Messages in this thread | | | Subject | Re: [PATCH v9 2/4] amba: Don't unprepare the clocks if device driver wants IRQ safe runtime PM | From | Krzysztof Kozlowski <> | Date | Wed, 05 Nov 2014 09:42:58 +0100 |
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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
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