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

MyungJoo Ham
2015-03-18T05:24:00Z

> 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 <tomeu.vizoso@collabora.com>
> ---
> drivers/devfreq/tegra-devfreq.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/devfreq/tegra-devfreq.c b/drivers/devfreq/tegra-devfreq.c
> index 5a6164c..1de3f8b 100644
> --- a/drivers/devfreq/tegra-devfreq.c
> +++ b/drivers/devfreq/tegra-devfreq.c
> @@ -618,6 +618,7 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
> struct tegra_devfreq_device *dev;
> struct resource *res;
> unsigned int i;
> + unsigned long rate;
> int irq;
> int err;
>
> @@ -649,12 +650,6 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
> return PTR_ERR(tegra->emc_clock);
> }
>
> - err = of_init_opp_table(&pdev->dev);
> - if (err) {
> - dev_err(&pdev->dev, "Failed to init operating point table\n");
> - return err;
> - }
> -
> clk_set_rate(tegra->emc_clock, ULONG_MAX);
>
> tegra->rate_change_nb.notifier_call = tegra_actmon_rate_notify_cb;
> @@ -691,6 +686,11 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
> tegra_actmon_configure_device(tegra, dev);
> }
>
> + 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.)

Cheers,
MyungJoo

> irq = platform_get_irq(pdev, 0);
> if (irq <= 0) {
> dev_err(&pdev->dev, "Failed to get IRQ\n");
> --
> 2.1.0
>