From mboxrd@z Thu Jan  1 00:00:00 1970
From: Pavel Machek <pavel@ucw.cz>
Subject: Re: [PATCH v9 2/4] amba: Don't unprepare the clocks if device driver
 wants IRQ safe runtime PM
Date: Tue, 4 Nov 2014 21:18:34 +0100
Message-ID: <20141104201834.GC15071@amd>
References: <1415105570-7871-1-git-send-email-k.kozlowski@samsung.com>
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To: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>, Len Brown <len.brown@intel.com>, Jonathan Corbet <corbet@lwn.net>, Russell King <linux@arm.linux.org.uk>, Dan Williams <dan.j.williams@intel.com>, Vinod Koul <vinod.koul@intel.com>, Ulf Hansson <ulf.hansson@linaro.org>, Alan Stern <stern@rowland.harvard.edu>, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org, Lars-Peter Clausen <lars@metafoo.de>, Michal Simek <michal.simek@xilinx.com>, Kevin Hilman <khilman@kernel.org>, Laurent Pinchart <laurent.pinchart@ideasonboard.com>, Kyungmin Park <kyungmin.park@samsung.com>, Marek Szyprowski <m.szyprowski@samsung.com>, Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

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?
									Pavel
-- 
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