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Date: Tue, 16 Sep 2014 20:52:55 +0100 From: Russell King - ARM Linux <linux@....linux.org.uk> To: Ulf Hansson <ulf.hansson@...aro.org> Cc: Krzysztof Kozlowski <k.kozlowski@...sung.com>, Dan Williams <dan.j.williams@...el.com>, Vinod Koul <vinod.koul@...el.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, dmaengine@...r.kernel.org, Grant Likely <grant.likely@...aro.org>, Lars-Peter Clausen <lars@...afoo.de>, Michal Simek <michal.simek@...inx.com>, "Rafael J. Wysocki" <rjw@...ysocki.net>, Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>, Randy Dunlap <rdunlap@...radead.org>, Alan Stern <stern@...land.harvard.edu>, "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>, "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>, Kyungmin Park <kyungmin.park@...sung.com>, Marek Szyprowski <m.szyprowski@...sung.com>, Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com> Subject: Re: [PATCH v5 3/4] amba: Don't unprepare the clocks if device driver wants IRQ safe runtime PM On Tue, Sep 16, 2014 at 08:25:25PM +0200, Ulf Hansson wrote: > On 16 September 2014 14:59, Krzysztof Kozlowski <k.kozlowski@...sung.com> 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. > > > > Detect the device driver behavior after calling its probe function and > > store it. During runtime suspend/resume deal with clocks according to > > stored value. > > > > Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com> > > --- > > drivers/amba/bus.c | 29 +++++++++++++++++++++++++---- > > include/linux/amba/bus.h | 1 + > > 2 files changed, 26 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c > > index 3cf61a127ee5..e8fd5706954f 100644 > > --- a/drivers/amba/bus.c > > +++ b/drivers/amba/bus.c > > @@ -94,8 +94,18 @@ 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) { > > + /* > > + * Drivers should not change pm_runtime_irq_safe() > > + * after probe. > > + */ > > + WARN_ON(pcdev->irq_safe != pm_runtime_is_irq_safe(dev)); > > Do we really need a WARN_ON here. Driver shouldn't update their > irq_safe value dynamically, right!? The driver shouldn't update it dynamically, and this makes sure *that* is enforced since we end up depending on that property. Hence the check is sensible (and I even suggested it.) > > + > > + if (pcdev->irq_safe) > > + clk_disable(pcdev->pclk); > > Since the irq_safe flag, could be considered as a special case, an > option for these cases - could be to leave the clock to be entirely > handled from the driver's runtime PM callback instead. Too many sub-clauses to make much sense of that statement. I don't want drivers messing around with this stuff. This is the /bus/ clock, not a device specific clock. -- FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net. -- 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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