Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755149Ab3DKJFH (ORCPT ); Thu, 11 Apr 2013 05:05:07 -0400 Received: from devils.ext.ti.com ([198.47.26.153]:52729 "EHLO devils.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754474Ab3DKJFA (ORCPT ); Thu, 11 Apr 2013 05:05:00 -0400 Message-ID: <51667C9D.8080409@ti.com> Date: Thu, 11 Apr 2013 12:04:29 +0300 From: Grygorii Strashko User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130308 Thunderbird/17.0.4 MIME-Version: 1.0 To: Roger Quadros CC: Nishanth Menon , Mike Turquette , Tony Lindgren , , , , , , , Subject: Re: [RFC][PATCH 1/2] ARM: OMAP4: clock: Add device tree support for AUXCLKs References: <515D2D30.3000306@ti.com> <20130404164137.GH10155@atomide.com> <515EA9E3.1010409@ti.com> <20130405155851.GA10155@atomide.com> <5163E589.1040809@ti.com> <20130409164928.GL10155@atomide.com> <20130409174319.GP10155@atomide.com> <20130409204900.GA8815@kahuna> <20130410080630.14359.68178@quantum> <5165453E.6090503@ti.com> <20130410173921.GA31017@kahuna> <51666AE8.9060602@ti.com> In-Reply-To: <51666AE8.9060602@ti.com> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.167.145.172] X-EXCLAIMER-MD-CONFIG: f9c360f5-3d1e-4c3c-8703-f45bf52eff6b Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 12107 Lines: 312 On 04/11/2013 10:48 AM, Roger Quadros wrote: > On 04/10/2013 08:39 PM, Nishanth Menon wrote: >> On 13:55-20130410, Roger Quadros wrote: >>> On 04/10/2013 11:06 AM, Mike Turquette wrote: >>>> Quoting Nishanth Menon (2013-04-09 13:49:00) >>>>> On 10:43-20130409, Tony Lindgren wrote: >>>>>> * Tony Lindgren [130409 09:54]: >>>>>>> * Roger Quadros [130409 03:00]: >>>>>>>> On 04/05/2013 06:58 PM, Tony Lindgren wrote: >>>>>>>>> Can't you just use the clock name there to get it? >>>>>>>> In device tree we don't pass around clock names. You can either get >>>>>>>> a phandle or an index to the clock. >>>>>>>> >>>>>>>> e.g. Documentation/devicetree/bindings/clock/imx31-clock.txt >>>>>>> Yes I understand that. But the driver/clock/omap driver can just >>>>>>> remap the DT device initially so the board specific clock is >>>>>>> found from the clock alias table. Basically initially a passthrough >>>>>>> driver that can be enhanced to parse DT clock bindings and load >>>>>>> data from /lib/firmware. >>>>>> Actually probably the driver/clock/omap can even do even less >>>>>> initially. There probably even no need to remap clocks there. >>>>>> >>>>>> As long as the DT clock driver understands that a board specific >>>>>> auxclk is specified in the DT it can just call clk_add_alias() so >>>>>> the driver will get the right auxclk from cclock44xx_data.c. >>>>>> >>>>>> Then other features can be added later on like to allocate a >>>>>> clock entirely based on the binding etc. >>>>> I did try to have an implementation for cpufreq using clock nodes. >>>>> unfortunately, device tree wont let me have arguments of strings :( >>>>> So, I am unable to do clock = <&clk mpu_dpll>; >>>>> instead, I am forced to do clock = <&clk 249>; >>>>> >>>> See http://article.gmane.org/gmane.linux.ports.arm.kernel/229034 >>>> >>> Awesome. Thanks for pointing this out Mike. >>> >>> Now all we need to do is create a named define for each clock index in the >>> header file. >> Approach #3: Thanks to Tony for collaborating on this: >> Works for cpufreq-cpu0 - additional patches: >> http://pastebin.com/GHnTRVJf, http://pastebin.com/FZS89J6L (tested on >> beagleXM) >> Work for USB - http://pastebin.com/aJpDnXci - thanks Roger for testing >> this. >> Details in the patch below (Tony, I have added you as collaborator for >> helping in getting this working-clk_add_alias was'nt needed in the >> internal patch discussion we had - I have taken a bit of freedom in >> adding your contributions to the patch below) >> >> Folks, this does seem to be the best compromise we can achieve at this >> point in time. feedback on this approach is much appreciated - if folks >> are ok, I can post this as an formal patch series. > This looks fine to me. Minor comments below. I like it. No IDs and can add clocks support in DT as needed. > >> From 130a41821bf57081ca45ef654029175d173135e6 Mon Sep 17 00:00:00 2001 >> From: Nishanth Menon >> Date: Tue, 9 Apr 2013 19:26:40 -0500 >> Subject: [RFC PATCH] clk: OMAP: introduce device tree binding to kernel clock >> data >> >> OMAP clock data is located in arch/arm/mach-omap2/cclockXYZ_data.c. >> However, this presents an obstacle for using these clock nodes in >> Device Tree definitions. There are many possible approaches to this >> problem as discussed in the following thread: >> http://marc.info/?t=136370325600009&r=1&w=2 >> Highlights of the options: >> a) device specific clk_add_alias: >> cons: driver handling required >> b) using an generic clk node and indexing to reach the clock required. >> This is similar in approach taken by tegra and few other platforms. >> example clock = <&clk 5>; >> cons: potential to have mismatches in indexed table and associated >> dtb data. In addition, managing continued documentation in bindings >> as clock indexing increases. Even though readability angle could be >> improved by using preprocessing of DT using macros, indexed approach >> is inherently risky from cases like the following: >> clk indexes in kernel: >> 1 - mpu_dpll >> 2 - aux_clk1 >> 3 - core_clk >> DT entry for peripheral x uses <&clk 2>, kernel updates to: >> 1 - mpu_dpll >> 2 - per_dpll >> 3 - aux_clk1 >> 4 - core_clk >> using the old dtb(or dts missing an update), on new kernel which has >> updated indices will result in per_dpll now controlled for peripheral >> X without warning or any potential error detection and warning. >> >> Even though we can claim this is user error, such errors are hard to >> track down and fix. >> >> An alternate approach introduced here is to introduce device tree bindings >> corresponding to the clock nodes required in DT definition for SoC which >> automatically maps back to the definitions in cclockXYZ_data.c. >> >> The driver introduced here to do this mapping will eventually be the >> place where the clock handling will migrate to. We need to consider this >> angle as well so that the solution will be an valid transition point for >> moving the clock data out of kernel image (into device tree or firmware load >> etc..). >> >> Overall strategy introduced here is simple: an clock node described in > typo: "an"->"a" > >> device tree blob is used to identify the exact clock provided in the SoC >> specific data. This is then linked back using of_clk_add_provider to the >> device node to be accessible by of_clk_get. >> >> Based on discussion contributions from Roger Quadros, Grygorii Strashko >> and others. >> >> [tony@atomide.com: co-developed] >> Signed-off-by: Tony Lindgren >> Signed-off-by: Nishanth Menon >> --- >> .../devicetree/bindings/clock/omap-clock.txt | 40 +++++++++ >> drivers/clk/Makefile | 1 + >> drivers/clk/omap/Makefile | 1 + >> drivers/clk/omap/clk.c | 94 ++++++++++++++++++++ >> 4 files changed, 136 insertions(+) >> create mode 100644 Documentation/devicetree/bindings/clock/omap-clock.txt >> create mode 100644 drivers/clk/omap/Makefile >> create mode 100644 drivers/clk/omap/clk.c >> >> diff --git a/Documentation/devicetree/bindings/clock/omap-clock.txt b/Documentation/devicetree/bindings/clock/omap-clock.txt >> new file mode 100644 >> index 0000000..07e3ff8 >> --- /dev/null >> +++ b/Documentation/devicetree/bindings/clock/omap-clock.txt >> @@ -0,0 +1,40 @@ >> +Device Tree Clock bindings for Texas Instrument's OMAP compatible platforms >> + >> +This binding is a work-in-progress, and meant to be stage #1 of transitioning >> +OMAP clock data out of kernel image. >> + >> +This binding uses the common clock binding[1]. >> + >> +[1] Documentation/devicetree/bindings/clock/clock-bindings.txt >> + >> +Required properties: >> +- compatible : shall be "ti,omap-clock" >> +- #clock-cells : from common clock binding; shall be set to 0. >> +NOTE: >> +node name should map to clock database in arch/arm/mach-omap2/cclock_data.c >> +Since all clocks are described with _ck, the node name is optimized to drop the >> +usage of _ck. For example, a clock called dpll1_ck will be defined as dpll1. >> + >> +Example #1: describing clock node for CPU on OMAP34xx platform: >> +Ref: arch/arm/mach-omap2/cclock3xxx_data.c >> +describes the CPU clock to be as follows >> + CLK(NULL, "dpll1_ck", &dpll1_ck, CK_3XXX), >> +Corresponding binding will be: >> + dpll1: dpll1 { >> + #clock-cells = <0>; >> + compatible = "ti,omap-clock"; >> + }; >> +And it's usage will be: >> + clocks = <&dpll1>; >> + >> +Example #2: describing clock node for auxilary clock #3 on OMAP443x platform: >> +Ref: arch/arm/mach-omap2/cclock44xx_data.c >> +describes the auxclk3 clock to be as follows: >> + CLK(NULL, "auxclk3_ck", &auxclk3_ck, CK_443X), >> +Corresponding binding will be: >> + auxclk3: auxclk3 { >> + #clock-cells = <1>; >> + compatible = "ti,omap-clock"; >> + }; >> +And it's usage will be: >> + clocks = <&auxclk3>; >> diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile >> index 300d477..a0209d7 100644 >> --- a/drivers/clk/Makefile >> +++ b/drivers/clk/Makefile >> @@ -27,6 +27,7 @@ obj-$(CONFIG_ARCH_U8500) += ux500/ >> obj-$(CONFIG_ARCH_VT8500) += clk-vt8500.o >> obj-$(CONFIG_ARCH_ZYNQ) += clk-zynq.o >> obj-$(CONFIG_ARCH_TEGRA) += tegra/ >> +obj-$(CONFIG_ARCH_OMAP) += omap/ >> >> obj-$(CONFIG_X86) += x86/ >> >> diff --git a/drivers/clk/omap/Makefile b/drivers/clk/omap/Makefile >> new file mode 100644 >> index 0000000..8195931 >> --- /dev/null >> +++ b/drivers/clk/omap/Makefile >> @@ -0,0 +1 @@ >> +obj-y += clk.o >> diff --git a/drivers/clk/omap/clk.c b/drivers/clk/omap/clk.c >> new file mode 100644 >> index 0000000..63a4cce >> --- /dev/null >> +++ b/drivers/clk/omap/clk.c >> @@ -0,0 +1,94 @@ >> +/* >> + * Texas Instruments OMAP Clock driver >> + * >> + * Copyright (C) 2013 Texas Instruments Incorporated - http://www.ti.com/ >> + * Nishanth Menon > missing e-mail id. > >> + * Tony Lindgren >> + * >> + * This program is free software; you can redistribute it and/or modify >> + * it under the terms of the GNU General Public License version 2 as >> + * published by the Free Software Foundation. >> + * >> + * This program is distributed "as is" WITHOUT ANY WARRANTY of any >> + * kind, whether express or implied; without even the implied warranty >> + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the >> + * GNU General Public License for more details. >> + */ >> + >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> + >> +static const struct of_device_id omap_clk_of_match[] = { >> + {.compatible = "ti,omap-clock",}, >> + {}, >> +}; >> + >> +MODULE_DEVICE_TABLE(of, omap_clk_of_match); >> + > Is this driver ever going to be a loadable module? If not then you don't need this. > >> +/** >> + * omap_clk_probe() - create link from DT definition to clock data >> + * @pdev: device node >> + * >> + * REVISIT: We are now assuming the following: >> + * 1. omap clock names end with _ck >> + * 2. omap clocks don't get removed >> + */ >> +static int omap_clk_probe(struct platform_device *pdev) >> +{ >> + struct clk *clk; >> + int res; >> + >> + const struct of_device_id *match; >> + struct device_node *np = pdev->dev.of_node; >> + char clk_name[32]; >> + >> + match = of_match_device(omap_clk_of_match, &pdev->dev); >> + >> + /* Set up things so consumer can call clk_get() with name */ >> + snprintf(clk_name, 32, "%s_ck", np->name); >> + clk = clk_get(NULL, clk_name); >> + if (IS_ERR(clk)) { >> + res = PTR_ERR(clk); >> + dev_err(&pdev->dev, "could not get clock %s (%d)\n", >> + clk_name, res); >> + goto out; >> + } >> + >> + /* This allows the driver to of_clk_get() */ >> + res = of_clk_add_provider(np, of_clk_src_simple_get, clk); >> + if (res) >> + dev_err(&pdev->dev, "could not add provider for %s (%d)\n", >> + clk_name, res); >> + >> + clk_put(clk); >> +out: >> + return res; >> +} >> + >> +MODULE_ALIAS("platform:omap_clk"); > ditto. > >> + >> +/* We assume here that OMAP clocks will not be removed */ >> +static struct platform_driver omap_clk_driver = { >> + .probe = omap_clk_probe, >> + .driver = { >> + .name = "omap_clk", >> + .owner = THIS_MODULE, > same here. > >> + .of_match_table = of_match_ptr(omap_clk_of_match), >> + }, >> +}; >> + >> +static int __init omap_clk_init(void) >> +{ >> + return platform_driver_register(&omap_clk_driver); >> +} >> + >> +arch_initcall(omap_clk_init); >> + >> +MODULE_DESCRIPTION("OMAP Clock driver"); >> +MODULE_AUTHOR("Texas Instruments Inc."); >> +MODULE_LICENSE("GPL v2"); >> > cheers, > -roger -grygorii -- 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/