Re: [PATCH v5 3/4] amba: Don't unprepare the clocks if device driver wants IRQ safe runtime PM
From: Ulf Hansson <hidden>
Date: 2014-09-16 18:25:28
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On 16 September 2014 14:59, Krzysztof Kozlowski [off-list ref] wrote:
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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 <redacted> --- 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!?
+ + 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. I wonder if that could simplify both for the driver and for the amba bus? Russell, what do you think? Is it a bad idea?
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+ else + clk_disable_unprepare(pcdev->pclk); + } return ret; }@@ -106,7 +116,16 @@ static int amba_pm_runtime_resume(struct device *dev) int ret; if (dev->driver) { - ret = clk_prepare_enable(pcdev->pclk); + /* + * Drivers should not change pm_runtime_irq_safe() + * after probe. + */ + WARN_ON(pcdev->irq_safe != pm_runtime_is_irq_safe(dev)); + + if (pcdev->irq_safe) + ret = clk_enable(pcdev->pclk); + else + ret = clk_prepare_enable(pcdev->pclk); /* Failure is probably fatal to the system, but... */ if (ret) return ret;@@ -191,8 +210,10 @@ static int amba_probe(struct device *dev) pm_runtime_enable(dev); ret = pcdrv->probe(pcdev, id); - if (ret == 0) + if (ret == 0) { + pcdev->irq_safe = pm_runtime_is_irq_safe(dev);
I suggest to remove the local copy of this flag and to use pm_runtime_is_irq_safe(dev) directly instead.
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break; + } pm_runtime_disable(dev); pm_runtime_set_suspended(dev);diff --git a/include/linux/amba/bus.h b/include/linux/amba/bus.h index ad52027a9cbf..ce101e4497d6 100644 --- a/include/linux/amba/bus.h +++ b/include/linux/amba/bus.h@@ -32,6 +32,7 @@ struct amba_device { struct clk *pclk; unsigned int periphid; unsigned int irq[AMBA_NR_IRQS]; + unsigned int irq_safe:1; }; struct amba_driver { --1.9.1
Kind regards Uffe