linux-kernel - Re: [PATCH v2 1/2] drm/panfrost: Add missing OPP table refcnt decremental

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Message-ID: <20241003165638.65a2d16e@collabora.com>
Date: Thu, 3 Oct 2024 16:56:38 +0200
From: Boris Brezillon <boris.brezillon@...labora.com>
To: Adrián Larumbe <adrian.larumbe@...labora.com>
Cc: Rob Herring <robh@...nel.org>, Steven Price <steven.price@....com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
 <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David Airlie
 <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, AngeloGioacchino Del
 Regno <angelogioacchino.delregno@...labora.com>, kernel@...labora.com,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] drm/panfrost: Add missing OPP table refcnt
 decremental

On Thu,  3 Oct 2024 14:30:28 +0100
Adrián Larumbe <adrian.larumbe@...labora.com> wrote:

> Commit f11b0417eec2 ("drm/panfrost: Add fdinfo support GPU load metrics")
> retrieves the OPP for the maximum device clock frequency, but forgets to
> keep the reference count balanced by putting the returned OPP object. This
> eventually leads to an OPP core warning when removing the device.
> 
> Fix it by putting OPP objects as many times as they're retrieved. That
> includes putting the OPP object in case setting it fails.
> 
> Also remove an unnecessary whitespace.
> 
> Signed-off-by: Adrián Larumbe <adrian.larumbe@...labora.com>
> Fixes: f11b0417eec2 ("drm/panfrost: Add fdinfo support GPU load metrics")
> ---
>  drivers/gpu/drm/panfrost/panfrost_devfreq.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> index 2d30da38c2c3..4b8840a41779 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> @@ -38,7 +38,7 @@ static int panfrost_devfreq_target(struct device *dev, unsigned long *freq,
>  		return PTR_ERR(opp);
>  	dev_pm_opp_put(opp);
>  
> -	err =  dev_pm_opp_set_rate(dev, *freq);
> +	err = dev_pm_opp_set_rate(dev, *freq);
>  	if (!err)
>  		ptdev->pfdevfreq.current_frequency = *freq;
>  
> @@ -184,9 +184,12 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
>  	ret = dev_pm_opp_set_opp(dev, opp);

Put the dev_pm_opp_put(opp) here, and you can drop the one in the error
path.

>  	if (ret) {
>  		DRM_DEV_ERROR(dev, "Couldn't set recommended OPP\n");
> +		dev_pm_opp_put(opp);
>  		return ret;
>  	}
>  
> +	dev_pm_opp_put(opp);
> +
>  	/* Find the fastest defined rate  */
>  	opp = dev_pm_opp_find_freq_floor(dev, &freq);
>  	if (IS_ERR(opp))