices connected to the GMI controller to acquire the bus via some API >> > to select their chip. >> >> Yes, ultimately you would need some sort of infrastructure to allow >> devices to acquire the GMI bus if you want to solve this in software. >> But at the moment I do not see such an infrastructure in place, and is >> it feasible to add one specifically for the GMI controller? If one >> such infrastructure was in place we would need to modify all the >> drivers that want to use to include Tegra specific infrastructure to >> access the GMI bus? >> >> Since my knowledge is limited it hard for me to comment on this, maybe >> there is a simple way of doing this? > > I don't think there's a simple way to do this. In order to properly > implement it we'd need to implement a generic infrastructure for chip > selects so that drivers such as the one for your CAN controller can be > written without tying them specifically to the Tegra GMI controller. > > From what you and Jon were saying it sounds like the drivers are > completely agnostic of any chip-select, so conversion won't be easy. > But technically if these chips take a chip-select as input then it's > always possible to hook them up to a controller that doesn't do this > automatic translation of address to chip-select, so eventually some > setup is bound to come along where they'd need explicit chip-select > handling as well. > > I don't think it's fair to require you to implement this infrastructure > if you don't actually need it. At the same time I want to be cautious > and make sure we keep the driver and binding flexible enough to allow > us to implement explicit chip-selects should we later need them. > > Thierry One thing that should be noted, and that is the GMI controller also supports a DMA master mode (feature for the future?). I do not really know how this effects the binding we are discussing but wanted to put it out there. Best Regards, Mirza From mboxrd@z Thu Jan 1 00:00:00 1970 From: mirza.krak@gmail.com (Mirza Krak) Date: Mon, 25 Jul 2016 21:59:34 +0200 Subject: [RFC 3/6] dt/bindings: Add bindings for Tegra20/30 NOR bus driver In-Reply-To: <20160725141544.GN21170@ulmo.ba.sec> References: <1468935397-11926-1-git-send-email-mirza.krak@gmail.com> <1468935397-11926-4-git-send-email-mirza.krak@gmail.com> <20160725113034.GD21170@ulmo.ba.sec> <20160725141544.GN21170@ulmo.ba.sec> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 2016-07-25 16:15 GMT+02:00 Thierry Reding : > On Mon, Jul 25, 2016 at 03:16:28PM +0200, Mirza Krak wrote: >> 2016-07-25 13:30 GMT+02:00 Thierry Reding : >> > >> > I would've expected this to require some sort of infrastructure to allow >> > devices connected to the GMI controller to acquire the bus via some API >> > to select their chip. >> >> Yes, ultimately you would need some sort of infrastructure to allow >> devices to acquire the GMI bus if you want to solve this in software. >> But at the moment I do not see such an infrastructure in place, and is >> it feasible to add one specifically for the GMI controller? If one >> such infrastructure was in place we would need to modify all the >> drivers that want to use to include Tegra specific infrastructure to >> access the GMI bus? >> >> Since my knowledge is limited it hard for me to comment on this, maybe >> there is a simple way of doing this? > > I don't think there's a simple way to do this. In order to properly > implement it we'd need to implement a generic infrastructure for chip > selects so that drivers such as the one for your CAN controller can be > written without tying them specifically to the Tegra GMI controller. > > From what you and Jon were saying it sounds like the drivers are > completely agnostic of any chip-select, so conversion won't be easy. > But technically if these chips take a chip-select as input then it's > always possible to hook them up to a controller that doesn't do this > automatic translation of address to chip-select, so eventually some > setup is bound to come along where they'd need explicit chip-select > handling as well. > > I don't think it's fair to require you to implement this infrastructure > if you don't actually need it. At the same time I want to be cautious > and make sure we keep the driver and binding flexible enough to allow > us to implement explicit chip-selects should we later need them. > > Thierry One thing that should be noted, and that is the GMI controller also supports a DMA master mode (feature for the future?). I do not really know how this effects the binding we are discussing but wanted to put it out there. Best Regards, Mirza