Re: [RFC 0/2] Add workaround for core wake-up on IPI for i.MX8MQ
From: Martin Kepplinger
Date: Mon Jul 08 2019 - 03:54:25 EST
On 02.07.19 13:33, Abel Vesa wrote:
> On 19-07-02 08:47:19, Martin Kepplinger wrote:
>> On 28.06.19 10:54, Abel Vesa wrote:
>>> On 19-06-23 13:47:26, Martin Kepplinger wrote:
>>>> On 10.06.19 14:13, Abel Vesa wrote:
>>>>> This is another alternative for the RFC:
>>>>> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flkml.org%2Flkml%2F2019%2F3%2F27%2F545&data=02%7C01%7Cabel.vesa%40nxp.com%7Ccfc582f9977d479b7dda08d6feb9258a%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C636976468485275045&sdata=L%2Byn29%2FBS3KMjm9eCPBTZBTl30PmZywSjIj11bMQw5c%3D&reserved=0
>>>>>
>>>>> This new workaround proposal is a little bit more hacky but more contained
>>>>> since everything is done within the irq-imx-gpcv2 driver.
>>>>>
>>>>> Basically, it 'hijacks' the registered gic_raise_softirq __smp_cross_call
>>>>> handler and registers instead a wrapper which calls in the 'hijacked'
>>>>> handler, after that calling into EL3 which will take care of the actual
>>>>> wake up. This time, instead of expanding the PSCI ABI, we use a new vendor SIP.
>>>>>
>>>>> I also have the patches ready for TF-A but I'll hold on to them until I see if
>>>>> this has a chance of getting in.
>>>>
>>>> Let's leave out of the picture for now, how generally applicable and
>>>> mergable your changes are. I'd like to reproduce what you do and test
>>>> cpuidle on imx8mq:
>>>>
>>>> When applying your changes here and the corresponding ATF changes (
>>>> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fabelvesa%2Farm-trusted-firmware%2Ftree%2Fimx8mq-err11171&data=02%7C01%7Cabel.vesa%40nxp.com%7Ccfc582f9977d479b7dda08d6feb9258a%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C636976468485275045&sdata=VT3duSl70DNxcY8Ev4FFrHlWoOjkcckeM8BgxrSkr8A%3D&reserved=0 if
>>>> I got that right) I don't yet see any difference in the SoC heating up
>>>> under zero load. __cpu_do_idle() is called about every 1ms (without your
>>>> changes, that was even more often but I'm not yet sure if that means
>>>> anything).
>>>
>>> You will most probably not see any change in the SoC temp since the cpuidle
>>> only touches the A53s. There are way many more IPs in the SoC that could
>>> heat it up. If you want some real numbers you'll have to measure the power
>>> consumtion on VDD_ARM rail. If you don't want to go through that much trouble
>>> you can use the idlestat tool to measure the times each A53 speends in cpu-sleep
>>> state.
>>>
>>>>
>>>> What I also see is that I get about 10x more "arch_timer" (int.3, GICv3)
>>>> interrupts than without your changes.
>>
>>
>> thanks for getting back at me here. This is run on the imx8mq
>> librem5-devkit with your wakeup-workaround applied. Typical measurements
>> under zero load look like this:
>>
>> sudo idlestat --trace -f /tmp/mytrace -t 10 -p -c -w
>> Log is 10.000395 secs long with 31194 events
>> ------------------------------------------------------------------------
>> | C-state | min | max | avg | total | hits | over | under |
>> ------------------------------------------------------------------------
>> | clusterA |
>> ------------------------------------------------------------------------
>> | WFI | 14us | 3.99ms | 3.90ms | 9.93s | 2543 | 0 | 0 |
>> ------------------------------------------------------------------------
>> | cpu0 |
>> ------------------------------------------------------------------------
>> | WFI | 14us | 3.99ms | 3.89ms | 9.96s | 2561 | 0 | 0 |
>> ------------------------------------------------------------------------
>> ...
>>
>
> I don't see the cpu-sleep state at all in your idlestat log. Maybe the cpuidle
> isn't enabled. Or probably the workaround itself is not applied. You'll have
> to look into that.
>
> Here is how it looks like with the workaround enabled:
>
> Log is 10.001685 secs long with 1175 events
> --------------------------------------------------------------------------------
> | C-state | min | max | avg | total | hits | over | under |
> --------------------------------------------------------------------------------
> | clusterA |
> --------------------------------------------------------------------------------
> | WFI | 2us | 50.04ms | 29.63ms | 9.99s | 337 | 0 | 0 |
> --------------------------------------------------------------------------------
> | cpu0 |
> --------------------------------------------------------------------------------
> | WFI | 11us | 50.04ms | 40.44ms | 9.62s | 238 | 0 | 219 |
> | cpu-sleep | 537us | 50.58ms | 14.11ms | 366.94ms | 26 | 7 | 0 |
> --------------------------------------------------------------------------------
> | cpu1 |
> --------------------------------------------------------------------------------
> | WFI | 11us | 539.04ms | 93.20ms | 5.78s | 62 | 0 | 38 |
> | cpu-sleep | 536us | 607.90ms | 183.38ms | 4.22s | 23 | 12 | 0 |
> --------------------------------------------------------------------------------
> | cpu2 |
> --------------------------------------------------------------------------------
> | WFI | 41us | 265.99ms | 17.51ms | 332.66ms | 19 | 0 | 11 |
> | cpu-sleep | 568us | 6.56s | 1.38s | 9.67s | 7 | 2 | 0 |
> --------------------------------------------------------------------------------
> | cpu3 |
> --------------------------------------------------------------------------------
> | WFI | 7.94ms | 881.50ms | 367.81ms | 1.10s | 3 | 0 | 3 |
> | cpu-sleep | 549us | 2.02s | 808.72ms | 8.90s | 11 | 1 | 0 |
> --------------------------------------------------------------------------------
>
> You can see that the cpu2 was once for 6.56 seconds (out of 10s) in cpu-sleep.
>
So I run this ATF tree
https://github.com/abelvesa/arm-trusted-firmware/tree/imx8mq-err11171
and, on top of "v5.2-rc7" I have your commits
("irqchip: irq-imx-gpcv2: Add workaround for i.MX8MQ ERR11171") and
("arm64: dts: imx8mq: Add idle states and gpcv2 wake_request broken
property") applied.
Then simply enabled CONFIG_ARM_CPUIDLE.
(I also use the "imx-cpufreq-dt" driver, but this should be unrelated here).
I do see the possible cpuidle states:
/sys/devices/system/cpu/cpu0/cpuidle$ cat state*/name
WFI
cpu-sleep
but idlestat doesn't see it or it is (thus) never used. Do you know a
needed change I might be missing?
thanks again,
martin