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Message-id: <1410764863.4690.3.camel@AMDC1943>
Subject: Re: [RFC PATCH v2 1/2] amba: Allow AMBA drivers to use their own
 runtime PM
From: Krzysztof Kozlowski <k.kozlowski@samsung.com>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Dan Williams <dan.j.williams@intel.com>, Vinod Koul <vinod.koul@intel.com>,
        linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Grant Likely <grant.likely@linaro.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Michal Simek <michal.simek@xilinx.com>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Date: Mon, 15 Sep 2014 09:07:43 +0200
In-reply-to: <20140912151352.GK12361@n2100.arm.linux.org.uk>
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On pią, 2014-09-12 at 16:13 +0100, Russell King - ARM Linux wrote:
> On Fri, Sep 12, 2014 at 04:56:18PM +0200, 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()). If such driver
> > implements its own runtime PM functions then assume it will handle the
> > runtime PM completely and it will replace our clock handling.
> > 
> > Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> 
> Actually, I'd rather just revert 5303c0f46c8708fff4148ebcc491f78710356952
> which is clearly the wrong thing to do when we have non-IRQ safe runtime
> PM.
> 
> What we /could/ do instead is to check whether irq_safe is set after
> probe, record that, and then select whether to use the prepare/unprepare
> methods based on that.  (Drivers should never dynamically change this.)

I'll try this approach.

Thank you for feedback,
Krzysztof