linux-kernel - Re: [PATCH v1 1/8] PM / devfreq: tegra: Fix kHz to Hz conversion

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Date:   Fri, 12 Apr 2019 19:56:58 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>
Cc:     linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v1 1/8] PM / devfreq: tegra: Fix kHz to Hz conversion

12.04.2019 1:29, Dmitry Osipenko пишет:
> The kHz to Hz is incorrectly converted in a few places in the code,
> this results in a wrong frequency being calculated because devfreq core
> uses OPP frequencies that are given in Hz to clamp the rate, while
> tegra-devfreq gives to the core value in kHz and then it also expects to
> receive value in kHz from the core. In a result memory freq is always set
> to a value which is close to ULONG_MAX because of the bug. Hence the EMC
> frequency is always capped to the maximum and the driver doesn't do
> anything useful. Let's provide OPP with rates in kHz since this eliminates
> few multiplies and divisions in the code. This patch was tested on Tegra30
> and Tegra124 SoC's, EMC frequency scaling works properly now.
> 
> Cc: <stable@...r.kernel.org>
> Tested-by: Steev Klimaszewski <steev@...i.org>
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/devfreq/tegra-devfreq.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/devfreq/tegra-devfreq.c b/drivers/devfreq/tegra-devfreq.c
> index c89ba7b834ff..ec4ff55f5eea 100644
> --- a/drivers/devfreq/tegra-devfreq.c
> +++ b/drivers/devfreq/tegra-devfreq.c
> @@ -394,7 +394,7 @@ static int tegra_actmon_rate_notify_cb(struct notifier_block *nb,
>  
>  	tegra = container_of(nb, struct tegra_devfreq, rate_change_nb);
>  
> -	tegra->cur_freq = data->new_rate / KHZ;
> +	tegra->cur_freq = data->new_rate;

This was a last-minute change and it is incorrect. The cur_freq should be kept in kHz, I'll fix it up in v2 and re-test everything properly once again.