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

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Message-ID: <CAFp+6iFcZwu3=2u5ig_F14UKxTXwb2Czrv3JjCqR6QGLPHzFqg@mail.gmail.com>
Date:	Mon, 28 Jan 2013 19:06:56 +0530
From:	Vivek Gautam <gautamvivek1987@...il.com>
To:	balbi@...com
Cc:	Vivek Gautam <gautam.vivek@...sung.com>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-samsung-soc@...r.kernel.org, gregkh@...uxfoundation.org,
	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

Hi Felipe,


On Mon, Jan 28, 2013 at 5:15 PM, Felipe Balbi <balbi@...com> wrote:
> 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.

I am fine with dropping pm_runtime_set_active(), actually thought
to put device in active state so that as and when system finds it idle,
force into suspend state.

I fact should i drop  pm_runtime_set_active() calls from other places too
(xhci-plat, dwc3-exynos, and samsung-usb3 phy) and call get_sync() alongwith
enable() ?

> 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...
>



-- 
Thanks & Regards
Vivek
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