From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Tony Lindgren <tony@atomide.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Petr Mladek <pmladek@suse.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jslaby@suse.com>,
"open list:SERIAL DRIVERS" <linux-serial@vger.kernel.org>,
Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH v1 0/3] console, serial8250: Disable PM and DMA ops
Date: Wed, 23 May 2018 00:39:46 +0300 [thread overview]
Message-ID: <CAHp75Ve56pyEC41XZ9i9yxBNberQe=ee2miQL0v9T4vRtkWPBQ@mail.gmail.com> (raw)
In-Reply-To: <20180517193008.GV25808@atomide.com>
On Thu, May 17, 2018 at 10:30 PM, Tony Lindgren <tony@atomide.com> wrote:
> * Andy Shevchenko <andy.shevchenko@gmail.com> [180517 16:41]:
>> On Thu, May 17, 2018 at 4:56 PM, Tony Lindgren <tony@atomide.com> wrote:
>> > * Andy Shevchenko <andriy.shevchenko@linux.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?
>
> It provides a console very early on, see earlycon in
> Documentation/admin-guide/kernel-parameters.txt
Yes, but what we are talking is to put the kernel console out of power
management due to _real_ issues with it.
>> The problem is in 8250 driver. The issue with runtime PM used in atomic context.
>
> So how about add some "noidle" kernel command line parameter for console
> that calls
> pm_runtime_forbid() and then you have the UART permanently
> on.
IIUC _forbid() can be overwritten via sysfs.
And I would prefer to do other way around, something like console.idle
and put default for OMAP to yes and no for everything else.
> Hmm I guess you could make also serial8250_rpm_get() do nothing
> based on that.
Have you seen entire series which I keep here:
https://bitbucket.org/andy-shev/linux/branch/topic/uart/rpm?
Among other things it gets rid of those specific callbacks entirely.
> I do agree the serial runtime PM has an issue if it depends on
> pm_runtime_irq_safe() being set.
It's more than an issue. The so called "support" of RPM for UART is
_based on the hack_.
I would love to NAK that in the first place if I would have known of it in time.
>> So, I can, of course just remove callbacks from the console ->write().
>> Though it will prevent to use kernel console anyway.
>
> Please et's not start breaking things, we already see a constant
> flow of regressions on weekly basis.
Now we are stick with a hack and the case based on that is against
fixing things.
This is how it looks from my side.
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2018-05-22 21:39 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-15 18:34 [PATCH v1 0/3] console, serial8250: Disable PM and DMA ops Andy Shevchenko
2018-05-15 18:34 ` [PATCH v1 1/3] console: introduce ->exit() callback Andy Shevchenko
2018-05-15 18:34 ` [PATCH v1 2/3] serial: 8250_port: Don't use power management for kernel console Andy Shevchenko
2018-05-15 18:34 ` [PATCH v1 3/3] serial: 8250_port: Disable DMA operations " Andy Shevchenko
2018-05-16 10:55 ` Sebastian Andrzej Siewior
2018-05-16 12:58 ` Andy Shevchenko
2018-05-16 18:20 ` Sebastian Andrzej Siewior
2018-05-15 18:37 ` [PATCH v1 0/3] console, serial8250: Disable PM and DMA ops Andy Shevchenko
2018-05-16 10:08 ` Sebastian Andrzej Siewior
2018-05-16 10:17 ` Andy Shevchenko
2018-05-16 10:47 ` Sebastian Andrzej Siewior
2018-05-16 13:10 ` Andy Shevchenko
2018-05-17 13:56 ` Tony Lindgren
2018-05-17 16:38 ` Andy Shevchenko
2018-05-17 19:30 ` Tony Lindgren
2018-05-22 21:39 ` Andy Shevchenko [this message]
2018-05-23 17:58 ` Tony Lindgren
2018-05-23 18:32 ` Tony Lindgren
2018-07-18 15:14 ` Andy Shevchenko
2018-07-19 6:47 ` Tony Lindgren
2018-05-17 17:04 ` Tony Lindgren
2018-05-17 13:48 ` Tony Lindgren
2018-05-17 16:36 ` Andy Shevchenko
2018-05-17 19:48 ` Tony Lindgren
2018-05-22 21:52 ` Andy Shevchenko
2018-05-23 18:00 ` Tony Lindgren
2018-07-18 14:50 ` Andy Shevchenko
2018-07-19 6:50 ` Tony Lindgren
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