On Wed, May 16, 2018 at 1:08 PM, Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote: > On 2018-05-15 21:37:18 [+0300], Andy Shevchenko wrote: >> On Tue, 2018-05-15 at 21:34 +0300, Andy Shevchenko wrote: >> > Kernel console is sensitive to any kind of complex work needed to >> > print >> > out anything on it. One such case is emergency print during Oops. >> > >> > This series proposes to disable runtime PM and DMA operations on 8250 >> > serial console. >> > >> > More detailed explanation why is provided in patch 2. >> > >> > The series has been in our internal trees for years already with no >> > problems observed. >> >> +Cc: Tony. >> >> You might have some thoughts / test means for this. > > I haven't look at the patches, just your cover letter. Disabling DMA on > kernel-console should be fine. Would you mind to give an Ack for it? > The output is usually short so there > shouldn't be much benefit from using it. > I remember Tony wanted runtime-pm on the kernel console, too. And he > told me explicit how to test it so that it works. Once the UART goes > into PM (down), the whole IP block can go into power save mode. The > board can be woken up by sending a character via the UART. The first few > (incoming / read) characters are lost until the IP block is up again the > frequency stable. This is known / expected. Don't consider world the OMAP only. The things more complicated if we go out of it. Which I tried to explain in the commit message of patch 2. > In order to achieve the same thing you would have to disable the kernel > console on that UART. I leave this to Tony. Precisely the point of the series. -- 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
