linux-kernel - Re: [PATCH 2/4] USB: dwc3: Adjust runtime pm the dwc3 driver to allow runtime suspend

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Message-ID: <20130128114554.GE28698@arwen.pp.htv.fi>
Date:	Mon, 28 Jan 2013 13:45:54 +0200
From:	Felipe Balbi <balbi@...com>
To:	Vivek Gautam <gautam.vivek@...sung.com>
CC:	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-omap@...r.kernel.org>, <linux-samsung-soc@...r.kernel.org>,
	<gregkh@...uxfoundation.org>, <balbi@...com>,
	<sarah.a.sharp@...ux.intel.com>, <kgene.kim@...sung.com>,
	<dianders@...omium.org>, <sylvester.nawrocki@...il.com>,
	<tomasz.figa@...il.com>
Subject: Re: [PATCH 2/4] USB: dwc3: Adjust runtime pm the dwc3 driver to
 allow runtime suspend

On Mon, Jan 28, 2013 at 05:12:26PM +0530, Vivek Gautam wrote:
> The current code in the dwc3 probe effectively disables runtime pm
> from ever working because it calls a get() that was never put() until
> device removal.  Change the runtime pm code to match the standard
> formula and allow runtime pm to function.
> 
> Note that this doesn't enable full runtime pm on the DWC3 device in
> that the port isn't put into a lower power mode when not used.
> However it does allow users of dwc3 (like dwc3-exynos) to do some
> amount of runtime power management.
> 
> Signed-off-by: Vivek Gautam <gautam.vivek@...sung.com>
> Signed-off-by: Doug Anderson <dianders@...omium.org>
> ---
>  drivers/usb/dwc3/core.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 3a4004a..59c2494 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -453,6 +453,7 @@ static int dwc3_probe(struct platform_device *pdev)
>  	if (of_get_property(node, "tx-fifo-resize", NULL))
>  		dwc->needs_fifo_resize = true;
>  
> +	pm_runtime_set_active(dev);

this usage of pm_runtime_set_active() actually makes me a bit scared. At
least OMAP starts with the device switched off, so this will probably
break OMAP at least. OTOH, calling ->runtime_resume() during probe()
might not make that much sense after all, but the way OMAP is
implemented, we won't get clocks turned on if this ->runtime_resume()
method isn't called.

/me starts to wonder whether OMAP implementation is flakey and what
should be done here...

-- 
balbi

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