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Date: Sat, 28 Apr 2012 14:24:28 +0800 From: Yilu Mao <ylmao@...vell.com> To: Lu Mao <ylmao@...vell.com> CC: Catalin Marinas <catalin.marinas@....com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux@....linux.org.uk" <linux@....linux.org.uk>, "Baohua.Song@....com" <Baohua.Song@....com>, "santosh.shilimkar@...com" <santosh.shilimkar@...com>, "robherring2@...il.com" <robherring2@...il.com>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, Ning Jiang <njiang1@...vell.com> Subject: Re: [PATCH] ARM: cache-l2x0.c: save aux ctrl for resume in case that l2x0 is enabled before init On 04/26/2012 07:03 PM, Lu Mao wrote: > On 04/26/2012 06:56 PM, Catalin Marinas wrote: >> On Thu, Apr 26, 2012 at 11:48:18AM +0100, Yilu Mao wrote: >>> On 04/26/2012 06:38 PM, Catalin Marinas wrote: >>>> On Thu, Apr 26, 2012 at 11:35:39AM +0100, Yilu Mao wrote: >>>>> On 04/26/2012 06:28 PM, Catalin Marinas wrote: >>>>>> On Thu, Apr 26, 2012 at 11:09:26AM +0100, Yilu Mao wrote: >>>>>>> On 04/26/2012 05:44 PM, Catalin Marinas wrote: >>>>>>>> On Thu, Apr 26, 2012 at 10:25:31AM +0100, Yilu Mao wrote: >>>>>>>>> On 04/26/2012 04:35 PM, Catalin Marinas wrote: >>>>>>>>>> On Thu, Apr 26, 2012 at 06:00:09AM +0100, Yilu Mao wrote: >>>>>>>>>>> On 04/24/2012 04:28 PM, Catalin Marinas wrote: >>>>>>>>>>>> On Tue, Apr 24, 2012 at 03:41:20AM +0100, Yilu Mao wrote: >>>>>>>>>>>>> + l2x0_saved_regs.aux_ctrl = aux; >>>>>>>>>>>>> + >>>>>>>>>>>>> aux&= aux_mask; >>>>>>>>>>>>> aux |= aux_val; >>>>>>>>>>>> >>>>>>>>>>>> I think that's the wrong place to save it, it should be after the >>>>>>>>>>>> masking was done. >>>>>>>>>>>> >>>>>>>>>>>> Anyway, if we cannot write this register in l2x0_init() because the L2 >>>>>>>>>>>> was enabled, do we expect the L2 to be disabled during resume? >>>>>>>>>>>> >>>>>>>>>>> Sorry, I don't think so. >>>>>>>>>>> This is the right place to save it because we must make sure the saved >>>>>>>>>>> aux_ctrl is the same as what it is set. >>>>>>>>>>> If we save it after masking was done, the saved value will be different >>>>>>>>>>> because we can't actually change the real setting. >>>>>>>>>> >>>>>>>>>> And since we can't actually change the real setting on the resume path, >>>>>>>>>> why do we need to save it anyway. Is your L2 cache disabled on the >>>>>>>>>> resume path but not on the cold boot one? >>>>>>>>> >>>>>>>>> We can't change L2 aux ctrl setting when do init because it has been >>>>>>>>> enabled. >>>>>>>> >>>>>>>> This is normally for the case where the kernel running in non-secure >>>>>>>> mode is not allowed to write the L2 aux ctrl register. Does this >>>>>>>> permission change with core idle? >>>>>>>> >>>>>>> Yes, your understanding of previous mail is right. The L2 is enabled on >>>>>>> code boot and it is disabled on the resume in our case. >>>>>> >>>>>> But the kernel either runs in secure mode or the non-secure access to >>>>>> this register is allowed. >>>>>> >>>>>>> So if we don't have such patch, when core idle exit, L2 cache aux ctrl >>>>>>> register will be set to 0x0 because l2x0_saved_regs.aux_ctrl is not >>>>>>> initialized. >>>>>> >>>>>> You could still make sure that the mask passed doesn't affect the >>>>>> original setting and save it after masking. >>>>>> >>>>> Do you mean the code is like this: >>>>> aux = readl_relaxed(l2x0_base + L2X0_AUX_CTRL); >>>>> aux&= aux_mask; >>>>> l2x0_saved_regs.aux_ctrl = aux; >>>>> >>>>> Then the saved value is not the same as real setting. So the restored >>>>> value after core idle will not the same as before... This is not what we >>>>> expected. >>>> >>>> My point was that on your platform you pass an aux_mask that is meant to >>>> change the already set aux_ctlr value. Why do you pass such mask to be >>>> anything other than ~0UL in this case? >>>> >>> Sorry I still can't catch your point... >>> In our platform, we actually use ~0UL as aux mask. >>> >>> Anyway, the two arguments, aux_value and aux_mask, are both for changing >>> the original value set before kernel bootup. If L2 cache is enabled in >>> cold boot, both two arguments are useless because we can't set the >>> register. So we must make sure we can restore the original value after >>> core idle. >> >> So if your platform passes aux_mask = ~0UL and aux_val = 0, there is no >> change to the read aux_ctlr value. >> >> If for whatever reason (same binary running in different configuration) >> you need to pass the aux_mask and aux_val different from the above, then >> your argument makes sense. But I just want to be clear. >> > Actually, our arguments are aux_value = 0x30000000 and aux_mask = ~0UL. > I think it is also ok with my patch. > What do you think? > Hi Catalin, Do you agree with this patch to be merged? -- Thanks. Best Wishes, Yilu Mao -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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