linux-kernel - Re: [PATCH v6 20/25] drivers: firmware: psci: Introduce psci_dt_topology

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Date:   Wed, 14 Mar 2018 17:38:33 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Sudeep Holla <sudeep.holla@....com>,
        Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
        linux-pm@...r.kernel.org, Kevin Hilman <khilman@...nel.org>,
        Lina Iyer <ilina@...eaurora.org>,
        Lina Iyer <lina.iyer@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Juri Lelli <juri.lelli@....com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 20/25] drivers: firmware: psci: Introduce
 psci_dt_topology_init()

On Wed, Mar 14, 2018 at 05:58:30PM +0100, Ulf Hansson wrote:
> In case the hierarchical layout is used in DT, we want to initialize the
> corresponding PM domain topology for the CPUs, by using the generic PM
> domain (aka genpd) infrastructure.
> 
> At first glance, it may seem feasible to hook into the existing
> psci_dt_init() function, although because it's called quite early in the
> boot sequence, allocating the dynamic data structure for a genpd doesn't
> work.
> 
> Therefore, let's export a new init function for PSCI,
> psci_dt_topology_init(), which the ARM machine code should call from a
> suitable initcall.
> 
> Succeeding to initialize the PM domain topology, which means at least one
> instance of a genpd becomes created, allows us to continue to enable the
> PSCI OS initiated mode for the platform. If everything turns out fine,
> let's print a message in log to inform the user about the changed mode.
> 
> In case of any failures, we stick to the default PSCI Platform Coordinated
> mode.

For kexec/kdump we'll need to explicitly set the suspend mode to
platform coordinated if for whatever reason we choose not to use OSI.

> 
> Cc: Lina Iyer <ilina@...eaurora.org>
> Co-developed-by: Lina Iyer <lina.iyer@...aro.org>
> Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
> ---
>  drivers/firmware/psci.c | 31 +++++++++++++++++++++++++++++++
>  include/linux/psci.h    |  2 ++
>  2 files changed, 33 insertions(+)
> 
> diff --git a/drivers/firmware/psci.c b/drivers/firmware/psci.c
> index 463f78c..45d55fc 100644
> --- a/drivers/firmware/psci.c
> +++ b/drivers/firmware/psci.c
> @@ -723,6 +723,37 @@ int __init psci_dt_init(void)
>  	return ret;
>  }
>  
> +int __init psci_dt_topology_init(void)
> +{
> +	struct device_node *np;
> +	int ret;
> +
> +	if (!psci_has_osi_support())
> +		return 0;
> +
> +	np = of_find_matching_node_and_match(NULL, psci_of_match, NULL);
> +	if (!np)
> +		return -ENODEV;
> +
> +	/* Initialize the CPU PM domains based on topology described in DT. */
> +	ret = psci_dt_init_pm_domains(np);
> +	if (ret <= 0)
> +		goto out;
> +
> +	/* Enable OSI mode. */
> +	ret = invoke_psci_fn(PSCI_1_0_FN_SET_SUSPEND_MODE,
> +			     PSCI_1_0_SUSPEND_MODE_OSI, 0, 0);

IIUC, this patch will need to be moved after the subsequent two patches
to ensure that this series bisects cleanly.

Thanks,
Mark.