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Date: Thu, 26 Apr 2012 11:28:15 +0100 From: Catalin Marinas <catalin.marinas@....com> To: Yilu Mao <ylmao@...vell.com> Cc: "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> Subject: Re: [PATCH] ARM: cache-l2x0.c: save aux ctrl for resume in case that l2x0 is enabled before init 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. -- Catalin -- 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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