Messages in this thread | | | Date | Thu, 13 Nov 2014 10:03:08 +0100 | Subject | Re: [PATCH v11 5/6] dmaengine: pl330: Add PM sleep support | From | Ulf Hansson <> |
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On 13 November 2014 02:37, Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > On Wednesday, November 12, 2014 03:32:27 PM Krzysztof Kozlowski wrote: >> Add system suspend/resume capabilities to the pl330 driver so the amba >> bus clock could be also unprepared to conserve energy. >> >> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com> >> --- >> drivers/dma/pl330.c | 37 +++++++++++++++++++++++++++++++++++++ >> 1 file changed, 37 insertions(+) >> >> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c >> index c3bd3584f261..fd71777fc565 100644 >> --- a/drivers/dma/pl330.c >> +++ b/drivers/dma/pl330.c >> @@ -2627,6 +2627,42 @@ static int pl330_dma_device_slave_caps(struct dma_chan *dchan, >> return 0; >> } >> >> +/* >> + * Runtime PM callbacks are provided by amba/bus.c driver. >> + * >> + * It is assumed here that IRQ safe runtime PM is chosen in probe and amba >> + * bus driver will only disable/enable the clock in runtime PM callbacks. >> + */ >> +static int __maybe_unused pl330_suspend(struct device *dev) >> +{ >> + struct amba_device *pcdev = to_amba_device(dev); >> + >> + if (!pm_runtime_status_suspended(dev)) { > > It generally isn't safe to call that in .suspend(), because the status may still > change in theory. On the other hand, if you do that in .suspend_late(), you'll > be safe from that. >
Just to clarify that statement; it's safe in a ->suspend_late() callback, because runtime PM has been disabled by the PM core.
That's also the reason why the pm_runtime_force_suspend() helper is disabling runtime PM, such it may be used in some of the earlier phases of the system PM callbacks.
Kind regards Uffe
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