From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752988AbbKXHuo (ORCPT ); Tue, 24 Nov 2015 02:50:44 -0500 Received: from mail-bn1bn0104.outbound.protection.outlook.com ([157.56.110.104]:22164 "EHLO na01-bn1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751470AbbKXHum (ORCPT ); Tue, 24 Nov 2015 02:50:42 -0500 X-Greylist: delayed 878 seconds by postgrey-1.27 at vger.kernel.org; Tue, 24 Nov 2015 02:50:41 EST Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=Ping.Bai@freescale.com; Subject: Re: [PATCH] cpufreq: imx: Add cpufreq driver for imx7D/Solo SOC To: Lucas Stach References: <1448287669-3600-1-git-send-email-b51503@freescale.com> <1448271626.3689.7.camel@pengutronix.de> CC: , , , From: Bai Ping Message-ID: <5654133A.6010506@freescale.com> Date: Tue, 24 Nov 2015 15:35:22 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <1448271626.3689.7.camel@pengutronix.de> Content-Type: text/plain; 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This patch adds the >> cpufreq driver for i.MX7Dual/Solo. >> > So, what are those requirements, which could not be matched with > cpufreq-dt? We should really try to not add another cpufreq driver. the requirement is the PLL1 used to source the CPU core clock can NOT change frequency on the fly, during the PLL1 frequency change, not clock output from this PLL1 in a short time. this will lead to glitch to the core clock. so before we change the PLL1's frequency, we must switch the CPU core clock to another clock source, after the PLL1 frequency has been changed, we switch back core clock to PLL1. > I don't see anything special in here. A single regulator and some clocks > needing to be controlled in the right way. That's already handled for > i.MX5 with cpufreq-dt. Please look up how it is done there and try to do > it the same way for MX7, or provide substantial information why it > couldn't be done. I have checked the i.MX5 cpufreq, As on i.MX5, no need to take care of the PLL's frequency change flow, so the cpufreq-dt is the best one to support cpufreq. But on i.MX7, the PLL design is not the same as on i.MX5, additional steps needed in CPU frequency changing flow. the issue that can NOT be tackled by cpufreq-dt is additional step used by PLL frequency change. BR Jacky Bai > > Regards, > Lucas