From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kevin Hilman Subject: Re: [PATCH 4/4] PM / Runtime: Defer resuming of the device in pm_runtime_force_resume() Date: Thu, 30 Jun 2016 15:40:15 -0700 Message-ID: References: <1463485296-22742-1-git-send-email-ulf.hansson@linaro.org> <1463485296-22742-5-git-send-email-ulf.hansson@linaro.org> Mime-Version: 1.0 Content-Type: text/plain Return-path: Received: from mail-pf0-f170.google.com ([209.85.192.170]:35031 "EHLO mail-pf0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752539AbcF3WkU (ORCPT ); Thu, 30 Jun 2016 18:40:20 -0400 Received: by mail-pf0-f170.google.com with SMTP id c2so33646885pfa.2 for ; Thu, 30 Jun 2016 15:40:19 -0700 (PDT) In-Reply-To: (Geert Uytterhoeven's message of "Tue, 28 Jun 2016 18:26:36 +0200") Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Geert Uytterhoeven Cc: Ulf Hansson , "Rafael J. Wysocki" , Linux PM list , Len Brown , Pavel Machek , Geert Uytterhoeven , Lina Iyer , Axel Haslam , Marek Szyprowski , Jon Hunter , Andy Gross , Laurent Pinchart , Linux-Renesas Hi Geert, Geert Uytterhoeven writes: > Hi Ulf, Rafael, > > On Tue, May 17, 2016 at 1:41 PM, Ulf Hansson wrote: >> When the pm_runtime_force_suspend|resume() helpers were invented, we still >> had CONFIG_PM_RUNTIME and CONFIG_PM_SLEEP as separate Kconfig options. >> >> To make sure these helpers worked for all combinations and without >> introducing too much of complexity, the device was always resumed in >> pm_runtime_force_resume(). >> >> More precisely, when CONFIG_PM_SLEEP was set and CONFIG_PM_RUNTIME was >> unset, we needed to resume the device as the subsystem/driver couldn't >> rely on using runtime PM to do it. >> >> As the CONFIG_PM_RUNTIME option was merged into CONFIG_PM a while ago, it >> removed this combination, of using CONFIG_PM_SLEEP without the earlier >> CONFIG_PM_RUNTIME. >> >> For this reason we can now rely on the subsystem/driver to use runtime PM >> to resume the device, instead of forcing that to be done in all cases. In >> other words, let's defer this to a later point when it's actually needed. >> >> Signed-off-by: Ulf Hansson >> --- >> drivers/base/power/runtime.c | 11 +++++++++++ >> 1 file changed, 11 insertions(+) >> >> diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c >> index 09e4eb1..1db7b46 100644 >> --- a/drivers/base/power/runtime.c >> +++ b/drivers/base/power/runtime.c >> @@ -1509,6 +1509,17 @@ int pm_runtime_force_resume(struct device *dev) >> if (!pm_runtime_status_suspended(dev)) >> goto out; >> >> + /* >> + * The PM core increases the runtime PM usage count in the system PM >> + * prepare phase. If the count is greather than 1 at this point, someone >> + * else has also increased it. In that case, invoke the runtime resume >> + * callback for the device as that is likely what is expected. In other >> + * case we trust the subsystem/driver to runtime resume the device when >> + * it's actually needed. >> + */ >> + if (atomic_read(&dev->power.usage_count) < 2) >> + goto out; >> + >> ret = pm_runtime_set_active(dev); >> if (ret) >> goto out; > > This patch (commit eb13a0a1b6d5d5c2 in pm/linux-next) breaks resume on > sh73a0/kzm9g and r8a73a4/ape6evm. On these boards, the Ethernet controller is a > child of a local bus (bsc), whose clock (zb) is controlled through pm_clk and > simple-pm-bus, cfr. > > arch/arm/boot/dts/r8a73a4-ape6evm.dts > arch/arm/boot/dts/r8a73a4.dtsi > arch/arm/boot/dts/sh73a0-kzm9g.dts > arch/arm/boot/dts/sh73a0.dtsi > > During resume, the bus clock is not enabled, causing an imprecise abort > when accessing the Ethernet controller's registers. I have a hunch (without too much digging) that this may be an odd interaction with the direct_complete stuff since the simple-pm-bus has no callbacks. For kicks, could you add something like the hack below (untested) which will avoid the direct_complete path, and at least help indicate if that path is worth investigating further. Thanks, Kevin diff --git a/drivers/bus/simple-pm-bus.c b/drivers/bus/simple-pm-bus.c index c5eb46cbf388..63b95fb21510 100644 --- a/drivers/bus/simple-pm-bus.c +++ b/drivers/bus/simple-pm-bus.c @@ -36,6 +36,15 @@ static int simple_pm_bus_remove(struct platform_device *pdev) return 0; } +static int simple_pm_bus_prepare(struct device *dev) +{ + return pm_generic_prepare(dev); +} + +static const struct dev_pm_ops simple_pm_bus_ops = { + .prepare = simple_pm_bus_prepare, +}; + static const struct of_device_id simple_pm_bus_of_match[] = { { .compatible = "simple-pm-bus", }, { /* sentinel */ } @@ -48,6 +57,7 @@ static struct platform_driver simple_pm_bus_driver = { .driver = { .name = "simple-pm-bus", .of_match_table = simple_pm_bus_of_match, + .pm = &simple_pm_bus_ops, }, };