On 12/06/2012 12:22 AM, Joseph Lo wrote: > On Thu, 2012-12-06 at 06:18 +0800, Stephen Warren wrote: >> On 12/05/2012 03:01 AM, Joseph Lo wrote: >>> The powered-down state of Tegra20 requires power gating both CPU cores. >>> When the secondary CPU requests to enter powered-down state, it saves >>> its own contexts and then enters WFI. The Tegra20 had a limition to >>> power down both CPU cores. The secondary CPU must waits for CPU0 in >>> powered-down state too. If the secondary CPU be woken up before CPU0 >>> entering powered-down state, then it needs to restore its CPU states >>> and waits for next chance. >>> >>> Be aware of that, you may see the legacy power state "LP2" in the code >>> which is exactly the same meaning of "CPU power down".
>>> diff --git a/arch/arm/mach-tegra/sleep-tegra20.S >>> b/arch/arm/mach-tegra/sleep-tegra20.S >> >>> +/* >>> + * tegra_pen_lock >> >>> + * on cpu 0: >>> + * SCRATCH38 = r2 = flag[0] >>> + * SCRATCH39 = r3 = flag[1] >> >> It would be slightly clearer if that was written: >> >> * r2 = flag[0] (in SCRATCH38) >> * r3 = flag[1] (in SCRATCH39) >> >> since the meaning of r2/r3 is what's being selected. >> > OK. Will fix. > >>> + mov r12, #1 >>> + str r12, [r2] @ flag[cpu] = 1 So here I can see we should hard-code the value that's written >>> + dsb >>> + str r12, [r1] @ !turn = cpu But here we're also writing "1" always, whereas the comment says it's writing "cpu", and given the algorithm description, I would expect to write "cpu" here not "1". >> Should that be "str r0, [r1]"? Otherwise, you're always writing 1 there, >> not writing the CPU ID as expected. > > The CPU_ID was not used to lock or un-lock the flag. Wriging 1 to lock > and 0 to release. -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
