linux-kernel - Re: [PATCH v6 1/5] cpuidle: qcom_spm: Detach state machine from main SPM handling

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Date:   Tue, 22 Jun 2021 13:39:15 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>
To:     Stephan Gerhold <stephan@...hold.net>
Cc:     bjorn.andersson@...aro.org, agross@...nel.org,
        daniel.lezcano@...aro.org, rjw@...ysocki.net,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, phone-devel@...r.kernel.org,
        konrad.dybcio@...ainline.org, marijn.suijten@...ainline.org,
        martin.botka@...ainline.org, jeffrey.l.hugo@...il.com,
        jami.kettunen@...ainline.org,
        ~postmarketos/upstreaming@...ts.sr.ht, devicetree@...r.kernel.org,
        robh+dt@...nel.org
Subject: Re: [PATCH v6 1/5] cpuidle: qcom_spm: Detach state machine from main
 SPM handling

Il 21/06/21 23:08, Stephan Gerhold ha scritto:
> On Mon, Jun 21, 2021 at 08:10:12PM +0200, AngeloGioacchino Del Regno wrote:
>> In commit a871be6b8eee ("cpuidle: Convert Qualcomm SPM driver to a generic
>> CPUidle driver") the SPM driver has been converted to a
>> generic CPUidle driver: that was mainly made to simplify the
>> driver and that was a great accomplishment;
>> Though, it was ignored that the SPM driver is not used only
>> on the ARM architecture.
>>
> 
> I don't really understand why you insist on writing that I deliberately
> "ignored" your use case when converting the driver. This is not true.
> Perhaps that's not actually what you meant but that's how it sounds to
> me.
> 

So much noise for one single word. I will change it since it seems to be
that much of a deal, and I'm sorry if that hurt you in any way.

For the records, though, I really don't see anything offensive in that,
and anyway I didn't mean to be offensive in any way.

>> In preparation for the enablement of SPM features on AArch64/ARM64,
>> split the cpuidle-qcom-spm driver in two: the CPUIdle related
>> state machine (currently used only on ARM SoCs) stays there, while
>> the SPM communication handling lands back in soc/qcom/spm.c and
>> also making sure to not discard the simplifications that were
>> introduced in the aforementioned commit.
>>
>> Since now the "two drivers" are split, the SCM dependency in the
>> main SPM handling is gone and for this reason it was also possible
>> to move the SPM initialization early: this will also make sure that
>> whenever the SAW CPUIdle driver is getting initialized, the SPM
>> driver will be ready to do the job.
>>
>> Please note that the anticipation of the SPM initialization was
>> also done to optimize the boot times on platforms that have their
>> CPU/L2 idle states managed by other means (such as PSCI), while
>> needing SAW initialization for other purposes, like AVS control.
>>
>> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...ainline.org>
>> ---
>>   drivers/cpuidle/Kconfig.arm        |   1 +
>>   drivers/cpuidle/cpuidle-qcom-spm.c | 324 +++++++----------------------
>>   drivers/soc/qcom/Kconfig           |   9 +
>>   drivers/soc/qcom/Makefile          |   1 +
>>   drivers/soc/qcom/spm.c             | 198 ++++++++++++++++++
>>   include/soc/qcom/spm.h             |  41 ++++
>>   6 files changed, 325 insertions(+), 249 deletions(-)
>>   create mode 100644 drivers/soc/qcom/spm.c
>>   create mode 100644 include/soc/qcom/spm.h
>>
>> diff --git a/drivers/cpuidle/cpuidle-qcom-spm.c b/drivers/cpuidle/cpuidle-qcom-spm.c
>> index adf91a6e4d7d..091453135ea6 100644
>> --- a/drivers/cpuidle/cpuidle-qcom-spm.c
>> +++ b/drivers/cpuidle/cpuidle-qcom-spm.c
>> [...]
>> +static int spm_cpuidle_register(int cpu)
>>   {
>> +	struct platform_device *pdev = NULL;
>> +	struct device_node *cpu_node, *saw_node;
>> +	struct cpuidle_qcom_spm_data data = {
>> +		.cpuidle_driver = {
>> +			.name = "qcom_spm",
>> +			.owner = THIS_MODULE,
>> +			.cpumask = (struct cpumask *)cpumask_of(cpu),
>> +			.states[0] = {
>> +				.enter			= spm_enter_idle_state,
>> +				.exit_latency		= 1,
>> +				.target_residency	= 1,
>> +				.power_usage		= UINT_MAX,
>> +				.name			= "WFI",
>> +				.desc			= "ARM WFI",
>> +			}
>> +		}
>> +	};
> 
> The stack is gone after the function returns.
> 

Argh, I wrongly assumed that cpuidle was actually copying this locally.
Okay, let's see what else looking clean I can come up with.