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Message-ID: <20150130101709.GB8787@red-moon> Date: Fri, 30 Jan 2015 10:17:09 +0000 From: Lorenzo Pieralisi <lorenzo.pieralisi@....com> To: "Yang, Wenyou" <Wenyou.Yang@...el.com> Cc: "Ferre, Nicolas" <Nicolas.FERRE@...el.com>, "linux@....linux.org.uk" <linux@....linux.org.uk>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "alexandre.belloni@...e-electrons.com" <alexandre.belloni@...e-electrons.com>, "sylvain.rochet@...secur.com" <sylvain.rochet@...secur.com>, "peda@...ntia.se" <peda@...ntia.se>, "Vilchez, Patrice" <Patrice.VILCHEZ@...el.com> Subject: Re: [PATCH 2/7] pm: at91: pm_suspend: add the WFI support for ARMv7 On Fri, Jan 30, 2015 at 07:23:21AM +0000, Yang, Wenyou wrote: [...] > > > > > + * Put the processor to enter the WFI state */ > > > > > + .macro _do_wfi > > > > > > > > You will have to explain why you need this, really. > > > I don't understand your meaning. > > > > I want to understand why this assembly snippet (that can be rewritten in C BTW): > > > > /* Disable the processor's clock */ > > mov tmp1, #AT91_PMC_PCK > > str tmp1, [pmc, #AT91_PMC_SCDR] > > > > + > > > > cpu_do_idle() > > > > is not sufficient for you, or put it differently, why do you need this macro. > This assembly snippet will be copied and run in the SRAM, in the period the DDR is in the self-refresh state. > So, it can't invoke other functions generally. Ok, thanks for explaining, I will have a look again to check where you use the macro to verify the code flow. > > > > > > > > > > > > > > > + > > > > > +#if defined(CONFIG_CPU_V7) > > > > > + /* > > > > > + * Execute an ISB instruction to flush the pipeline to ensure > > > > > + * that all of operations have beem completed. > > > > > > > > s/beem/been > > > Thanks. > > > > > > > > > > > > + */ > > > > > + isb > > > > This isb should not be there, unless you know a reason why it should and you > > explain it to me. > I encountered system lock during verifying the pm function. > Anyway, I will tested again whether it works after removing it. See above, I have to check when you switch to SRAM execution to see if an isb is appropriate there, it is not self-explanatory. Thank you, Lorenzo > > > > > > > > + > > > > > + /* > > > > > + * Execute an ISB instruction to ensure that all of the > > > > > + * CP15 register changes have been committed. > > > > > + */ > > > > > + dsb > > > > > > > > This is a dsb not an isb. > > > Changed in the v2.0 > > > > Yes, but I still do not understand why you want to execute it before disabling the > > clocks (I really hope that by "disabling the clocks" you mean "set the power > > controller to a state when, on wfi execution, the clocks are gated"). > Are you meaning to execute dsb and wfi after disabling the clocks? > > > > > > > > > > > > > > > + dmb > > > > > > > > You have to explain why you need every single one of these barriers, > > > > otherwise I am NAKing this patch. > > > No need this one? > > > > No, remove it. > OK, thanks > > > > > > > > > > > > > > > + > > > > > + /* Disable the processor's clock */ > > > > > + mov tmp1, #AT91_PMC_PCK > > > > > + str tmp1, [pmc, #AT91_PMC_SCDR] > > > > > + > > > > > + /* Execute a WFI instruction */ > > > > > + wfi @ Wait For Interrupt > > > > > > > > This one looks ok :) > > > > > > > > > + > > > > > + /* > > > > > + * CPU can specualatively prefetch the instructions > > > > > + * so add NOPs after WFI. Sixteen NOPs as Cortex-A5 pipeline. > > > > > > > > So what ? I suspect your issue is related to wfi completion on > > > > pending IRQ. I would like to know the details that describe the > > > > issue you are trying to solve here please. > > > Honestly, I referred to others, I will dig more, and test it. > > > > You should not copy and paste code, because: > > > > 1) it might be broken > > 2) and/or unoptimized > > 3) and/or does not apply to your platform > > > > See my suggestion above, if it does not work for you, you will report the issue and > > we will take it from there. > OK, thanks. > > > > > Thanks, > > Lorenzo > > > > > > > > > > > > > > + */ > > > > > + nop > > > > > + nop > > > > > + nop > > > > > + nop > > > > > + nop > > > > > + nop > > > > > + nop > > > > > + nop > > > > > + nop > > > > > + nop > > > > > + nop > > > > > + nop > > > > > + nop > > > > > + nop > > > > > + nop > > > > > + nop > > > > > +#else > > > > > + mcr p15, 0, tmp1, c7, c0, 4 > > > > > +#endif > > > > > > > > Tell us what's the problem you have to solve, first, then we will see how to fix it. > > > > > > > > Thanks, > > > > Lorenzo > > > > > > > > > + > > > > > + .endm > > > > > + > > > > > .text > > > > > > > > > > /* > > > > > @@ -181,7 +233,7 @@ sdr_sr_done: > > > > > > > > > > skip_disable_main_clock: > > > > > /* Wait for interrupt */ > > > > > - mcr p15, 0, tmp1, c7, c0, 4 > > > > > + _do_wfi > > > > > > > > > > tst mode, #AT91_PM_SLOW_CLOCK > > > > > beq skip_enable_main_clock > > > > > -- > > > > > 1.7.9.5 > > > > > > > > > > -- > > > > > 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/ > > > > > > > > > > > Best Regards, > > > Wenyou Yang > > > > > Best Regards, > Wenyou Yang > -- 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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