From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758608Ab2CSJF1 (ORCPT ); Mon, 19 Mar 2012 05:05:27 -0400 Received: from smtp-out-236.synserver.de ([212.40.185.236]:1095 "EHLO smtp-out-236.synserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754326Ab2CSJF0 (ORCPT ); Mon, 19 Mar 2012 05:05:26 -0400 X-SynServer-TrustedSrc: 1 X-SynServer-AuthUser: lars@metafoo.de X-SynServer-PPID: 9856 Message-ID: <4F66F75E.6040906@metafoo.de> Date: Mon, 19 Mar 2012 10:07:42 +0100 From: Lars-Peter Clausen User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.24) Gecko/20111114 Iceowl/1.0b2 Icedove/3.1.16 MIME-Version: 1.0 To: axel.lin@gmail.com CC: linux-kernel@vger.kernel.org, Liam Girdwood , Mark Brown Subject: Re: [PATCH v2 1/2] regulator: pcf50633: Don't write to reserved bits of AUTO output voltage select register References: <1331942824.6622.1.camel@phoenix> <4F65C1AA.40102@metafoo.de> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/19/2012 03:53 AM, Axel Lin wrote: > 2012/3/18 Lars-Peter Clausen : >> On 03/17/2012 01:07 AM, Axel Lin wrote: >>> The datasheet says 00000000 to 00101110 are reserved, and the min value of the >>> voltage setting is 1.8 V. >>> Thus don't write 0 to AUTO output voltage select register (address 1Ah). >>> >>> Table 50. AUTOOUT - AUTO output voltage select register (address 1Ah) bit description[1] >>> Bit Symbol Access Description >>> 7:0 auto_out R/W VO(prog) = 0.625 + auto_out × 0.025 V >>> eg. 00000000 to 00101110: reserved >>> 00101111: 1.8 V (min) >>> 01010011: 2.7 V >>> 01101010: 3.275 V >>> 01101011: 3.300 V >>> 01101100: 3.325 V >>> 01111111 : 3.800 V (max) >>> ..... ..... >>> 11111110 : 3.800 V >>> 11111111 : 3.800 V >>> >>> This patch also fixes a bug in pcf50633_regulator_list_voltage. >>> It is wrong to do "index += 0x2f" for PCF50633_REGULATOR_AUTO in >>> pcf50633_regulator_list_voltage. The purpose of adding 0x2f to index is because >>> current code return 0 in auto_voltage_bits when millivolts < 1800. >>> For millivolts > 1800, adding 0x2f to index is wrong. >>> >> >> I think you misunderstood what the current code does. The first usable voltage >> is 1.8V which is equal to a index of of 0x2f. So the driver adds 0x2f to the >> index so that there is not a headroom of 0x2f unusable voltages. So a selector >> of 0 translates to 1.8V, a selector of 1 translates to 1.825V and so on. > I think what I wry to explain is: > In regulator core _regulator_do_set_voltage function: > > if (rdev->desc->ops->set_voltage) { > ret = rdev->desc->ops->set_voltage(rdev, min_uV, max_uV, > &selector); > > if (rdev->desc->ops->list_voltage) > selector = rdev->desc->ops->list_voltage(rdev, > selector); > else > selector = -1; > > The list_voltage call here takes the selector got from set_voltage callback. > Thus adding 0x2f to the index in pcf50633_regulator_list_voltage looks > wrong to me. > Ah ok, now I understand what you mean. When the selector parameter to set_voltage was introduced we already had list_voltage adding the 0x2f, so from my point of view list_voltage is correct and the bug is in the commit which introduced the selector parameter to select voltage, that's why I was confused as to why you think there was a bug in list_voltage. But it all makes sense now, thanks. Luckily the bug is not so critical, since selector is not really used in _regulator_do_set_voltage in this case except for the trace message. - Lars