Hi Steffen, On Thu, 25 Sep 2014, Steffen Trumtrar wrote:
> Hi! > > On Wed, Sep 24, 2014 at 03:27:29PM -0500, at...@opensource.altera.com wrote: > > From: Alan Tull <at...@opensource.altera.com> > > > > Add code that requests that the sdr controller go into > > self-refresh mode. This code is run from ocram. > > > > This patch assumes that u-boot has already configured sdr: > > sdr.ctrlcfg.lowpwreq.selfrfshmask = 3 > > sdr.ctrlcfg.lowpwrtiming.clkdisablecycles = 8 > > sdr.ctrlcfg.dramtiming4.selfrfshexit = 512 > > > > How to suspend to ram: > > $ echo enabled > \ > > /sys/devices/soc/ffc02000.serial0/tty/ttyS0/power/wakeup > > > > $ echo -n mem > /sys/power/state > > > > (...) > > Never looked into that, so maybe a stupid question: > What happens if the bootloader (u-boot or other) didn't configure the sdr? > Will it "just" not wake up again? Waking up won't be the problem. Linux won't boot. Alternatively, if this Linux kernel is paired with a version of the bootloader that does most of the initializion, but not the settings that we want here, I expect there could be issues. I don't want to duplicate the u-boot sdr configuration code, instead I document my assumptions here here. For future generations who take this patch. If they have a problem with s2r, they will look through the git logs and find this helpful note of what their bootloader was supposed to do. Alan > > Regards, > Steffen > > -- > Pengutronix e.K. | | > Industrial Linux Solutions | http://www.pengutronix.de/ | > Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | > Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
