From mboxrd@z Thu Jan 1 00:00:00 1970 From: Krzysztof Kozlowski Subject: Re: [PATCH 03/13] power: max17047_battery: The temp alert values are 8-bit 2's complement Date: Fri, 14 Apr 2017 17:26:01 +0200 Message-ID: <20170414152601.waxqjuu5z6tde7b4@kozik-lap> References: <20170414125919.25771-1-hdegoede@redhat.com> <20170414125919.25771-3-hdegoede@redhat.com> <20170414150927.eo5n2derv26dskcd@kozik-lap> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Return-path: Received: from mail-wm0-f67.google.com ([74.125.82.67]:34663 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751521AbdDNP0F (ORCPT ); Fri, 14 Apr 2017 11:26:05 -0400 Received: by mail-wm0-f67.google.com with SMTP id x75so18280896wma.1 for ; Fri, 14 Apr 2017 08:26:04 -0700 (PDT) Content-Disposition: inline In-Reply-To: Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Hans de Goede Cc: Sebastian Reichel , Bartlomiej Zolnierkiewicz , linux-pm@vger.kernel.org On Fri, Apr 14, 2017 at 05:16:32PM +0200, Hans de Goede wrote: > Hi, > > On 14-04-17 17:09, Krzysztof Kozlowski wrote: > > On Fri, Apr 14, 2017 at 02:59:09PM +0200, Hans de Goede wrote: > > > The temp alert values are 8-bit 2's complement, so sign-extend them > > > before reporting them back to the caller. > > > > Are you sure that these are reported with sign bit? I couldn't find > > confirmation of this in datasheet. > > From: MAX17047-MAX17050.pdf > > "T ALRT Threshold Register (02h) > The T ALRT Threshold register sets upper and lower limits > that generate an ALRT pin interrupt if exceeded by the > Temperature register value. The upper 8 bits set the maxi- > mum value and the lower 8 bits set the minimum value. > Interrupt threshold limits are stored in two’s-complement > format" That does not say it is signed. It might be still from 0 to 255. > And the reset default of 7F80h also hints at this, > as it is +127 for max -128 for min (aka temp based > alerts disabled). In this case looks correct... but max77693 fuel gauge datasheet says about TALRT_Th (0x02): Reset value: 0x00FF "...At power up, the thresholds default to their maximum settings- 7F80h (disabled)." which as you see contains to different reset values... Ehhh... Max17047max17050 datasheet looks a little bit more chaotic/organized so I guess it should be used as a source. Best regards, Krzysztof