linux-kernel - Re: [PATCH 2/2] usb: dwc3: of_simple: don't call pm_runtime_set

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Message-ID: <87bmcwcl1j.fsf@linux.intel.com>
Date:   Thu, 31 May 2018 10:59:52 +0300
From:   Felipe Balbi <balbi@...nel.org>
To:     Roger Quadros <rogerq@...com>, Tero Kristo <t-kristo@...com>,
        "Gerlach\, Dave" <d-gerlach@...com>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Nishanth Menon <nm@...com>, "Nori\, Sekhar" <nsekhar@...com>
Subject: Re: [PATCH 2/2] usb: dwc3: of_simple: don't call pm_runtime_set_active()


Hi,

Roger Quadros <rogerq@...com> writes:

> On 30/05/18 15:31, Felipe Balbi wrote:
>> Roger Quadros <rogerq@...com> writes:
>> 
>>> Don't call pm_runtime_set_active() as it will prevent the device
>>> from being activated in the next pm_runtime_get_sync() call.
>>>
>>> Also call pm_runtime_get_sync() before of_platform_populate().
>>>
>>> Signed-off-by: Roger Quadros <rogerq@...com>
>> 
>> This patch is wrong.
>> 
>>> ---
>>>  drivers/usb/dwc3/dwc3-of-simple.c | 7 +++----
>>>  1 file changed, 3 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/usb/dwc3/dwc3-of-simple.c b/drivers/usb/dwc3/dwc3-of-simple.c
>>> index e98d221..2cbb5c0 100644
>>> --- a/drivers/usb/dwc3/dwc3-of-simple.c
>>> +++ b/drivers/usb/dwc3/dwc3-of-simple.c
>>> @@ -121,6 +121,9 @@ static int dwc3_of_simple_probe(struct platform_device *pdev)
>>>  	if (ret)
>>>  		goto err_resetc_assert;
>>>  
>>> +	pm_runtime_enable(dev);
>>> +	pm_runtime_get_sync(dev);
>> 
>> No, this is the wrong way to do things. My device should be enabled
>> already from probe, specially since I have already enabled clocks.
>
> As far as I understood just enabling clocks (which might not include bus clock)
> doesn't ensure device is enabled.
>
> Did you mean that I don't need to do a pm_runtime_get_sync() to enable my device in probe?
> Who is enabling by device for me then? Is device core supposed to do it?

Not device core, but the bus code. Look at how PCI handles it. IIRC,
only TI's omap_device behaves peculiarly WRT probe & pm runtime.

> The issue I was facing is that without this patch my device wasn't being enabled
> as pm_runtime_set_active() is being done _before_ pm_runtime_get_sync().
> It could be an issue with the platform's PM domain code as well.

Could be

-- 
balbi

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