Messages in this thread | | | From | Andy Shevchenko <> | Date | Wed, 23 May 2018 00:52:01 +0300 | Subject | Re: [PATCH v1 0/3] console, serial8250: Disable PM and DMA ops |
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On Thu, May 17, 2018 at 10:48 PM, Tony Lindgren <tony@atomide.com> wrote: > * Andy Shevchenko <andy.shevchenko@gmail.com> [180517 16:38]: >> On Thu, May 17, 2018 at 4:48 PM, Tony Lindgren <tony@atomide.com> wrote: >> > * Sebastian Andrzej Siewior <bigeasy@linutronix.de> [180516 10:49]:
>> > The idea breaking PM seems silly to me considering that we've had >> > it working for years already. >> >> Same question / note. World is much more complex than just being OMAP. > > Sorry but you are making assumptions about hardware being powered on > all the time.
Nope, other way around. The so called "support" _prevents_ our hardware to go to sleep.
So it's not breaking, it's fixing. It's pity that OMAP solution is just a hack.
> It may have been a safe assumption up to mid-90's and might still be > valid assumption for hardware providing on MS-DOS boot floppy > compability. > > But that is not a safe assumption for Linux kernel at all. Especially > for console TX where there's no need to keep it powered unless there > is actually something to write. > > If there are runtime PM issues for consoles, let's just fix them.
Yes, there is an issue to begin with, i.e. irq_safe hack. Removal of that hack reveals the real issues with the code.
> Then for really seeing console messages on next reboot from a hung > system, CONFIG_PSTORE_CONSOLE option seems to do a very good job.
How this helps to prevent a more serious system crashes during an attempt to power UART on?
> With a warm reset after triggered by watchdog the console messages > are readable most of the time even when using DDR as the back end.
Ditto.
-- With Best Regards, Andy Shevchenko
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