linux-kernel - Re: [PATCH v1] arch_topology: Adjust initial CPU capacities with current freq

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Date:   Fri, 10 Jan 2020 11:37:11 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Jeffy Chen <jeffy.chen@...k-chips.com>
Cc:     linux-kernel@...r.kernel.org,
        Brian Norris <briannorris@...omium.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Douglas Anderson <dianders@...omium.org>,
        Robin Murphy <robin.murphy@....com>,
        Heiko Stuebner <heiko@...ech.de>,
        Sudeep Holla <sudeep.holla@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH v1] arch_topology: Adjust initial CPU capacities with
 current freq

On Thu, Jan 09, 2020 at 03:52:14PM +0800, Jeffy Chen wrote:
> The CPU freqs are not supposed to change before cpufreq policies
> properly registered, meaning that they should be used to calculate the
> initial CPU capacities.
> 
> Doing this helps choosing the best CPU during early boot, especially
> for the initramfs decompressing.
> 
> Signed-off-by: Jeffy Chen <jeffy.chen@...k-chips.com>

[...]

> @@ -146,10 +153,15 @@ bool __init topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu)
>  				return false;
>  			}
>  		}
> -		capacity_scale = max(cpu_capacity, capacity_scale);
>  		raw_capacity[cpu] = cpu_capacity;
>  		pr_debug("cpu_capacity: %pOF cpu_capacity=%u (raw)\n",
>  			cpu_node, raw_capacity[cpu]);
> +
> +		cpu_clk = of_clk_get(cpu_node, 0);
> +		if (!PTR_ERR_OR_ZERO(cpu_clk))
> +			per_cpu(max_freq, cpu) = clk_get_rate(cpu_clk) / 1000;
> +
> +		clk_put(cpu_clk);

I don't like to assume DVFS to be supplied only using 'clk'. So NACK!
We have other non-clk mechanism for CPU DVFS and this needs to simply
use cpufreq APIs to get frequency value if required.

--
Regards,
Sudeep