Re: [PATCH v1 3/5] PM / devfreq: tegra20: Use clk_round_rate_unboundly()

[Chanwoo Choi]

Hi Dmitry,

On 3/31/20 8:16 AM, Dmitry Osipenko wrote:
> The clk_round_rate() doesn't work for us properly if clock rate is bounded
> by a min/max rate that is requested by some other clk-user because we're
> building devfreq's OPP table based on the rounding.
> 
> In particular this becomes a problem if display driver is probed earlier
> than devfreq, and thus, display adds a memory bandwidth request using
> interconnect API, which results in a minimum clock-rate being set for
> the memory clk. In a result, the lowest devfreq OPP rate is getting
> limited to the minimum rate imposed by the display driver.
> 
> Let's use new clk_round_rate_unboundly() that resolves the problem by
> rounding clock rate without taking into account min/max limits imposed by
> active clk users.
> 
> Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
> ---
>  drivers/devfreq/tegra20-devfreq.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/devfreq/tegra20-devfreq.c b/drivers/devfreq/tegra20-devfreq.c
> index ff82bac9ee4e..1bb10ef11dfe 100644
> --- a/drivers/devfreq/tegra20-devfreq.c
> +++ b/drivers/devfreq/tegra20-devfreq.c
> @@ -149,10 +149,10 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
>  
>  	tegra->regs = mc->regs;
>  
> -	max_rate = clk_round_rate(tegra->emc_clock, ULONG_MAX);
> +	max_rate = clk_round_rate_unboundly(tegra->emc_clock, ULONG_MAX);
>  
>  	for (rate = 0; rate <= max_rate; rate++) {
> -		rate = clk_round_rate(tegra->emc_clock, rate);
> +		rate = clk_round_rate_unboundly(tegra->emc_clock, rate);
>  
>  		err = dev_pm_opp_add(&pdev->dev, rate, 0);
>  		if (err) {
> 

Firstly, patch1 have to be reviewed for this patch.
I have no any objection. It looks good to me.

If patch1 get the confirmation from clock maintainer,
feel free to add my acked tag:
Acked-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx>

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics