linux-kernel - Re: [PATCH v1 0/3] console, serial8250: Disable PM and DMA ops

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Message-ID: <CAHp75VfqAK6+dPWWkQXjy0V-AFSGLSDJ9CmnUv=ba0F66TDTVg@mail.gmail.com>
Date:   Thu, 17 May 2018 19:38:59 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v1 0/3] console, serial8250: Disable PM and DMA ops

On Thu, May 17, 2018 at 4:56 PM, Tony Lindgren <tony@...mide.com> wrote:
> * Andy Shevchenko <andriy.shevchenko@...ux.intel.com> [180516 13:12]:
>> On Wed, 2018-05-16 at 12:47 +0200, Sebastian Andrzej Siewior wrote:
>> > But since I am on it. You have to enable runtime-PM for the UART. So
>> > what is the problem if you simply don't enable it for the UART which
>> > used as the kernel console?
>>
>> How do I know at the ->probe() time that device in question is going to
>> be kernel console? Maybe I missed simple way of it.
>
> Hmm parse the kernel cmdline maybe? :)
>
> BTW, kernel already has earlycon doing exactly what you're trying to do.

I'm sorry, I didn't follow. What exactly earlycon does?

The problem is in 8250 driver. The issue with runtime PM used in atomic context.
So, I can, of course just remove callbacks from the console ->write().
Though it will prevent to use kernel console anyway.

-- 
With Best Regards,
Andy Shevchenko