linux-kernel - Re: [PATCH v4 1/5] drm/mxsfb: Move axi clk enable/disable to crtc enable/disable

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Date:   Wed, 08 Aug 2018 20:57:55 +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 1/5] drm/mxsfb: Move axi clk enable/disable to crtc
 enable/disable

On 08.08.2018 18:08, Leonard Crestez wrote:
> The main axi clk is disabled at the end of mxsfb_crtc_mode_set_nofb and
> immediately reenabled in mxsfb_enable_controller.
> 
> Avoid this by moving the handling of axi clk one level up to
> mxsfb_crtc_enable. Do the same for mxsfb_crtc_disable for simmetry
> 
> This shouldn't have any functional effect.
> 
> Signed-off-by: Leonard Crestez <leonard.crestez@....com>

Thanks, looks good!

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

> ---
>  drivers/gpu/drm/mxsfb/mxsfb_crtc.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> index 0abe77675b76..e4fcbb65b969 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> @@ -127,11 +127,10 @@ static void mxsfb_enable_controller(struct
> mxsfb_drm_private *mxsfb)
>  	u32 reg;
>  
>  	if (mxsfb->clk_disp_axi)
>  		clk_prepare_enable(mxsfb->clk_disp_axi);
>  	clk_prepare_enable(mxsfb->clk);
> -	mxsfb_enable_axi_clk(mxsfb);
>  
>  	/* If it was disabled, re-enable the mode again */
>  	writel(CTRL_DOTCLK_MODE, mxsfb->base + LCDC_CTRL + REG_SET);
>  
>  	/* Enable the SYNC signals first, then the DMA engine */
> @@ -157,12 +156,10 @@ static void mxsfb_disable_controller(struct
> mxsfb_drm_private *mxsfb)
>  
>  	reg = readl(mxsfb->base + LCDC_VDCTRL4);
>  	reg &= ~VDCTRL4_SYNC_SIGNALS_ON;
>  	writel(reg, mxsfb->base + LCDC_VDCTRL4);
>  
> -	mxsfb_disable_axi_clk(mxsfb);
> -
>  	clk_disable_unprepare(mxsfb->clk);
>  	if (mxsfb->clk_disp_axi)
>  		clk_disable_unprepare(mxsfb->clk_disp_axi);
>  }
>  
> @@ -206,11 +203,10 @@ static void mxsfb_crtc_mode_set_nofb(struct
> mxsfb_drm_private *mxsfb)
>  	/*
>  	 * It seems, you can't re-program the controller if it is still
>  	 * running. This may lead to shifted pictures (FIFO issue?), so
>  	 * first stop the controller and drain its FIFOs.
>  	 */
> -	mxsfb_enable_axi_clk(mxsfb);
>  
>  	/* Mandatory eLCDIF reset as per the Reference Manual */
>  	err = mxsfb_reset_block(mxsfb->base);
>  	if (err)
>  		return;
> @@ -267,23 +263,23 @@ static void mxsfb_crtc_mode_set_nofb(struct
> mxsfb_drm_private *mxsfb)
>  	       SET_VERT_WAIT_CNT(m->crtc_vtotal - m->crtc_vsync_start),
>  	       mxsfb->base + LCDC_VDCTRL3);
>  
>  	writel(SET_DOTCLK_H_VALID_DATA_CNT(m->hdisplay),
>  	       mxsfb->base + LCDC_VDCTRL4);
> -
> -	mxsfb_disable_axi_clk(mxsfb);
>  }
>  
>  void mxsfb_crtc_enable(struct mxsfb_drm_private *mxsfb)
>  {
> +	mxsfb_enable_axi_clk(mxsfb);
>  	mxsfb_crtc_mode_set_nofb(mxsfb);
>  	mxsfb_enable_controller(mxsfb);
>  }
>  
>  void mxsfb_crtc_disable(struct mxsfb_drm_private *mxsfb)
>  {
>  	mxsfb_disable_controller(mxsfb);
> +	mxsfb_disable_axi_clk(mxsfb);
>  }
>  
>  void mxsfb_plane_atomic_update(struct mxsfb_drm_private *mxsfb,
>  			       struct drm_plane_state *state)
>  {