Messages in this thread | | | Date | Thu, 26 Apr 2012 11:56:51 +0100 | From | Catalin Marinas <> | Subject | Re: [PATCH] ARM: cache-l2x0.c: save aux ctrl for resume in case that l2x0 is enabled before init |
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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.
-- Catalin
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