On Thu, May 17, 2018 at 10:30 PM, Tony Lindgren <tony@xxxxxxxxxxx> wrote: > * Andy Shevchenko <andy.shevchenko@xxxxxxxxx> [180517 16:41]: >> On Thu, May 17, 2018 at 4:56 PM, Tony Lindgren <tony@xxxxxxxxxxx> wrote: >> > * Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> [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 -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
