linux-kernel - Re: [PATCH 31/39] drm: renesas: shmobile: Turn vblank on/off when enabling/disabling CRTC

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Message-ID: <20230623170921.GI2112@pendragon.ideasonboard.com>
Date:   Fri, 23 Jun 2023 20:09:21 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Magnus Damm <magnus.damm@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 31/39] drm: renesas: shmobile: Turn vblank on/off when
 enabling/disabling CRTC

Hi Geert,

Thank you for the patch.

On Thu, Jun 22, 2023 at 11:21:43AM +0200, Geert Uytterhoeven wrote:
> The DRM core vblank handling mechanism requires drivers to forcefully
> turn vblank reporting off when disabling the CRTC, and to restore the
> vblank reporting status when enabling the CRTC.
> Implement this using the drm_crtc_vblank_{on,off}() helpers.
> 
> Note that drm_crtc_vblank_off() must be called at startup to synchronize
> the state of the vblank core code with the hardware, which is initially
> disabled.  This is performed at CRTC creation time, requiring vertical
> blank initialization to be moved before creating CRTCs.
> 
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>

Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>

> ---
>  drivers/gpu/drm/renesas/shmobile/shmob_drm_crtc.c | 10 +++++++++-
>  drivers/gpu/drm/renesas/shmobile/shmob_drm_drv.c  | 12 ++++++------
>  2 files changed, 15 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/renesas/shmobile/shmob_drm_crtc.c b/drivers/gpu/drm/renesas/shmobile/shmob_drm_crtc.c
> index d2a0ac5f9368c11c..b184019d8b1ed89c 100644
> --- a/drivers/gpu/drm/renesas/shmobile/shmob_drm_crtc.c
> +++ b/drivers/gpu/drm/renesas/shmobile/shmob_drm_crtc.c
> @@ -267,6 +267,9 @@ static void shmob_drm_crtc_start(struct shmob_drm_crtc *scrtc)
>  
>  	shmob_drm_crtc_start_stop(scrtc, true);
>  
> +	/* Turn vertical blank interrupt reporting back on. */
> +	drm_crtc_vblank_on(crtc);
> +
>  	scrtc->started = true;
>  }
>  
> @@ -332,10 +335,12 @@ static void shmob_drm_crtc_stop(struct shmob_drm_crtc *scrtc)
>  		return;
>  
>  	/*
> -	 * Wait for page flip completion before stopping the CRTC as userspace
> +	 * Disable vertical blank interrupt reporting.  We first need to wait
> +	 * for page flip completion before stopping the CRTC as userspace
>  	 * expects page flips to eventually complete.
>  	 */
>  	shmob_drm_crtc_wait_page_flip(scrtc);
> +	drm_crtc_vblank_off(crtc);
>  
>  	/* Stop the LCDC. */
>  	shmob_drm_crtc_start_stop(scrtc, false);
> @@ -571,6 +576,9 @@ int shmob_drm_crtc_create(struct shmob_drm_device *sdev)
>  
>  	drm_crtc_helper_add(crtc, &crtc_helper_funcs);
>  
> +	/* Start with vertical blank interrupt reporting disabled. */
> +	drm_crtc_vblank_off(crtc);
> +
>  	return 0;
>  }
>  
> diff --git a/drivers/gpu/drm/renesas/shmobile/shmob_drm_drv.c b/drivers/gpu/drm/renesas/shmobile/shmob_drm_drv.c
> index 6eaf2c5a104f451a..a29c0c1093725b6e 100644
> --- a/drivers/gpu/drm/renesas/shmobile/shmob_drm_drv.c
> +++ b/drivers/gpu/drm/renesas/shmobile/shmob_drm_drv.c
> @@ -189,17 +189,17 @@ static int shmob_drm_probe(struct platform_device *pdev)
>  	if (ret < 0)
>  		return ret;
>  
> -	ret = shmob_drm_modeset_init(sdev);
> -	if (ret < 0)
> -		return dev_err_probe(&pdev->dev, ret,
> -				     "failed to initialize mode setting\n");
> -
>  	ret = drm_vblank_init(ddev, 1);
>  	if (ret < 0) {
>  		dev_err(&pdev->dev, "failed to initialize vblank\n");
> -		goto err_modeset_cleanup;
> +		return ret;
>  	}
>  
> +	ret = shmob_drm_modeset_init(sdev);
> +	if (ret < 0)
> +		return dev_err_probe(&pdev->dev, ret,
> +				     "failed to initialize mode setting\n");
> +
>  	ret = platform_get_irq(pdev, 0);
>  	if (ret < 0)
>  		goto err_modeset_cleanup;

-- 
Regards,

Laurent Pinchart