linux-kernel - Re: [PATCH 2/2] drm/panfrost: add devfreq regulator support

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Date:   Mon, 13 Apr 2020 14:18:03 +0100
From:   Steven Price <steven.price@....com>
To:     Clément Péron <peron.clem@...il.com>,
        Rob Herring <robh@...nel.org>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] drm/panfrost: add devfreq regulator support

On 11/04/2020 21:06, Clément Péron wrote:
> OPP table can defined both frequency and voltage.
> 
> Register the mali regulator if it exist.
> 
> Signed-off-by: Clément Péron <peron.clem@...il.com>
> ---
>   drivers/gpu/drm/panfrost/panfrost_devfreq.c | 34 ++++++++++++++++++---
>   drivers/gpu/drm/panfrost/panfrost_device.h  |  1 +
>   2 files changed, 31 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> index 62541f4edd81..2dc8e2355358 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> @@ -78,12 +78,26 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
>   	struct device *dev = &pfdev->pdev->dev;
>   	struct devfreq *devfreq;
>   	struct thermal_cooling_device *cooling;
> +	const char *mali = "mali";
> +	struct opp_table *opp_table = NULL;
> +
> +	/* Regulator is optional */
> +	opp_table = dev_pm_opp_set_regulators(dev, &mali, 1);

This looks like it applies before 3e1399bccf51 ("drm/panfrost: Add 
support for multiple regulators") which is currently in drm-misc-next 
(and linux-next). You want something more like:

     opp_table = dev_pm_opp_set_regulators(dev,
                                           pfdev->comp->supply_names,
                                           pfdev->comp->num_supplies);

Otherwise a platform with multiple regulators won't work correctly.

Also running on my firefly (RK3288) board I get the following warning:

    debugfs: Directory 'ffa30000.gpu-mali' with parent 'vdd_gpu' already 
present!

This is due to the regulator debugfs entries getting created twice (once 
in panfrost_regulator_init() and once here).

I have been taking a look at doing the same thing (I picked up Martin 
Blumenstingl's patch series[1]), but haven't had much time to focus on 
this recently.

Thanks,

Steve

[1] 
https://lore.kernel.org/dri-devel/20200112001623.2121227-1-martin.blumenstingl@googlemail.com/


> +	if (IS_ERR(opp_table)) {
> +		ret = PTR_ERR(opp_table);
> +		if (ret != -ENODEV) {
> +			DRM_DEV_ERROR(dev, "Failed to set regulator: %d\n", ret);
> +			return ret;
> +		}
> +	}
> +	pfdev->devfreq.opp_table = opp_table;
>   
>   	ret = dev_pm_opp_of_add_table(dev);
> -	if (ret == -ENODEV) /* Optional, continue without devfreq */
> -		return 0;
> -	else if (ret)
> -		return ret;
> +	if (ret) {
> +		if (ret == -ENODEV) /* Optional, continue without devfreq */
> +			ret = 0;
> +		goto err_opp_reg;
> +	}
>   
>   	panfrost_devfreq_reset(pfdev);
>   
> @@ -119,6 +133,12 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
>   err_opp:
>   	dev_pm_opp_of_remove_table(dev);
>   
> +err_opp_reg:
> +	if (pfdev->devfreq.opp_table) {
> +		dev_pm_opp_put_regulators(pfdev->devfreq.opp_table);
> +		pfdev->devfreq.opp_table = NULL;
> +	}
> +
>   	return ret;
>   }
>   
> @@ -126,7 +146,13 @@ void panfrost_devfreq_fini(struct panfrost_device *pfdev)
>   {
>   	if (pfdev->devfreq.cooling)
>   		devfreq_cooling_unregister(pfdev->devfreq.cooling);
> +
>   	dev_pm_opp_of_remove_table(&pfdev->pdev->dev);
> +
> +	if (pfdev->devfreq.opp_table) {
> +		dev_pm_opp_put_regulators(pfdev->devfreq.opp_table);
> +		pfdev->devfreq.opp_table = NULL;
> +	}
>   }
>   
>   void panfrost_devfreq_resume(struct panfrost_device *pfdev)
> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
> index 06713811b92c..f6b0c779dfe5 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.h
> @@ -86,6 +86,7 @@ struct panfrost_device {
>   	struct {
>   		struct devfreq *devfreq;
>   		struct thermal_cooling_device *cooling;
> +		struct opp_table *opp_table;
>   		ktime_t busy_time;
>   		ktime_t idle_time;
>   		ktime_t time_last_update;
>