linux-kernel - Re: [PATCH v5 5/7] drm/panthor: call into devfreq for current frequency

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Message-ID: <CAPaKu7S6_0G4rbRP_nCF0Aw9uy1K8ABqi2z8isvpHcVWkWjJaQ@mail.gmail.com>
Date: Fri, 3 Oct 2025 11:18:45 -0700
From: Chia-I Wu <olvaffe@...il.com>
To: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
	Boris Brezillon <boris.brezillon@...labora.com>, Jassi Brar <jassisinghbrar@...il.com>, 
	Chen-Yu Tsai <wenst@...omium.org>, 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>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Matthias Brugger <matthias.bgg@...il.com>, Kees Cook <kees@...nel.org>, 
	"Gustavo A. R. Silva" <gustavoars@...nel.org>, Ulf Hansson <ulf.hansson@...aro.org>, kernel@...labora.com, 
	dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-mediatek@...ts.infradead.org, linux-hardening@...r.kernel.org, 
	linux-pm@...r.kernel.org
Subject: Re: [PATCH v5 5/7] drm/panthor: call into devfreq for current frequency

On Mon, Sep 29, 2025 at 12:48 AM Nicolas Frattaroli
<nicolas.frattaroli@...labora.com> wrote:
>
> As it stands, panthor keeps a cached current frequency value for when it
> wants to retrieve it. This doesn't work well for when things might
> switch frequency without panthor's knowledge.
>
> Instead, implement the get_cur_freq operation, and expose it through a
> helper function to the rest of panthor.
>
> Reviewed-by: Steven Price <steven.price@....com>
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
> ---
>  drivers/gpu/drm/panthor/panthor_devfreq.c | 33 +++++++++++++++++++++++++++----
>  drivers/gpu/drm/panthor/panthor_devfreq.h |  2 ++
>  drivers/gpu/drm/panthor/panthor_device.h  |  3 ---
>  drivers/gpu/drm/panthor/panthor_drv.c     |  4 +++-
>  4 files changed, 34 insertions(+), 8 deletions(-)
>
[...]
> +
> +unsigned long panthor_devfreq_get_freq(struct panthor_device *ptdev)
> +{
> +       struct panthor_devfreq *pdevfreq = ptdev->devfreq;
> +       unsigned long freq = 0;
> +       int ret;
> +
> +       if (!pdevfreq || !pdevfreq->devfreq)
> +               return 0;
> +
> +       if (pdevfreq->devfreq->profile->get_cur_freq) {
This and the other two NULL checks above seem unnecessary. But let's
follow other functions and check for pdevfreq->devfreq only.

With that, Reviewed-by: Chia-I Wu <olvaffe@...il.com>
> +               ret = pdevfreq->devfreq->profile->get_cur_freq(ptdev->base.dev,
> +                                                              &freq);
> +               if (ret)
> +                       return 0;
> +       }
> +
> +       return freq;
> +}
> diff --git a/drivers/gpu/drm/panthor/panthor_devfreq.h b/drivers/gpu/drm/panthor/panthor_devfreq.h
> index b7631de695f7d79456478c87e8af5dc47673cd1d..f8e29e02f66cb3281ed4bb4c75cda9bd4df82b92 100644
> --- a/drivers/gpu/drm/panthor/panthor_devfreq.h
> +++ b/drivers/gpu/drm/panthor/panthor_devfreq.h
> @@ -18,4 +18,6 @@ void panthor_devfreq_suspend(struct panthor_device *ptdev);
>  void panthor_devfreq_record_busy(struct panthor_device *ptdev);
>  void panthor_devfreq_record_idle(struct panthor_device *ptdev);
>
> +unsigned long panthor_devfreq_get_freq(struct panthor_device *ptdev);
> +
>  #endif /* __PANTHOR_DEVFREQ_H__ */
> diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
> index 9f0649ecfc4fc697a21a8b2fc4dd89c8ecf298df..f32c1868bf6d782d99df9dbd0babcea049c917e0 100644
> --- a/drivers/gpu/drm/panthor/panthor_device.h
> +++ b/drivers/gpu/drm/panthor/panthor_device.h
> @@ -214,9 +214,6 @@ 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;
>
> diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
> index ea4a37b566a8b215f2b7a09c333a696f1dcdb58f..4d59d94c353c3ca76f4b98a411c8f8284efafd08 100644
> --- a/drivers/gpu/drm/panthor/panthor_drv.c
> +++ b/drivers/gpu/drm/panthor/panthor_drv.c
> @@ -25,6 +25,7 @@
>  #include <drm/gpu_scheduler.h>
>  #include <drm/panthor_drm.h>
>
> +#include "panthor_devfreq.h"
>  #include "panthor_device.h"
>  #include "panthor_fw.h"
>  #include "panthor_gem.h"
> @@ -1519,7 +1520,8 @@ static void panthor_gpu_show_fdinfo(struct panthor_device *ptdev,
>                 drm_printf(p, "drm-cycles-panthor:\t%llu\n", pfile->stats.cycles);
>
>         drm_printf(p, "drm-maxfreq-panthor:\t%lu Hz\n", ptdev->fast_rate);
> -       drm_printf(p, "drm-curfreq-panthor:\t%lu Hz\n", ptdev->current_frequency);
> +       drm_printf(p, "drm-curfreq-panthor:\t%lu Hz\n",
> +                  panthor_devfreq_get_freq(ptdev));
>  }
>
>  static void panthor_show_internal_memory_stats(struct drm_printer *p, struct drm_file *file)
>
> --
> 2.51.0
>