On 17.07.2014 17:51, Jason Cooper wrote: > On Thu, Jul 17, 2014 at 05:40:50PM +0200, Tomasz Figa wrote: >> Hi Jason, >> >> On 17.07.2014 17:32, Jason Cooper wrote: >>> On Thu, Jul 17, 2014 at 05:23:44PM +0200, Tomasz Figa wrote: >>>> Certain GIC implementation, namely those found on earlier, single >>>> cluster, Exynos SoCs, have registers mapped without per-CPU banking, >>>> which means that the driver needs to use different offset for each CPU. >>>> >>>> Currently the driver calculates the offset by multiplying value returned >>>> by cpu_logical_map() by CPU offset parsed from DT. This is correct when >>>> CPU topology is not specified in DT and aforementioned function returns >>>> core ID alone. However when DT contains CPU topology, the function >>>> changes to return cluster ID as well, which is non-zero on mentioned >>>> SoCs and so breaks the calculation in GIC driver. >>>> >>>> This patch fixes this by masking out cluster ID in CPU offset >>>> calculation so that only core ID is considered. Multi-cluster Exynos >>>> SoCs already have banked GIC implementations, so this simple fix should >>>> be enough. >>>> >>>> Reported-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> >>>> Reported-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@xxxxxxxxxxx> >>>> Signed-off-by: Tomasz Figa <t.figa@xxxxxxxxxxx> >>>> --- >>>> drivers/irqchip/irq-gic.c | 5 ++++- >>>> 1 file changed, 4 insertions(+), 1 deletion(-) >>> >>> iiuc, this was introduced by: >>> >>> db0d4db22a78d ARM: gic: allow GIC to support non-banked setups >>> >>> and so should be for v3.3 and up, correct? >> >> Could be, although there was and still is no topology data specified in >> DT for affected Exynos SoCs. The need for it showed up just recently, so >> I'm not sure this is a regression to fix in older kernels. > > In my "the kernel and the dtb aren't tied together" quest, these are the > kinds of things I like to see fixed in stable kernels. > > If a user needs to update a dtb, say to fix a bug, it's reasonable to > use the newest one for a given board. After all, any new nodes won't > change anything, since the driver in the kernel won't match the node. > > However, in this case, without this fix, a user upgrading to the newest > dtb would get a broken system. So, this fix should be backported to > prevent the breakage. Or, have I missed something in my analysis? This is correct when looking only at this issue. However I suspect such move would cause a breakage anyway, because DT stuff isn't that stable on Exynos side. I don't mind if this patch hits stable, though. Best regards, Tomasz -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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