linux-kernel - Re: [PATCH v2 15/48] opp: Support set_opp() customization without requiring to use regulators

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Message-ID: <20201222090139.vopgc2ju72kr4ujy@vireshk-i7>
Date:   Tue, 22 Dec 2020 14:31:39 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Peter Geis <pgwipeout@...il.com>,
        Nicolas Chauvet <kwizart@...il.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Viresh Kumar <vireshk@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-media@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-clk@...r.kernel.org
Subject: Re: [PATCH v2 15/48] opp: Support set_opp() customization without
 requiring to use regulators

On 17-12-20, 21:06, Dmitry Osipenko wrote:
> Support set_opp() customization without requiring to use regulators. This
> is needed by drivers which want to use dev_pm_opp_set_rate() for changing
> rates of a multiple clocks and don't need to touch regulator.
> 
> One example is NVIDIA Tegra30/114 SoCs which have two sibling 3D hardware
> units which should be use to the same clock rate, meanwhile voltage
> scaling is done using a power domain. In this case OPP table doesn't have
> a regulator, causing a NULL dereference in _set_opp_custom().
> 
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/opp/core.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> index 3d02fe33630b..625dae7a5ecb 100644
> --- a/drivers/opp/core.c
> +++ b/drivers/opp/core.c
> @@ -828,17 +828,25 @@ static int _set_opp_custom(const struct opp_table *opp_table,
>  			   struct dev_pm_opp_supply *old_supply,
>  			   struct dev_pm_opp_supply *new_supply)
>  {
> -	struct dev_pm_set_opp_data *data;
> +	struct dev_pm_set_opp_data *data, tmp_data;
> +	unsigned int regulator_count;
>  	int size;
>  
> -	data = opp_table->set_opp_data;
> +	if (opp_table->set_opp_data) {
> +		data = opp_table->set_opp_data;
> +		regulator_count = opp_table->regulator_count;
> +	} else {
> +		data = &tmp_data;
> +		regulator_count = 0;
> +	}
> +
>  	data->regulators = opp_table->regulators;
> -	data->regulator_count = opp_table->regulator_count;
> +	data->regulator_count = regulator_count;
>  	data->clk = opp_table->clk;
>  	data->dev = dev;
>  
>  	data->old_opp.rate = old_freq;
> -	size = sizeof(*old_supply) * opp_table->regulator_count;
> +	size = sizeof(*old_supply) * regulator_count;
>  	if (!old_supply)
>  		memset(data->old_opp.supplies, 0, size);
>  	else

I don't see you making use of this in this patchset. How did you get this to
crash ?

-- 
viresh