linux-kernel - Re: [PATCH v2 02/14] regulator: core: Detach coupled regulator before coupling count is dropped

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Message-ID: <b5329801-ef0b-0c8d-aced-75c44f076f29@gmail.com>
Date:   Mon, 24 May 2021 13:20:44 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Nikola Milosavljević <mnidza@...look.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Peter Geis <pgwipeout@...il.com>,
        Nicolas Chauvet <kwizart@...il.com>,
        Viresh Kumar <vireshk@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Matt Merhar <mattmerhar@...tonmail.com>,
        Paul Fertser <fercerpav@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Mikko Perttunen <mperttunen@...dia.com>
Cc:     linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org,
        devicetree@...r.kernel.org, linux-pm@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>,
        linux-clk@...r.kernel.org
Subject: Re: [PATCH v2 02/14] regulator: core: Detach coupled regulator before
 coupling count is dropped

24.05.2021 02:13, Dmitry Osipenko пишет:
> Detach coupled regulator before dropping coupling count in order to allow
> detaching callback to balance voltage of regulators. This is needed by
> NVIDIA Tegra regulator couplers in order to bring back voltage to a value
> that is safe for reboot once regulators are decoupled.
> 
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/regulator/core.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
> index aae978c0c148..83571f83af04 100644
> --- a/drivers/regulator/core.c
> +++ b/drivers/regulator/core.c
> @@ -5084,6 +5084,13 @@ static void regulator_remove_coupling(struct regulator_dev *rdev)
>  
>  	n_coupled = c_desc->n_coupled;
>  
> +	if (coupler && coupler->detach_regulator) {
> +		err = coupler->detach_regulator(coupler, rdev);
> +		if (err)
> +			rdev_err(rdev, "failed to detach from coupler: %pe\n",
> +				 ERR_PTR(err));
> +	}
> +
>  	for (i = 1; i < n_coupled; i++) {
>  		c_rdev = c_desc->coupled_rdevs[i];
>  
> @@ -5111,13 +5118,6 @@ static void regulator_remove_coupling(struct regulator_dev *rdev)
>  		c_desc->n_resolved--;
>  	}
>  
> -	if (coupler && coupler->detach_regulator) {
> -		err = coupler->detach_regulator(coupler, rdev);
> -		if (err)
> -			rdev_err(rdev, "failed to detach from coupler: %pe\n",
> -				 ERR_PTR(err));
> -	}
> -
>  	kfree(rdev->coupling_desc.coupled_rdevs);
>  	rdev->coupling_desc.coupled_rdevs = NULL;
>  }
> 

I now realized that this is a bit too fragile approach. I'll drop this
patch in v3, there are better options of how to manage balancing on
detaching and this is not critical feature for now anyways.