On Mon, Apr 28, 2014 at 12:08:11PM -0600, Stephen Warren wrote: > (Dropping most people from CC since this sub-thread is a Tegra-specific > discussion) > > On 04/28/2014 11:39 AM, Russell King - ARM Linux wrote: > > On Mon, Apr 28, 2014 at 11:27:09AM -0600, Stephen Warren wrote: > ... > >> I do see one error in dmesg during boot, but it doesn't appear to > >> negatively affect operation in brief testing, and is present in > >> linux-next without this series anyway. Is this message a problem? > >> > >>> [ 0.000000] L2C: platform modifies aux control register: 0x02080000 -> 0x3e480001 > >>> [ 0.000000] L2C: DT/platform modifies aux control register: 0x02080000 -> 0x3e480001 > >>> [ 0.000000] L2C-310 errata 727915 769419 enabled > >>> [ 0.000000] L2C-310 enabling early BRESP for Cortex-A9 > >>> [ 0.000000] L2C-310: enabling full line of zeros but not enabled in Cortex-A9 > >> ^^^^^^ this is logged at error level > > > > Correct, it's an error because on Tegra you explicitly set bit 0 in the > > auxiliary control register, which is pointless unless the feature is > > also enabled in the Cortex-A9 control register as well. > > Please forgive my almost complete lack of knowledge re: cache > controllers. Is the correct fix for this: > > a) To remove bit 0 from the aux_val passed to l2x0_of_init() > > b) To set some BIT(3) in the Cortex-A9 auxcr, so this feature is enabled > there too. > > And if (b), I assume that's something that the bootloader should be > doing, not the kernel? See "Full line of zero write." http://infocenter.arm.com/help/topic/com.arm.doc.ddi0246h/CJACBHHB.html#CJADBCJJ which makes it (a). The reverse steps are required when disabling the L2 cache controller. If we decide that we encounter a platform which needs this feature disabled, the correct way to deal with that is to add a L2C-310 specific property to DT, and not to try to crowbar it in via the L2C aux control register masks (which should never have been exposed to platforms using DT.) -- FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly improving, and getting towards what was expected from it. -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html