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Date: Wed, 05 Nov 2014 09:42:58 +0100 From: Krzysztof Kozlowski <k.kozlowski@...sung.com> To: Pavel Machek <pavel@....cz> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>, Len Brown <len.brown@...el.com>, Jonathan Corbet <corbet@....net>, Russell King <linux@....linux.org.uk>, Dan Williams <dan.j.williams@...el.com>, Vinod Koul <vinod.koul@...el.com>, Ulf Hansson <ulf.hansson@...aro.org>, Alan Stern <stern@...land.harvard.edu>, linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, dmaengine@...r.kernel.org, Lars-Peter Clausen <lars@...afoo.de>, Michal Simek <michal.simek@...inx.com>, Kevin Hilman <khilman@...nel.org>, Laurent Pinchart <laurent.pinchart@...asonboard.com>, Kyungmin Park <kyungmin.park@...sung.com>, Marek Szyprowski <m.szyprowski@...sung.com>, Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com> Subject: Re: [PATCH v9 2/4] amba: Don't unprepare the clocks if device driver wants IRQ safe runtime PM On wto, 2014-11-04 at 21:18 +0100, Pavel Machek wrote: > On Tue 2014-11-04 13:52:48, Krzysztof Kozlowski wrote: > > The AMBA bus driver defines runtime Power Management functions which > > disable and unprepare AMBA bus clock. This is problematic for runtime PM > > because unpreparing a clock might sleep so it is not interrupt safe. > > > > However some drivers may want to implement runtime PM functions in > > interrupt-safe way (see pm_runtime_irq_safe()). In such case the AMBA > > bus driver should only disable/enable the clock in runtime suspend and > > resume callbacks. > > > > > /* > > * Hooks to provide runtime PM of the pclk (bus clock). It is safe to > > * enable/disable the bus clock at runtime PM suspend/resume as this > > @@ -95,8 +102,14 @@ static int amba_pm_runtime_suspend(struct device *dev) > > struct amba_device *pcdev = to_amba_device(dev); > > int ret = pm_generic_runtime_suspend(dev); > > > > - if (ret == 0 && dev->driver) > > - clk_disable_unprepare(pcdev->pclk); > > + if (ret == 0 && dev->driver) { > > + pcdev->irq_safe = get_pm_runtime_irq_safe(dev); > > + > > + if (pcdev->irq_safe) > > + clk_disable(pcdev->pclk); > > + else > > + clk_disable_unprepare(pcdev->pclk); > > + } > > So you can handle the case of !pcdev->irq_safe. What is the penalty > for always assuming !pcdev->irq_safe? The penalty (for pl330 driver) would be that the runtime resume/suspend cannot happen from atomic context => pm_runtime_get_sync() cannot be called from atomic context => complete rework of runtime PM for pl330 DMA driver because now one of pm_runtime_get_sync() calls is in device_issue_pending callback which may not sleep. And by "rework" I also mean that I do not know how to do this... yet. Best regards, Krzysztof -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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