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Date: Mon, 8 Jul 2019 14:20:02 +0200
From: Martin Kepplinger <martink@...teo.de>
To: Abel Vesa <abel.vesa@....com>
Cc: Mark Rutland <mark.rutland@....com>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
Jacky Bai <ping.bai@....com>,
Carlo Caione <ccaione@...libre.com>,
Marc Zyngier <marc.zyngier@....com>,
Shawn Guo <shawnguo@...nel.org>,
Sascha Hauer <s.hauer@...gutronix.de>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Rob Herring <robh+dt@...nel.org>,
dl-linux-imx <linux-imx@....com>,
Pengutronix Kernel Team <kernel@...gutronix.de>,
Abel Vesa <abelvesa@...il.com>,
Thomas Gleixner <tglx@...utronix.de>,
Leonard Crestez <leonard.crestez@....com>,
Fabio Estevam <festevam@...il.com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
Lucas Stach <l.stach@...gutronix.de>
Subject: Re: [RFC 0/2] Add workaround for core wake-up on IPI for i.MX8MQ
On 08.07.19 09:54, Martin Kepplinger wrote:
> 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?
>
looks like I mess things up myself here and somehow prevent
cpu_pm_enter() from being called...
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