Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030231Ab3DSMBs (ORCPT ); Fri, 19 Apr 2013 08:01:48 -0400 Received: from arroyo.ext.ti.com ([192.94.94.40]:50995 "EHLO arroyo.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S968123Ab3DSMBq (ORCPT ); Fri, 19 Apr 2013 08:01:46 -0400 From: Taras Kondratiuk To: , , , , CC: , , , Taras Kondratiuk Subject: [RFC PATCH 0/2] cpufreq/regulator: Limit minimum voltage only Date: Fri, 19 Apr 2013 14:55:52 +0300 Message-ID: <1366372554-20866-1-git-send-email-taras@ti.com> X-Mailer: git-send-email 1.7.9.5 MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1531 Lines: 36 Using a "voltage tolerance" for doing DVFS is not a proper way. It leads to a few issues: - voltage is limited to a narrow range near OPP voltage, so other consumers of the same regulator can't set their own constraints if they don't overlap with this narrow range. No ganged rails :( - usually OPP voltage is an absolute minimum voltage necessary for correct work (not taking into account AVS). Applying plus/minus tolerance can lead to an unstable device. For example omap-cpufreq has 4% tolerance configured, so for OMAP4430 MPU OPP50 we get 0.984V instead of 1.025V. This series adds a new API to regulator FW to limit only minimum voltage. As example API is used for cpufreq-cpu0, but if it is accepted I'll fix other drivers (omap-cpufreq, imx6q-cpufreq, etc). Maybe regulator_set_voltage_tol() should be removed completely, because it started to be used in a wrong way. Patches are based on v3.9-rc7. I've tested them on v3.8 based branch on OMAP4430 Blaze board. Taras Kondratiuk (2): regulator: core: Add regulator_set_voltage_min() cpufreq: cpufreq-cpu0: Limit minimum voltage only drivers/cpufreq/cpufreq-cpu0.c | 12 ++++-------- include/linux/regulator/consumer.h | 6 ++++++ 2 files changed, 10 insertions(+), 8 deletions(-) -- 1.7.9.5 -- 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/