linux-kernel - Re: [PATCH] drm/stm: ltdc: update planes at next vblank to avoid partial refresh

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Message-ID: <7ff86999-02e5-ef48-221c-a5e0e61eb2fd@st.com>
Date:   Mon, 1 Apr 2019 09:22:51 +0000
From:   Philippe CORNU <philippe.cornu@...com>
To:     Yannick FERTRE <yannick.fertre@...com>,
        Vincent ABRIOU <vincent.abriou@...com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        "Alexandre TORGUE" <alexandre.torgue@...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>
Subject: Re: [PATCH] drm/stm: ltdc: update planes at next vblank to avoid
 partial refresh

Dear Yannick,
Thank you for your patch, works fine,

Acked-by: Philippe Cornu <philippe.cornu@...com>

Philippe :-)

On 4/1/19 9:24 AM, Yannick Fertré wrote:
> Plane updates must be synchronized on vblank with the shadow register mechanism
> to avoid partial refresh on screen.
> 
> Signed-off-by: Yannick Fertré <yannick.fertre@...com>
> ---
>   drivers/gpu/drm/stm/ltdc.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
> index b1741a9..c2d0800 100644
> --- a/drivers/gpu/drm/stm/ltdc.c
> +++ b/drivers/gpu/drm/stm/ltdc.c
> @@ -426,8 +426,8 @@ static void ltdc_crtc_atomic_enable(struct drm_crtc *crtc,
>   	/* Enable IRQ */
>   	reg_set(ldev->regs, LTDC_IER, IER_RRIE | IER_FUIE | IER_TERRIE);
>   
> -	/* Immediately commit the planes */
> -	reg_set(ldev->regs, LTDC_SRCR, SRCR_IMR);
> +	/* Commit shadow registers = update planes at next vblank */
> +	reg_set(ldev->regs, LTDC_SRCR, SRCR_VBR);
>   
>   	/* Enable LTDC */
>   	reg_set(ldev->regs, LTDC_GCR, GCR_LTDCEN);
>