Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031082AbbEEIwl (ORCPT ); Tue, 5 May 2015 04:52:41 -0400 Received: from mail-oi0-f47.google.com ([209.85.218.47]:34463 "EHLO mail-oi0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031013AbbEEIwS (ORCPT ); Tue, 5 May 2015 04:52:18 -0400 MIME-Version: 1.0 In-Reply-To: <6ED8E3B22081A4459DAC7699F3695FB7014B219017@SW-EX-MBX02.diasemi.com> References: <639fd177d5ddd4ce80df45f9d774cc971b286ef9.1430393194.git.stwiss.opensource@diasemi.com> <6ED8E3B22081A4459DAC7699F3695FB7014B219017@SW-EX-MBX02.diasemi.com> Date: Tue, 5 May 2015 10:52:17 +0200 X-Google-Sender-Auth: rbjdwJTEP5DrtsZzAe_5dN9fCPA Message-ID: Subject: Re: [PATCH V3 3/3] mfd: da9063: MFD support for OnKey driver From: Geert Uytterhoeven To: "Opensource [Steve Twiss]" Cc: Lee Jones , Samuel Ortiz , DT , David Dajun Chen , Dmitry Torokhov , INPUT , Ian Campbell , Kumar Gala , LKML , Mark Rutland , Pawel Moll , Rob Herring , Support Opensource Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3085 Lines: 76 Hi Steve, On Tue, May 5, 2015 at 10:36 AM, Opensource [Steve Twiss] wrote: > On 04 May 2015 08:47, Geert Uytterhoeven wrote: >> On Thu, Apr 30, 2015 at 1:26 PM, S Twiss >> wrote: >> > Add MFD support for the DA9063 OnKey driver >> > +static int da9063_clear_fault_log(struct da9063 *da9063) >> > +{ >> > +} >> > + >> > int da9063_device_init(struct da9063 *da9063, unsigned int irq) >> > { >> > struct da9063_pdata *pdata = da9063->dev->platform_data; >> > int model, variant_id, variant_code; >> > int ret; >> > >> > + ret = da9063_clear_fault_log(da9063); >> > + if (ret < 0) >> > + dev_err(da9063->dev, "Cannot clear fault log\n"); >> > + >> > if (pdata) { >> > da9063->flags = pdata->flags; >> > da9063->irq_base = pdata->irq_base; >> >> The code above doesn't seem to match the patch description. >> Can you please explain why it is needed? > > Yes, at first it does seem that the fault-log clearing function is unrelated to the > "MFD support for the DA9063 OnKey driver", but there is an important connection > that makes it essential for the OnKey driver in this case. > > I have made some explanation of the OnKey's operation in this thread here: > https://lkml.org/lkml/2015/4/29/406 > > But I only described the OnKey's point-of-view for case (4) of the "OnKey operation" > Case (4): the long-long press and no key release -- the hardware power-cut when > software is unable to respond (for whatever reason). > > In this case, if the software was not responsive and a hardware shutdown of the > device was chosen, the FAULT_LOG would persist with information that would be > accessible when the device was restarted: it would be possible to take action the > next time the device was turned on again (maybe to trigger some mitigation exercise > in the bootloader -- e.g. say to complete memory checks or put the device into a > safe mode). > > However this mitigation exercise and clearance of the fault-log cannot be counted on > outside the Linux kernel and so the clearance function da9063_clear_fault_log () has > been done here. > > If this clearance function did not exist, then after a hardware shutdown (due to S/W > failure), the next time the device is restarted the FAULT_LOG would persist with values > from the previous error. Thanks for your explanation! Please add (some parts of it) to the patch description. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- 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/