Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932598Ab3HGRm5 (ORCPT ); Wed, 7 Aug 2013 13:42:57 -0400 Received: from avon.wwwdotorg.org ([70.85.31.133]:53837 "EHLO avon.wwwdotorg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932071Ab3HGRmy (ORCPT ); Wed, 7 Aug 2013 13:42:54 -0400 Message-ID: <52028719.8070908@wwwdotorg.org> Date: Wed, 07 Aug 2013 11:42:49 -0600 From: Stephen Warren User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130510 Thunderbird/17.0.6 MIME-Version: 1.0 To: Viresh Kumar CC: rjw@sisk.pl, swarren@nvidia.com, linaro-kernel@lists.linaro.org, patches@linaro.org, cpufreq@vger.kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, mturquette@linaro.org, linux-arm-kernel@lists.infradead.org, "devicetree@vger.kernel.org" , Ian Campbell , Mark Rutland , Pawel Moll , Rob Herring Subject: Re: [PATCH 2/6] ARM: Tegra: Add CPU's OPPs for using cpufreq-cpu0 driver References: In-Reply-To: X-Enigmail-Version: 1.4.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2146 Lines: 57 On 08/07/2013 08:46 AM, Viresh Kumar wrote: > cpufreq-cpu0 driver needs OPPs to be present in DT which can be probed by it to > get frequency table. This patch adds OPPs and clock-latency to tegra cpu0 node > for multiple SoCs. > > Voltage levels aren't used until now for tegra and so a flat value which would > eventually be ignored is used to represent voltage. This patch is problematic w.r.t. DT being an ABI. We can certainly add new optional properties to a DT binding that enable new features. However, a new version of a binding can't require new properties to exist that didn't before, since that means that old DTs won't work with new kernels that require the new properties. As such, I believe we do need some Tegra-specific piece of code that defines these OPP tables in the kernel, so that the operating-points property is not needed. Similarly, we can't put invalid voltages into the DT, since if a later kernel version starts actually using that field, the HW will no longer work correctly. Unless perhaps we put 0 into the DT and make the binding define that 0 means "you can't change the voltage at all away from the boot value"? Is the operating-points property documented in Documentation/devicetree/bindings/ somewhere? (Also Cc'ing the DT mailing list and maintainers) > diff --git a/arch/arm/boot/dts/tegra114.dtsi b/arch/arm/boot/dts/tegra114.dtsi > index abf6c40..730e0d9 100644 > --- a/arch/arm/boot/dts/tegra114.dtsi > +++ b/arch/arm/boot/dts/tegra114.dtsi > @@ -438,6 +438,18 @@ > device_type = "cpu"; > compatible = "arm,cortex-a15"; > reg = <0>; > + operating-points = < > + /* kHz ignored */ > + 216000 1000000 > + 312000 1000000 > + 456000 1000000 > + 608000 1000000 > + 760000 1000000 > + 816000 1000000 > + 912000 1000000 > + 1000000 1000000 > + >; > + clock-latency = <300000>; > }; -- 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/