Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

From: Kevin Hilman <khilman@deeprootsystems.com>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Sourav <sourav.poddar@ti.com>, Paul Walmsley <paul@pwsan.com>,
	Felipe Balbi <balbi@ti.com>,
	gregkh@linuxfoundation.org, tony@atomide.com,
	linux-kernel@vger.kernel.org, santosh.shilimkar@ti.com,
	linux-serial@vger.kernel.org, linux-omap@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, alan@linux.intel.com
Subject: Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.
Date: Fri, 12 Oct 2012 10:59:22 -0700	[thread overview]
Message-ID: <877gqv4lmt.fsf@deeprootsystems.com> (raw)
In-Reply-To: <20121012164202.GQ28061@n2100.arm.linux.org.uk> (Russell King's message of "Fri, 12 Oct 2012 17:42:02 +0100")

Russell King - ARM Linux <linux@arm.linux.org.uk> writes:

> On Fri, Oct 12, 2012 at 09:35:54AM -0700, Kevin Hilman wrote:
>> Sourav <sourav.poddar@ti.com> writes:
>> > diff --git a/drivers/tty/serial/omap-serial.c
>> > b/drivers/tty/serial/omap-serial.c
>> > index 6ede6fd..3fbc7f7 100644
>> > --- a/drivers/tty/serial/omap-serial.c
>> > +++ b/drivers/tty/serial/omap-serial.c
>> > @@ -1414,6 +1414,7 @@ static int __devinit serial_omap_probe(struct
>> > platform_device *pdev)
>> >         INIT_WORK(&up->qos_work, serial_omap_uart_qos_work);
>> >
>> >         platform_set_drvdata(pdev, up);
>> > +       pm_runtime_set_active(&pdev->dev);
>> 
>> NAK.
>> 
>> This will obviously break platforms where the UARTs are not active
>> before driver loads.
>
> I thought I had proposed a solution for this issue, which was this
> sequence:
>
>         omap_device_enable(dev);                                                
>         pm_runtime_set_active(dev);                                             
>         pm_runtime_enable(dev);                                                 
>
> Yes, I can understand people not liking the omap_device_enable()
> there, but I also notice that the email suggesting that never got a
> reply either - not even a "I tried this and it doesn't work" or "it
> does work".

Yes, that solution would work (though I didn't actually try it.)

However, we can't use omap_device_enable() in the driver.  We're trying
to clean all the drivers of OMAP-specific APIs.  That being said,
something similar could be done in the device/board init code to ensure
the UART HW is in the state that the driver is expecting it, but again,
that would just mask the real problem which is that a (re)init of the
console UART on 2420/n800 is causing output to disappear.

As I detailed in an earlier response, I still think it's the fact that
the pinmux is not setup correctly for the console UART pins in the board
file, so when the UART is initialized, its mux settings are changed from
the bootloader defaults, causing output to disappear.

> As such, it seems this issue isn't making any progress as we had
> already established that merely doing a "pm_runtime_set_active()"
> before "pm_runtime_enable()" was going to break other platforms.

Agreed.

Kevin