Re: [RFC PATCH v4 03/12] PM: Introduce an Energy Model management framework

[Peter Zijlstra]

On Thu, Jun 28, 2018 at 12:40:34PM +0100, Quentin Perret wrote:
> +/* fd_update_cs_table() - Computes the capacity values of a cs_table
> + *
> + * This assumes a linear relation between capacity and frequency. As such,
> + * the capacity of a CPU at the n^th capacity state is computed as:
> + *           capactity(n) = max_capacity * freq(n) / freq_max
> + */

Broken comment style

> +static void fd_update_cs_table(struct em_cs_table *cs_table, int cpu)
> +{
> +	unsigned long cmax = arch_scale_cpu_capacity(NULL, cpu);
> +	int max_cap_state = cs_table->nr_cap_states - 1;
> +	unsigned long fmax = cs_table->state[max_cap_state].frequency;
> +	int i;
> +
> +	for (i = 0; i < cs_table->nr_cap_states; i++) {
> +		u64 cap = (u64)cmax * cs_table->state[i].frequency;
> +		do_div(cap, fmax);
> +		cs_table->state[i].capacity = (unsigned long)cap;

I prefer div64_*() over do_div(), the calling convention the latter
always confuses the heck out of me.

So this then becomes something like:

		cs_table->state[i].capacity =
			div64_u64(cmax * cs_table->state[i].frequency, fmax);

> +	}
> +}