linux-kernel - Re: [PATCH v5 12/36] PM / devfreq: tegra20: Use MC timings for building OPP table

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Date:   Fri, 14 Aug 2020 10:00:45 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Georgi Djakov <georgi.djakov@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Mikko Perttunen <cyndis@...si.fi>
Cc:     linux-tegra@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v5 12/36] PM / devfreq: tegra20: Use MC timings for
 building OPP table

Hi Dmitry,

On 8/14/20 9:05 AM, Dmitry Osipenko wrote:
> The clk_round_rate() won't be usable for building OPP table once
> interconnect support will be added to the EMC driver because that CLK API
> function limits the rounded rate based on the clk rate that is imposed by
> active clk-users, and thus, the rounding won't work as expected if
> interconnect will set the minimum EMC clock rate before devfreq driver is
> loaded. The struct tegra_mc contains memory timings which could be used by
> the devfreq driver for building up OPP table instead of rounding clock
> rate, this patch implements this idea.
> 
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/devfreq/tegra20-devfreq.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/devfreq/tegra20-devfreq.c b/drivers/devfreq/tegra20-devfreq.c
> index 6469dc69c5e0..a985f24098f5 100644
> --- a/drivers/devfreq/tegra20-devfreq.c
> +++ b/drivers/devfreq/tegra20-devfreq.c
> @@ -123,8 +123,7 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
>  {
>  	struct tegra_devfreq *tegra;
>  	struct tegra_mc *mc;
> -	unsigned long max_rate;
> -	unsigned long rate;
> +	unsigned int i;
>  	int err;
>  
>  	mc = tegra_get_memory_controller();
> @@ -135,6 +134,11 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
>  		return err;
>  	}
>  
> +	if (!mc->num_timings) {
> +		dev_info(&pdev->dev, "memory controller has no timings\n");
> +		return -ENODEV;
> +	}
> +
>  	tegra = devm_kzalloc(&pdev->dev, sizeof(*tegra), GFP_KERNEL);
>  	if (!tegra)
>  		return -ENOMEM;
> @@ -151,12 +155,8 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
>  
>  	tegra->regs = mc->regs;
>  
> -	max_rate = clk_round_rate(tegra->emc_clock, ULONG_MAX);
> -
> -	for (rate = 0; rate <= max_rate; rate++) {
> -		rate = clk_round_rate(tegra->emc_clock, rate);
> -
> -		err = dev_pm_opp_add(&pdev->dev, rate, 0);
> +	for (i = 0; i < mc->num_timings; i++) {
> +		err = dev_pm_opp_add(&pdev->dev, mc->timings[i].rate, 0);
>  		if (err) {
>  			dev_err(&pdev->dev, "failed to add opp: %d\n", err);
>  			goto remove_opps;
> 

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

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics