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

From: Chanwoo Choi <cw00.choi-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
To: Dmitry Osipenko <digetx-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Thierry Reding
	<thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	MyungJoo Ham
	<myungjoo.ham-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>,
	Kyungmin Park
	<kyungmin.park-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>,
	Jonathan Hunter
	<jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>,
	Michael Turquette
	<mturquette-rdvid1DuHRBWk0Htik3J/w@public.gmane.org>,
	Stephen Boyd <sboyd-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: linux-clk-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-pm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH v1 3/5] PM / devfreq: tegra20: Use clk_round_rate_unboundly()
Date: Wed, 1 Apr 2020 08:22:30 +0900	[thread overview]
Message-ID: <8e62e4ac-081c-a1ac-f0a9-b4e882fcd3b5@samsung.com> (raw)
In-Reply-To: <20200330231617.17079-4-digetx-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>

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-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> ---
>  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-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics