Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758906Ab1ENUai (ORCPT ); Sat, 14 May 2011 16:30:38 -0400 Received: from mail-qy0-f174.google.com ([209.85.216.174]:44607 "EHLO mail-qy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754152Ab1ENUad convert rfc822-to-8bit (ORCPT ); Sat, 14 May 2011 16:30:33 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=w2HyX7pt6tgbVzfeKoA1ZLAgFYRccjcrhmS9297Ug7AUQVYuVsKXYZllfv29wQC3Na FhJiGeAlDfLIu2IDnGfaJCP6BSrM+483jaJW6Y/B5SeFqSuLZCfYBwlZj3ceJMrhPTOC x1OCK1vsglUMwnzZZZNM0RrRyRM/dENv6B8M4= MIME-Version: 1.0 In-Reply-To: <20110514162423.GA8292@gvim.org> References: <1305220265-9020-1-git-send-email-lamiaposta71@gmail.com> <20110514162423.GA8292@gvim.org> Date: Sat, 14 May 2011 22:30:31 +0200 Message-ID: Subject: Re: [linux-pm] pm loss development From: Raffaele Recalcati To: markgross@thegnar.org Cc: linux-pm@lists.linux-foundation.org, davinci-linux-open-source@linux.davincidsp.com, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7219 Lines: 183 On Sat, May 14, 2011 at 6:24 PM, mark gross wrote: > On Thu, May 12, 2011 at 07:11:01PM +0200, Raffaele Recalcati wrote: >> What happen normally in runtime pm implementation is that every devices >> are switched off and are enabled only when needed. >> In our case instead we have a completely functional embedded system and, >> when an asyncrhonous event appear, we have only some tens milliseconds >> before the actual power failure takes place. > > Very interesting!  I've been worried about a similar failure on battery > driven devices that can experience significant voltage droops when > battery gets old, or low, and we turn on the flashlight led, vibrator > and make the screen bright while a high volume ring tone gets played. > > I think 10ms is a bit unrealistic.  I think its more like 300uSec before > you hit brown out. In our circuit it is the real timing, but I can understand your situation. Are you sure about 300usec? >> This patchset add a support in order to switch off not vital part of the system, >> in order to allow the board to survive longer. >> This allow the possibility to save important data. >> >> The implementation has been written by Davide Ciminaghi. >> My work instead was about analyzing different previuos implementation, >> a first completely custom one, a second using runtime pm, arriving >> finally to that one. >> >> I have tested PM loss in our DaVinci dm365 basi board and I write here below a >> piece of code showing a possible usage. >> >> ------------------- >> >> static int powerfail_status; >> >> static irqreturn_t basi_powerfail_stop(int irq, void *dev_id); >> >> static irqreturn_t basi_powerfail_quick_check_start(int irq, void *dev_id) >> { >>         basi_mask_irq_gpio0(IRQ_DM365_GPIO0_2); >>         basi_unmask_irq_gpio0(IRQ_DM365_GPIO0_0); >> >>         /* PowerFail situation - START: power is going away */ >>         return IRQ_WAKE_THREAD; >> } >> >> static irqreturn_t basi_powerfail_start(int irq, void *dev_id) >> { >>         if (powerfail_status) >>                 return IRQ_HANDLED; >>         powerfail_status = 1; >>         pm_loss_power_changed(SYS_PWR_FAILING); >>         return IRQ_HANDLED; >> } >> >> >> static irqreturn_t basi_powerfail_quick_check_stop(int irq, void *dev_id) >> { >>         basi_mask_irq_gpio0(IRQ_DM365_GPIO0_0); >>         basi_unmask_irq_gpio0(IRQ_DM365_GPIO0_2); >> >>         /* PowerFail situation - STOP: power is coming back */ >>         return IRQ_WAKE_THREAD; >> } >> >> static irqreturn_t basi_powerfail_stop(int irq, void *dev_id) >> { >>         if (!powerfail_status) >>                 return IRQ_HANDLED; >>         powerfail_status = 0; >>         pm_loss_power_changed(SYS_PWR_GOOD); >>         return IRQ_HANDLED; >> } >> >> enum basi_pwrfail_prio { >>         BASI_PWR_FAIL_PRIO_0, >>         BASI_PWR_FAIL_MIN_PRIO = BASI_PWR_FAIL_PRIO_0, >>         BASI_PWR_FAIL_PRIO_1, >>         BASI_PWR_FAIL_PRIO_2, >>         BASI_PWR_FAIL_PRIO_3, >>         BASI_PWR_FAIL_MAX_PRIO = BASI_PWR_FAIL_PRIO_3, >> }; >> >> struct pm_loss_default_policy_item basi_pm_loss_policy_items[] = { >>         { >>                 .bus_name = "mmc", >>                 .bus_priority = BASI_PWR_FAIL_PRIO_1, >>         }, >>         { >>                 .bus_name = "platform", >>                 .bus_priority = BASI_PWR_FAIL_PRIO_2, >>         }, >> }; >> >> #define BASI_POLICY_NAME "basi-default" >> >> struct pm_loss_default_policy_table basi_pm_loss_policy_table = { >>         .name = BASI_POLICY_NAME, >>         .items = basi_pm_loss_policy_items, >>         .nitems = ARRAY_SIZE(basi_pm_loss_policy_items), >> }; >> >> static void basi_powerfail_configure(void) >> { >>         int stat; >>         struct pm_loss_policy *p; >>         stat = request_threaded_irq(IRQ_DM365_GPIO0_2, > Is this some comparator device that tugs on this gpio when the voltage > drops or goes to 0?  Is threaded irq fast enough? yes, there is a comparator. I need more data about timing, I'll try to add this info in some days. > Could we consider something that includes a hot path ISR based > notification call back to do stuff like blink off devices that don't > need to save state;  backlights, vibrators, flashlight LEDs, audio > output drivers <-- I'm not sure about audio HW, and then a slower path > for other things that can be put into lower power states? > > the all-clear notification that power is good again should be on a > slower path I would assume. First I get data, afterwards we can see if your need can be seen as an extension or something else. > > --mark > >>                                     basi_powerfail_quick_check_start, >>                                     basi_powerfail_start, >>                                     0, >>                                     "pwrfail-on", NULL); >>         if (stat < 0) >>                 printk(KERN_ERR "request_threaded_irq for IRQ%d (pwrfail-on) " >>                        "failed\n", IRQ_DM365_GPIO0_2); >>         stat = request_threaded_irq(IRQ_DM365_GPIO0_0, >>                                     basi_powerfail_quick_check_stop, >>                                     basi_powerfail_stop, 0, >>                                     "pwrfail-off", NULL); >>         if (stat < 0) >>                 printk(KERN_ERR "request_threaded_irq for IRQ%d (pwrfail-off) " >>                        "failed\n", IRQ_DM365_GPIO0_0); >>         basi_mask_irq_gpio0(IRQ_DM365_GPIO0_0); >>         p = pm_loss_setup_default_policy(&basi_pm_loss_policy_table); >> >>         if (!p) >>                 printk(KERN_ERR "Could not register pwr change policy\n"); >> >>         if (pm_loss_set_policy(BASI_POLICY_NAME) < 0) >>                 printk(KERN_ERR "Could not set %s power loss policy\n", >>                        BASI_POLICY_NAME); >> } >> >> int platform_pm_loss_power_changed(struct device *dev, >>                                    enum sys_power_state s) >> { >>         int ret = 0; >> >>         /* Calling platform bus pm_loss functions */ >>         pr_debug_pm_loss("platform_pm_loss_power_changed(%d)\n", s); >> >>         if (dev->driver && dev->driver->pm && >>                 dev->driver->pm->power_changed) >>                 ret = dev->driver->pm->power_changed(dev, s); >>         return ret; >> } >> >> >> >> >> _______________________________________________ >> linux-pm mailing list >> linux-pm@lists.linux-foundation.org >> https://lists.linux-foundation.org/mailman/listinfo/linux-pm > Bye, Raffaele -- 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/