On 11/6/2015 1:55 AM, Hauke Mehrtens wrote: > On 11/05/2015 10:34 AM, Russell King - ARM Linux wrote: >> On Thu, Nov 05, 2015 at 12:51:17AM -0500, Kapil Hali wrote: >>> Hi, >>> >>> This series adds SMP support for Broadcom's Northstar Plus SoC. >>> >>> There are similar SMP enablement methods for many ARMv7 bsed SoCs. >>> BCM NSP SoC, has a typical such mechanism - after power-on, the >>> secondary core is held in a standby state, primary core provides a >>> startup address for the secondary core and wakes it up. Booting of >>> the secondary core is serialized using pen_release global variable. >> >> Why do you need the pen_release stuff? The above implies that you >> have only one secondary core, and you can control when it comes out >> of standby state. >> >> Please, don't assume that the pen_release stuff is any kind of recommended >> or standardised system. It isn't. It's a hack for ARMs evaluation >> platforms. >> > > I tried to remove the pen code because I also thought/hoped that it is > useless, but the 2. CPU did not boot any more after I removed it. I do > not know the internals of SoC, but it looks like this is needed. > > I described it here: > http://www.spinics.net/lists/arm-kernel/msg452178.html > > I removed this comparison and the jump afterwards ("cmp r7, r0") and > the 2. CPU did not boot any more. Is this pen stuff some kind of > workaround for some bug in the silicon? > pen stuff is not a work around for any bug in BCM NSP silicon. It was the mechanism to bring-up SMP on some of the ARM based SoCs and many silicon vendors seem to consider it as a generic mechanism for controlled bring-up of SMP. But as is clear from Russel King's comments, it is not a standardized recommended method. Also, I removed the pen_release method and it works on BCM NSP SoCs. I will add the changes in the next patch set. > Hauke > Thanks, Kapil Hali -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
