Re: [PATCH v4 16/37] PM / devfreq: tegra20: Adjust clocks conversion ratio and polling interval

Chanwoo Choi
2020-07-02T01:31:58Z

On 6/9/20 10:13 PM, Dmitry Osipenko wrote:
> The current conversion ratio results in a higher frequency than needed,
> that is not very actual now since the Display Controller driver got
> support for memory bandwidth management and hence memory frequency can
> go lower now without bad consequences. Since memory freq now goes to a
> lower rates, the responsiveness of interactive applications become worse
> due to a quite high polling interval value that is currently set to 500ms.
> Changing polling interval to 30ms results in a good responsiveness of the
> system.
>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
> drivers/devfreq/tegra20-devfreq.c | 14 +++++---------
> 1 file changed, 5 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/devfreq/tegra20-devfreq.c b/drivers/devfreq/tegra20-devfreq.c
> index 249d0dc44f6c..7cdea4ba38f7 100644
> --- a/drivers/devfreq/tegra20-devfreq.c
> +++ b/drivers/devfreq/tegra20-devfreq.c
> @@ -79,16 +79,12 @@ static int tegra_devfreq_get_dev_status(struct device *dev,
>
> /*
> * EMC_COUNT returns number of memory events, that number is lower
> - * than the number of clocks. Conversion ratio of 1/8 results in a
> - * bit higher bandwidth than actually needed, it is good enough for
> - * the time being because drivers don't support requesting minimum
> - * needed memory bandwidth yet.
> - *
> - * TODO: adjust the ratio value once relevant drivers will support
> - * memory bandwidth management.
> + * than the number of total EMC clocks over the sampling period.
> + * The clocks number is converted to maximum possible number of
> + * memory events using the ratio of 1/4.
> */
> stat->busy_time = readl_relaxed(tegra->regs + MC_STAT_EMC_COUNT);
> - stat->total_time = readl_relaxed(tegra->regs + MC_STAT_EMC_CLOCKS) / 8;
> + stat->total_time = readl_relaxed(tegra->regs + MC_STAT_EMC_CLOCKS) / 4;
> stat->current_frequency = clk_get_rate(tegra->emc_clock);
>
> writel_relaxed(EMC_GATHER_CLEAR, tegra->regs + MC_STAT_CONTROL);
> @@ -98,7 +94,7 @@ static int tegra_devfreq_get_dev_status(struct device *dev,
> }
>
> static struct devfreq_dev_profile tegra_devfreq_profile = {
> - .polling_ms = 500,
> + .polling_ms = 30,
> .target = tegra_devfreq_target,
> .get_dev_status = tegra_devfreq_get_dev_status,
> };
>

Ackded-by: Chanwoo Choi <cw00.choi@samsung.com>

--
Best Regards,
Chanwoo Choi
Samsung Electronics