Re: Re: [PATCH v6 5/8] PM / devfreq: tegra: remove operating-points

On 18 March 2015 at 06:23, MyungJoo Ham [off-list ref] wrote:

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As the DT bindings don't have an operating-points property any more,
build the OPP table from the frequencies supported by the EMC clock.

Signed-off-by: Tomeu Vizoso <redacted>
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+     for (rate = 0; rate <= tegra->max_freq * KHZ; rate++) {
+             rate = clk_round_rate(tegra->emc_clock, rate);
+             dev_pm_opp_add(&pdev->dev, rate, 0);
+     }
+

Although I am not going to NACK for the single-time performance of a
single device driver for a device that I do not have or fully understand,
please note that you may be wasting several billion cycles unless
your product is running at MHZ/kHZ level.

What is going on with this loop? Do you really have such a virtually-continuous
frequency scaling in your product? (Wow.... but in such a case, I don't think
OPP is appropriate.)

Actually, that loop is expected to only execute as many times as
frequencies are supported by the clock. This is using knowledge of the
clock always rounding up when possible, which I think is fine in this
case.

Ah. ok. you are using "clk_frac_div_round_rate" of
drivers/clk/tegra/clk-divider.c (DIV_ROUND_UP)

Great. Thanks for the clarification.


Cheers,
MyungJoo

Regards,

Tomeu