linux-kernel - Re: [PATCH] drm/stm: ltdc: improve pm

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Date:   Wed, 30 Jun 2021 02:35:05 +0200
From:   Marek Vasut <marex@...x.de>
To:     Raphael GALLAIS-POU - foss <raphael.gallais-pou@...s.st.com>
Cc:     Yannick FERTRE <yannick.fertre@...com>,
        Philippe CORNU <philippe.cornu@...com>,
        Raphael GALLAIS-POU <raphael.gallais-pou@...com>,
        Yannick FERTRE - foss <yannick.fertre@...s.st.com>,
        Philippe CORNU - foss <philippe.cornu@...s.st.com>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre TORGUE - foss <alexandre.torgue@...s.st.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Stephen Boyd <swboyd@...omium.org>
Subject: Re: [PATCH] drm/stm: ltdc: improve pm_runtime to stop clocks

On 6/29/21 1:58 PM, Raphael GALLAIS-POU - foss wrote:

[...]

> +++ b/drivers/gpu/drm/stm/ltdc.c
> @@ -425,10 +425,17 @@ static void ltdc_crtc_atomic_enable(struct drm_crtc *crtc,
>   {
>   	struct ltdc_device *ldev = crtc_to_ltdc(crtc);
>   	struct drm_device *ddev = crtc->dev;
> +	int ret;
>   
>   	DRM_DEBUG_DRIVER("\n");
>   
> -	pm_runtime_get_sync(ddev->dev);
> +	if (!pm_runtime_active(ddev->dev)) {
> +		ret = pm_runtime_get_sync(ddev->dev);

All these if (!pm_runtime_active()) then pm_runtime_get_sync() calls 
look like workaround for some larger issue. Shouldn't the pm_runtime do 
some refcounting on its own , so this shouldn't be needed ?