From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759393Ab2EXVQx (ORCPT ); Thu, 24 May 2012 17:16:53 -0400 Received: from wolverine02.qualcomm.com ([199.106.114.251]:6051 "EHLO wolverine02.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758841Ab2EXVQt (ORCPT ); Thu, 24 May 2012 17:16:49 -0400 X-IronPort-AV: E=McAfee;i="5400,1158,6721"; a="192165098" Message-ID: <4FBEA540.1010409@codeaurora.org> Date: Thu, 24 May 2012 14:16:48 -0700 From: Saravana Kannan User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:12.0) Gecko/20120428 Thunderbird/12.0.1 MIME-Version: 1.0 To: Rob Herring CC: Stephen Boyd , Shawn Guo , Mike Turquette , "linux-kernel@vger.kernel.org" , Grant Likely , "arm@kernel.org" , Shawn Guo , "linux-arm-kernel@lists.infradead.org" Subject: Re: [GIT PULL] DT clk binding support References: <4FB80F32.5090309@gmail.com> <20120520030653.GB5810@S2100-06.ap.freescale.net> <4FB9A5E7.2070000@gmail.com> <20120521064901.GE8140@S2101-09.ap.freescale.net> <4FBA89E3.7010106@gmail.com> <20120521232616.GF8140@S2101-09.ap.freescale.net> <4FBAD545.7060803@gmail.com> <20120522021535.GG8140@S2101-09.ap.freescale.net> <4FBB134D.6050409@codeaurora.org> <4FBB9A08.2050803@gmail.com> <49cd509b59c8172c880b0c8a50c0f02c.squirrel@www.codeaurora.org> <4FBCED4D.1040908@gmail.com> In-Reply-To: <4FBCED4D.1040908@gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/23/2012 06:59 AM, Rob Herring wrote: > On 05/22/2012 08:38 PM, Saravana Kannan wrote: >> >> On Tue, May 22, 2012 6:52 am, Rob Herring wrote: >>> On 05/21/2012 11:17 PM, Stephen Boyd wrote: >>>> On 05/21/12 19:15, Shawn Guo wrote: >>>>> On Mon, May 21, 2012 at 06:52:37PM -0500, Rob Herring wrote: >>>>>> As Grant states: "This proposed binding is only about one thing: >>>>>> attaching clock providers to clock consumers." This means you have to >>>>>> have at least a single provider and a single consumer defined in the >>>>>> DT. >>>>>> >>>>> I just read through Grant's comments over again. I agree with the >>>>> statement which implicitly requires the clk provider defined in DT. >>>>> However, for some case, this provider in DT is just a skeleton which >>>>> is backed by clock driver where the provider is actually defined. >>>>> >>>>> Looking at Grant's comment below, the second option is also to match >>>>> the clock in driver just using name. The only difference to my >>>>> proposal is the name here is given by the argument of phandle pointing >>>>> to that skeleton provider node. >>>>> >>>>> I'm fine with that. So go ahead with your bindings. >>>>> >>>> >>>> Can we do what the regulator framework has done and have a common >>>> binding of-clk =<&phandle>? Something like: >>>> >>>> core-clk =<&uart3_clk> >>>> >>>> and then have clk_get() use the of node of the device passed in to find >>>> a property named %s-clk and find the clock with the matching phandle. >>> >>> Sigh... That is what we had in previous versions from over a year ago >>> and we moved away from that approach. The current binding has been >>> reviewed multiple times in the last 6 months... >>> >>> The current approach is aligned with how interrupts are handled (with >>> the addition of a phandle). I think not having per clock property names >>> is easier to parse and easier to document. >>> >>>> This looks like it's trying to cover both the end consumers (uart uses >>>> uart3_clk) and the internal clock tree consumers (a crystal oscillator >>>> connects to a PLL or a mux has multiple parents). We can certainly use >>>> these bindings for muxes and internal parent-child relationships but I >>>> would prefer we use different bindings for consumer bindings that match >>>> what regulators do today. >>> >>> The binding supports either defining every last internal clock or just >>> the leaf clocks. I took the former route on highbank since I don't have >>> a lot of clocks. If I was doing imx or omap for example, I'd probably >>> just define all the clock controller outputs. >>> >> >> If only the leaf nodes are defined in DT, then how is the clock platform >> driver implementer supposed to instantiate the rest of the tree and >> connect it up with the partial list of clocks in DT? So, they have to >> switch back and forth between DT and the .c file which defines the rest >> and make sure the parent<->child names match? >> >> To me it looks that it might better to decouple the description of the >> clock HW from the mapping of a clock leaf to a consumer device. If we just >> use a string to identify the clock that's consumed by a device, we can >> achieve this decoupling at a clean boundary -- clock consumers devices >> (UART) vs clock producer devices (clock controller in the SoC, in a PMIC, >> audio codec, etc). >> >> With the decoupling, we don't have the inconsistency of having some of the >> clocks of a clock producer device incompletely defined in DT and the rest >> of the clocks of the same clock producer device hard coded in the kernel. >> So, you either put your entire clock tree in the SoC in the DT or put all >> of it in the kernel but you aren't forced to put just some of them in the >> DT just to get DT working. I see no benefit in defining only some of the >> clocks in DT -- it just adds more confusion in the clock tree definition. >> What am I missing? > > I fail to see what would need changing in the binding itself. The > binding just describes connections. Whether that is a connection to a > clock controller node to a device or a clock gate/mux/divider node to a > device is really beyond the clock binding. This is really just policy. > You are free to put no clocks in DT, all clocks, or a nexus of clocks. With the current approach you are taking can you please give an example of how a random device described in DT would hook itself up with a leaf clock if that leaf clock is not described in DT? So that it can do a call a DT version of clk_get() to get the clock it cares for. And no, there is a huge difference between binding a clock controller node (by which I mean the block that provides many clocks) to a device vs. binding a clock leaf to a device. The former is useless wrt to clk_get() and similar functions. The latter is very useful to handle that. Thanks, Saravana -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. From mboxrd@z Thu Jan 1 00:00:00 1970 From: skannan@codeaurora.org (Saravana Kannan) Date: Thu, 24 May 2012 14:16:48 -0700 Subject: [GIT PULL] DT clk binding support In-Reply-To: <4FBCED4D.1040908@gmail.com> References: <4FB80F32.5090309@gmail.com> <20120520030653.GB5810@S2100-06.ap.freescale.net> <4FB9A5E7.2070000@gmail.com> <20120521064901.GE8140@S2101-09.ap.freescale.net> <4FBA89E3.7010106@gmail.com> <20120521232616.GF8140@S2101-09.ap.freescale.net> <4FBAD545.7060803@gmail.com> <20120522021535.GG8140@S2101-09.ap.freescale.net> <4FBB134D.6050409@codeaurora.org> <4FBB9A08.2050803@gmail.com> <49cd509b59c8172c880b0c8a50c0f02c.squirrel@www.codeaurora.org> <4FBCED4D.1040908@gmail.com> Message-ID: <4FBEA540.1010409@codeaurora.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 05/23/2012 06:59 AM, Rob Herring wrote: > On 05/22/2012 08:38 PM, Saravana Kannan wrote: >> >> On Tue, May 22, 2012 6:52 am, Rob Herring wrote: >>> On 05/21/2012 11:17 PM, Stephen Boyd wrote: >>>> On 05/21/12 19:15, Shawn Guo wrote: >>>>> On Mon, May 21, 2012 at 06:52:37PM -0500, Rob Herring wrote: >>>>>> As Grant states: "This proposed binding is only about one thing: >>>>>> attaching clock providers to clock consumers." This means you have to >>>>>> have at least a single provider and a single consumer defined in the >>>>>> DT. >>>>>> >>>>> I just read through Grant's comments over again. I agree with the >>>>> statement which implicitly requires the clk provider defined in DT. >>>>> However, for some case, this provider in DT is just a skeleton which >>>>> is backed by clock driver where the provider is actually defined. >>>>> >>>>> Looking at Grant's comment below, the second option is also to match >>>>> the clock in driver just using name. The only difference to my >>>>> proposal is the name here is given by the argument of phandle pointing >>>>> to that skeleton provider node. >>>>> >>>>> I'm fine with that. So go ahead with your bindings. >>>>> >>>> >>>> Can we do what the regulator framework has done and have a common >>>> binding of-clk =<&phandle>? Something like: >>>> >>>> core-clk =<&uart3_clk> >>>> >>>> and then have clk_get() use the of node of the device passed in to find >>>> a property named %s-clk and find the clock with the matching phandle. >>> >>> Sigh... That is what we had in previous versions from over a year ago >>> and we moved away from that approach. The current binding has been >>> reviewed multiple times in the last 6 months... >>> >>> The current approach is aligned with how interrupts are handled (with >>> the addition of a phandle). I think not having per clock property names >>> is easier to parse and easier to document. >>> >>>> This looks like it's trying to cover both the end consumers (uart uses >>>> uart3_clk) and the internal clock tree consumers (a crystal oscillator >>>> connects to a PLL or a mux has multiple parents). We can certainly use >>>> these bindings for muxes and internal parent-child relationships but I >>>> would prefer we use different bindings for consumer bindings that match >>>> what regulators do today. >>> >>> The binding supports either defining every last internal clock or just >>> the leaf clocks. I took the former route on highbank since I don't have >>> a lot of clocks. If I was doing imx or omap for example, I'd probably >>> just define all the clock controller outputs. >>> >> >> If only the leaf nodes are defined in DT, then how is the clock platform >> driver implementer supposed to instantiate the rest of the tree and >> connect it up with the partial list of clocks in DT? So, they have to >> switch back and forth between DT and the .c file which defines the rest >> and make sure the parent<->child names match? >> >> To me it looks that it might better to decouple the description of the >> clock HW from the mapping of a clock leaf to a consumer device. If we just >> use a string to identify the clock that's consumed by a device, we can >> achieve this decoupling at a clean boundary -- clock consumers devices >> (UART) vs clock producer devices (clock controller in the SoC, in a PMIC, >> audio codec, etc). >> >> With the decoupling, we don't have the inconsistency of having some of the >> clocks of a clock producer device incompletely defined in DT and the rest >> of the clocks of the same clock producer device hard coded in the kernel. >> So, you either put your entire clock tree in the SoC in the DT or put all >> of it in the kernel but you aren't forced to put just some of them in the >> DT just to get DT working. I see no benefit in defining only some of the >> clocks in DT -- it just adds more confusion in the clock tree definition. >> What am I missing? > > I fail to see what would need changing in the binding itself. The > binding just describes connections. Whether that is a connection to a > clock controller node to a device or a clock gate/mux/divider node to a > device is really beyond the clock binding. This is really just policy. > You are free to put no clocks in DT, all clocks, or a nexus of clocks. With the current approach you are taking can you please give an example of how a random device described in DT would hook itself up with a leaf clock if that leaf clock is not described in DT? So that it can do a call a DT version of clk_get() to get the clock it cares for. And no, there is a huge difference between binding a clock controller node (by which I mean the block that provides many clocks) to a device vs. binding a clock leaf to a device. The former is useless wrt to clk_get() and similar functions. The latter is very useful to handle that. Thanks, Saravana -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.