linux-kernel - Re: [PATCH v4 2/5] drm/mxsfb: Fix initial corrupt frame when activating display

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Date:   Wed, 08 Aug 2018 20:58:10 +0200
From:   Stefan Agner <stefan@...er.ch>
To:     Leonard Crestez <leonard.crestez@....com>
Cc:     Marek Vasut <marex@...x.de>, Shawn Guo <shawnguo@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Robert Chiras <robert.chiras@....com>,
        Fabio Estevam <fabio.estevam@....com>,
        Anson Huang <Anson.Huang@....com>,
        dri-devel@...ts.freedesktop.org,
        Dong Aisheng <aisheng.dong@....com>, linux-imx@....com,
        kernel@...gutronix.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/5] drm/mxsfb: Fix initial corrupt frame when
 activating display

On 08.08.2018 18:08, Leonard Crestez wrote:
> LCDIF will repeatedly display data from CUR_BUF and set CUR_BUF to
> NEXT_BUF when done. Since we are only ever writing to NEXT_BUF the
> display will show an initial corrupt frame.
> 
> Fix by writing the FB paddr to both CUR_BUF and NEXT_BUF when
> activating the CRTC.
> 
> Signed-off-by: Leonard Crestez <leonard.crestez@....com>
> Tested-by: Philipp Zabel <p.zabel@...gutronix.de>

Reviewed-by: Stefan Agner <stefan@...er.ch>

> ---
>  drivers/gpu/drm/mxsfb/mxsfb_crtc.c | 45 +++++++++++++++++++++---------
>  1 file changed, 32 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> index e4fcbb65b969..24b1f0c1432e 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> @@ -191,10 +191,25 @@ static int mxsfb_reset_block(void __iomem *reset_addr)
>  		return ret;
>  
>  	return clear_poll_bit(reset_addr, MODULE_CLKGATE);
>  }
>  
> +static dma_addr_t mxsfb_get_fb_paddr(struct mxsfb_drm_private *mxsfb)
> +{
> +	struct drm_framebuffer *fb = mxsfb->pipe.plane.state->fb;
> +	struct drm_gem_cma_object *gem;
> +
> +	if (!fb)
> +		return 0;
> +
> +	gem = drm_fb_cma_get_gem_obj(fb, 0);
> +	if (!gem)
> +		return 0;
> +
> +	return gem->paddr;
> +}
> +
>  static void mxsfb_crtc_mode_set_nofb(struct mxsfb_drm_private *mxsfb)
>  {
>  	struct drm_display_mode *m = &mxsfb->pipe.crtc.state->adjusted_mode;
>  	const u32 bus_flags = mxsfb->connector.display_info.bus_flags;
>  	u32 vdctrl0, vsync_pulse_len, hsync_pulse_len;
> @@ -267,12 +282,22 @@ static void mxsfb_crtc_mode_set_nofb(struct
> mxsfb_drm_private *mxsfb)
>  	       mxsfb->base + LCDC_VDCTRL4);
>  }
>  
>  void mxsfb_crtc_enable(struct mxsfb_drm_private *mxsfb)
>  {
> +	dma_addr_t paddr;
> +
>  	mxsfb_enable_axi_clk(mxsfb);
>  	mxsfb_crtc_mode_set_nofb(mxsfb);
> +
> +	/* Write cur_buf as well to avoid an initial corrupt frame */
> +	paddr = mxsfb_get_fb_paddr(mxsfb);
> +	if (paddr) {
> +		writel(paddr, mxsfb->base + mxsfb->devdata->cur_buf);
> +		writel(paddr, mxsfb->base + mxsfb->devdata->next_buf);
> +	}
> +
>  	mxsfb_enable_controller(mxsfb);
>  }
>  
>  void mxsfb_crtc_disable(struct mxsfb_drm_private *mxsfb)
>  {
> @@ -283,16 +308,12 @@ void mxsfb_crtc_disable(struct mxsfb_drm_private *mxsfb)
>  void mxsfb_plane_atomic_update(struct mxsfb_drm_private *mxsfb,
>  			       struct drm_plane_state *state)
>  {
>  	struct drm_simple_display_pipe *pipe = &mxsfb->pipe;
>  	struct drm_crtc *crtc = &pipe->crtc;
> -	struct drm_framebuffer *fb = pipe->plane.state->fb;
>  	struct drm_pending_vblank_event *event;
> -	struct drm_gem_cma_object *gem;
> -
> -	if (!crtc)
> -		return;
> +	dma_addr_t paddr;
>  
>  	spin_lock_irq(&crtc->dev->event_lock);
>  	event = crtc->state->event;
>  	if (event) {
>  		crtc->state->event = NULL;
> @@ -303,14 +324,12 @@ void mxsfb_plane_atomic_update(struct
> mxsfb_drm_private *mxsfb,
>  			drm_crtc_send_vblank_event(crtc, event);
>  		}
>  	}
>  	spin_unlock_irq(&crtc->dev->event_lock);
>  
> -	if (!fb)
> -		return;
> -
> -	gem = drm_fb_cma_get_gem_obj(fb, 0);
> -
> -	mxsfb_enable_axi_clk(mxsfb);
> -	writel(gem->paddr, mxsfb->base + mxsfb->devdata->next_buf);
> -	mxsfb_disable_axi_clk(mxsfb);
> +	paddr = mxsfb_get_fb_paddr(mxsfb);
> +	if (paddr) {
> +		mxsfb_enable_axi_clk(mxsfb);
> +		writel(paddr, mxsfb->base + mxsfb->devdata->next_buf);
> +		mxsfb_disable_axi_clk(mxsfb);
> +	}
>  }