linux-kernel - Re: [PATCH v6 2/5] drm/panthor: record current and maximum device clock frequencies

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Message-ID: <20240913161407.0a30b68f@collabora.com>
Date: Fri, 13 Sep 2024 16:14:07 +0200
From: Boris Brezillon <boris.brezillon@...labora.com>
To: Adrián Larumbe <adrian.larumbe@...labora.com>
Cc: Steven Price <steven.price@....com>, Liviu Dudau <liviu.dudau@....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>, Sumit Semwal
 <sumit.semwal@...aro.org>, Christian König
 <christian.koenig@....com>, kernel@...labora.com,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH v6 2/5] drm/panthor: record current and maximum device
 clock frequencies

On Fri, 13 Sep 2024 13:42:10 +0100
Adrián Larumbe <adrian.larumbe@...labora.com> wrote:

> In order to support UM in calculating rates of GPU utilisation, the current
> operating and maximum GPU clock frequencies must be recorded during device
> initialisation, and also during OPP state transitions.
> 
> Signed-off-by: Adrián Larumbe <adrian.larumbe@...labora.com>

Reviewed-by: Boris Brezillon <boris.brezillon@...labora.com>

> ---
>  drivers/gpu/drm/panthor/panthor_devfreq.c | 18 +++++++++++++++++-
>  drivers/gpu/drm/panthor/panthor_device.h  |  6 ++++++
>  2 files changed, 23 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_devfreq.c b/drivers/gpu/drm/panthor/panthor_devfreq.c
> index c6d3c327cc24..9d0f891b9b53 100644
> --- a/drivers/gpu/drm/panthor/panthor_devfreq.c
> +++ b/drivers/gpu/drm/panthor/panthor_devfreq.c
> @@ -62,14 +62,20 @@ static void panthor_devfreq_update_utilization(struct panthor_devfreq *pdevfreq)
>  static int panthor_devfreq_target(struct device *dev, unsigned long *freq,
>  				  u32 flags)
>  {
> +	struct panthor_device *ptdev = dev_get_drvdata(dev);
>  	struct dev_pm_opp *opp;
> +	int err;
>  
>  	opp = devfreq_recommended_opp(dev, freq, flags);
>  	if (IS_ERR(opp))
>  		return PTR_ERR(opp);
>  	dev_pm_opp_put(opp);
>  
> -	return dev_pm_opp_set_rate(dev, *freq);
> +	err = dev_pm_opp_set_rate(dev, *freq);
> +	if (!err)
> +		ptdev->current_frequency = *freq;
> +
> +	return err;
>  }
>  
>  static void panthor_devfreq_reset(struct panthor_devfreq *pdevfreq)
> @@ -130,6 +136,7 @@ int panthor_devfreq_init(struct panthor_device *ptdev)
>  	struct panthor_devfreq *pdevfreq;
>  	struct dev_pm_opp *opp;
>  	unsigned long cur_freq;
> +	unsigned long freq = ULONG_MAX;
>  	int ret;
>  
>  	pdevfreq = drmm_kzalloc(&ptdev->base, sizeof(*ptdev->devfreq), GFP_KERNEL);
> @@ -161,6 +168,7 @@ int panthor_devfreq_init(struct panthor_device *ptdev)
>  		return PTR_ERR(opp);
>  
>  	panthor_devfreq_profile.initial_freq = cur_freq;
> +	ptdev->current_frequency = cur_freq;
>  
>  	/* Regulator coupling only takes care of synchronizing/balancing voltage
>  	 * updates, but the coupled regulator needs to be enabled manually.
> @@ -204,6 +212,14 @@ int panthor_devfreq_init(struct panthor_device *ptdev)
>  
>  	dev_pm_opp_put(opp);
>  
> +	/* Find the fastest defined rate  */
> +	opp = dev_pm_opp_find_freq_floor(dev, &freq);
> +	if (IS_ERR(opp))
> +		return PTR_ERR(opp);
> +	ptdev->fast_rate = freq;
> +
> +	dev_pm_opp_put(opp);
> +
>  	/*
>  	 * Setup default thresholds for the simple_ondemand governor.
>  	 * The values are chosen based on experiments.
> diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
> index a48e30d0af30..2109905813e8 100644
> --- a/drivers/gpu/drm/panthor/panthor_device.h
> +++ b/drivers/gpu/drm/panthor/panthor_device.h
> @@ -184,6 +184,12 @@ struct panthor_device {
>  
>  	/** @profile_mask: User-set profiling flags for job accounting. */
>  	u32 profile_mask;
> +
> +	/** @current_frequency: Device clock frequency at present. Set by DVFS*/
> +	unsigned long current_frequency;
> +
> +	/** @fast_rate: Maximum device clock frequency. Set by DVFS */
> +	unsigned long fast_rate;
>  };
>  
>  /**