linux-kernel - Re: [PATCH V7 2/3] dma: add Qualcomm Technologies HIDMA management driver

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Message-ID: <20151205075826.GI1854@localhost>
Date:	Sat, 5 Dec 2015 13:28:26 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Sinan Kaya <okaya@...eaurora.org>
Cc:	dmaengine@...r.kernel.org, timur@...eaurora.org,
	cov@...eaurora.org, jcm@...hat.com, agross@...eaurora.org,
	arnd@...db.de, linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V7 2/3] dma: add Qualcomm Technologies HIDMA management
 driver

On Tue, Dec 01, 2015 at 11:57:34PM -0500, Sinan Kaya wrote:
> On 11/30/2015 10:17 PM, Vinod Koul wrote:
> > On Mon, Nov 30, 2015 at 09:42:01AM -0500, Sinan Kaya wrote:
> > 
> >>>> +static int hidma_mgmt_probe(struct platform_device *pdev)
> >>>> +{
> >>>> +	struct hidma_mgmt_dev *mgmtdev;
> >>>> +	struct resource *res;
> >>>> +	void __iomem *virtaddr;
> >>>> +	int irq;
> >>>> +	int rc;
> >>>> +	u32 val;
> >>>> +
> >>>> +	pm_runtime_set_autosuspend_delay(&pdev->dev, AUTOSUSPEND_TIMEOUT);
> >>>> +	pm_runtime_use_autosuspend(&pdev->dev);
> >>>> +	pm_runtime_set_active(&pdev->dev);
> >>>> +	pm_runtime_enable(&pdev->dev);
> >>>
> >>> at this time pm core will treat device as fully enabled and pm methods can
> >>> be invoked, but you are not ready yet right. Typically these are done at the
> >>> end of the probe unless you have a reason... 
> >>
> >> I need it here because the clocks are declared as ACPI power resources.
> >> The kernel is turning off all power resources during initialization. In
> >> order for this code to touch the hardware, I need to call enable so that
> >> clocks are enabled once again.
> > 
> > The question is are you ready in your driver routines to be invoked by pm
> > core?
> > 
> 
> I don't have any support for suspend and resume PM APIs. The only PM
> interface I support is PM runtime. PM can turn on/off the clocks based
> on the reference counts it maintains after get/set APIs. Since PM is
> turning off the clocks during power up before my driver load, I do need
> to grab this lock to re-enable it during HW initialization. Then, let PM
> turn off the clocks again after the AUTOSUSPEND_TIMEOUT when I'm done.
> 
> Is there any other interaction with the PM that I'm not aware of?

No this is fine. The the runtime_resume will be onvoked and it will request
resources are those set before you enable the device?

-- 
~Vinod
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