Re: [PATCH v3 1/4] cpuidle: qcom-spm: Check if any CPU is managed by SPM

From: Marek Szyprowski <m.szyprowski@samsung.com>
To: Stephan Gerhold <stephan@gerhold.net>,
	Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>,
	linux-arm-msm@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org,
	Arnd Bergmann <arnd@arndb.de>, Andy Gross <agross@kernel.org>
Subject: Re: [PATCH v3 1/4] cpuidle: qcom-spm: Check if any CPU is managed by SPM
Date: Wed, 1 Dec 2021 18:05:47 +0100	[thread overview]
Message-ID: <687ec764-78b4-4929-f9ec-373254d160a7@samsung.com> (raw)
In-Reply-To: <20211201130505.257379-2-stephan@gerhold.net>

On 01.12.2021 14:05, Stephan Gerhold wrote:
> At the moment, the "qcom-spm-cpuidle" platform device is always created,
> even if none of the CPUs is actually managed by the SPM. On non-qcom
> platforms this will result in infinite probe-deferral due to the
> failing qcom_scm_is_available() call.
>
> To avoid this, look through the CPU DT nodes and check if there is
> actually any CPU managed by a SPM (as indicated by the qcom,saw property).
> It should also be available because e.g. MSM8916 has qcom,saw defined
> but it's typically not enabled with ARM64/PSCI firmwares.
>
> This is needed in preparation of a follow-up change that calls
> qcom_scm_set_warm_boot_addr() a single time before registering any
> cpuidle drivers. Otherwise this call might be made even on devices
> that have this driver enabled but actually make use of PSCI.
>
> Fixes: 60f3692b5f0b ("cpuidle: qcom_spm: Detach state machine from main SPM handling")
> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Link: https://lore.kernel.org/r/86e3e09f-a8d7-3dff-3fc6-ddd7d30c5d78@samsung.com/
> Signed-off-by: Stephan Gerhold <stephan@gerhold.net>

I'm fine with this fix.

Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>

> ---
> Daniel, would be great if you could ack this patch and PATCH 3/4
> (the cpuidle part) if they look good to you. I think it's easiest if Bjorn
> takes them together with the qcom_scm changes through the qcom tree.
>
> Marek had an alternative fix for this [1], the difference in this patch is
> that it avoids creating the platform device entirely if no CPU is managed
> by a SPM.
>
> [1]: https://lore.kernel.org/r/20211020120643.28231-1-m.szyprowski@samsung.com/
> ---
>   drivers/cpuidle/cpuidle-qcom-spm.c | 20 ++++++++++++++++++++
>   1 file changed, 20 insertions(+)
>
> diff --git a/drivers/cpuidle/cpuidle-qcom-spm.c b/drivers/cpuidle/cpuidle-qcom-spm.c
> index 01e77913a414..5f27dcc6c110 100644
> --- a/drivers/cpuidle/cpuidle-qcom-spm.c
> +++ b/drivers/cpuidle/cpuidle-qcom-spm.c
> @@ -155,6 +155,22 @@ static struct platform_driver spm_cpuidle_driver = {
>   	},
>   };
>   
> +static bool __init qcom_spm_find_any_cpu(void)
> +{
> +	struct device_node *cpu_node, *saw_node;
> +
> +	for_each_of_cpu_node(cpu_node) {
> +		saw_node = of_parse_phandle(cpu_node, "qcom,saw", 0);
> +		if (of_device_is_available(saw_node)) {
> +			of_node_put(saw_node);
> +			of_node_put(cpu_node);
> +			return true;
> +		}
> +		of_node_put(saw_node);
> +	}
> +	return false;
> +}
> +
>   static int __init qcom_spm_cpuidle_init(void)
>   {
>   	struct platform_device *pdev;
> @@ -164,6 +180,10 @@ static int __init qcom_spm_cpuidle_init(void)
>   	if (ret)
>   		return ret;
>   
> +	/* Make sure there is actually any CPU managed by the SPM */
> +	if (!qcom_spm_find_any_cpu())
> +		return 0;
> +
>   	pdev = platform_device_register_simple("qcom-spm-cpuidle",
>   					       -1, NULL, 0);
>   	if (IS_ERR(pdev)) {

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland