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Date:   Wed, 1 Nov 2023 15:54:06 +0200
From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Cc:     Aradhya Bhatia <a-bhatia1@ti.com>,
        Devarsh Thakkar <devarsht@ti.com>,
        Jyri Sarha <jyri.sarha@iki.fi>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 02/10] drm/tidss: Use PM autosuspend
Message-ID: <20231101135406.GR12764@pendragon.ideasonboard.com>
References: <20231101-tidss-probe-v1-0-45149e0f9415@ideasonboard.com>
 <20231101-tidss-probe-v1-2-45149e0f9415@ideasonboard.com>
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In-Reply-To: <20231101-tidss-probe-v1-2-45149e0f9415@ideasonboard.com>
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Hi Tomi,

Thank you for the patch.

On Wed, Nov 01, 2023 at 11:17:39AM +0200, Tomi Valkeinen wrote:
> Use runtime PM autosuspend feature, with 1s timeout, to avoid
> unnecessary suspend-resume cycles when, e.g. the userspace temporarily
> turns off the crtcs when configuring the outputs.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
> ---
>  drivers/gpu/drm/tidss/tidss_drv.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/tidss/tidss_drv.c b/drivers/gpu/drm/tidss/tidss_drv.c
> index f403db11b846..64914331715a 100644
> --- a/drivers/gpu/drm/tidss/tidss_drv.c
> +++ b/drivers/gpu/drm/tidss/tidss_drv.c
> @@ -43,7 +43,9 @@ void tidss_runtime_put(struct tidss_device *tidss)
>  
>  	dev_dbg(tidss->dev, "%s\n", __func__);
>  
> -	r = pm_runtime_put_sync(tidss->dev);
> +	pm_runtime_mark_last_busy(tidss->dev);
> +
> +	r = pm_runtime_put_autosuspend(tidss->dev);
>  	WARN_ON(r < 0);
>  }
>  
> @@ -144,6 +146,9 @@ static int tidss_probe(struct platform_device *pdev)
>  
>  	pm_runtime_enable(dev);
>  
> +	pm_runtime_set_autosuspend_delay(dev, 1000);
> +	pm_runtime_use_autosuspend(dev);
> +
>  #ifndef CONFIG_PM
>  	/* If we don't have PM, we need to call resume manually */
>  	dispc_runtime_resume(tidss->dispc);

By the way, there's a way to handle this without any ifdef:

	dispc_runtime_resume(tidss->dispc);

	pm_runtime_set_active(dev);
	pm_runtime_get_noresume(dev);
	pm_runtime_enable(dev);
	pm_runtime_set_autosuspend_delay(dev, 1000);
	pm_runtime_use_autosuspend(dev);

Then, in the error path,

	pm_runtime_dont_use_autosuspend(dev);
	pm_runtime_disable(dev);
	pm_runtime_put_noidle(dev);

	dispc_runtime_suspend(tidss->dispc);

And in remove:

	pm_runtime_dont_use_autosuspend(dev);
	pm_runtime_disable(dev);
	if (!pm_runtime_status_suspended(dev))
		dispc_runtime_suspend(tidss->dispc);
	pm_runtime_set_suspended(dev);

And yes, runtime PM is a horrible API.

> @@ -215,6 +220,7 @@ static void tidss_remove(struct platform_device *pdev)
>  	/* If we don't have PM, we need to call suspend manually */
>  	dispc_runtime_suspend(tidss->dispc);
>  #endif
> +	pm_runtime_dont_use_autosuspend(dev);

This also needs to be done in the probe error path.

>  	pm_runtime_disable(dev);
>  
>  	/* devm allocated dispc goes away with the dev so mark it NULL */
> 

-- 
Regards,

Laurent Pinchart