linux-kernel - Re: [PATCH v4 17/19] thermal/tegra: Do not enable the thermal zone, it is already enabled

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Date:   Wed, 1 Mar 2023 15:29:56 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     rafael@...nel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>,
        "open list:TEGRA ARCHITECTURE SUPPORT" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH v4 17/19] thermal/tegra: Do not enable the thermal zone,
 it is already enabled

On Tue, Feb 28, 2023 at 12:22:36PM +0100, Daniel Lezcano wrote:
> The code enables the thermal zone after setting it up. But the thermal
> zone is already enabled by thermal_of_zone_register() function.
> 
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> ---
>  drivers/thermal/tegra/tegra30-tsensor.c | 8 +-------
>  1 file changed, 1 insertion(+), 7 deletions(-)
> 
> diff --git a/drivers/thermal/tegra/tegra30-tsensor.c b/drivers/thermal/tegra/tegra30-tsensor.c
> index 3506c3f3c474..e38902abf207 100644
> --- a/drivers/thermal/tegra/tegra30-tsensor.c
> +++ b/drivers/thermal/tegra/tegra30-tsensor.c
> @@ -346,7 +346,7 @@ static int tegra_tsensor_enable_hw_channel(const struct tegra_tsensor *ts,
>  {
>  	const struct tegra_tsensor_channel *tsc = &ts->ch[id];
>  	struct thermal_zone_device *tzd = tsc->tzd;
> -	int err, hot_trip = 0, crit_trip = 0;
> +	int hot_trip = 0, crit_trip = 0;
>  	u32 val;
>  
>  	if (!tzd) {
> @@ -401,12 +401,6 @@ static int tegra_tsensor_enable_hw_channel(const struct tegra_tsensor *ts,
>  	val |= FIELD_PREP(TSENSOR_SENSOR0_CONFIG0_INTR_THERMAL_RST_EN, 1);
>  	writel_relaxed(val, tsc->regs + TSENSOR_SENSOR0_CONFIG0);
>  
> -	err = thermal_zone_device_enable(tzd);
> -	if (err) {
> -		dev_err(ts->dev, "ch%u: failed to enable zone: %d\n", id, err);
> -		return err;
> -	}
> -
>  	return 0;
>  }

This function is called in tegra_tsensor_resume() and balances out the
tegra_tsensor_hw_channel() calls from tegra_tsensor_suspend(). If we
remove the call from here, we'll likely end up with the zones disabled
after a resume.

This ends up calling thermal_zone_device_set_mode(), which is a no-op,
basically, if the mode is unchanged, so this seems harmless.

If you need this to change anyway, I suppose we could move the calls to
thermal_zone_device_enable() and move them into suspend/resume instead.
That's a bit tricky to undo in the error recovery paths, but should be
doable.

Thierry

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