linux-kernel - Re: [PATCH v4 6/9] drm: rcar-du: crtc: Enable and disable CMMs

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Date:   Wed, 11 Sep 2019 19:40:27 +0100
From:   Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
To:     Jacopo Mondi <jacopo+renesas@...ndi.org>,
        laurent.pinchart@...asonboard.com, geert@...ux-m68k.org,
        horms@...ge.net.au, uli+renesas@...nd.eu,
        VenkataRajesh.Kalakodima@...bosch.com
Cc:     airlied@...ux.ie, daniel@...ll.ch, koji.matsuoka.xm@...esas.com,
        muroya@....co.jp, Harsha.ManjulaMallikarjun@...bosch.com,
        linux-renesas-soc@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 6/9] drm: rcar-du: crtc: Enable and disable CMMs

Hi Jacopo,

On 06/09/2019 14:54, Jacopo Mondi wrote:
> Enable/disable the CMM associated with a CRTC at CRTC start and stop
> time and enable the CMM unit through the Display Extensional Functions
> register at group setup time.
> 
> Reviewed-by: Ulrich Hecht <uli+renesas@...nd.eu>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>
> ---
>  drivers/gpu/drm/rcar-du/rcar_du_crtc.c  | 7 +++++++
>  drivers/gpu/drm/rcar-du/rcar_du_group.c | 8 ++++++++
>  drivers/gpu/drm/rcar-du/rcar_du_regs.h  | 5 +++++
>  3 files changed, 20 insertions(+)
> 
> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
> index 23f1d6cc1719..3dac605c3a67 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
> @@ -21,6 +21,7 @@
>  #include <drm/drm_plane_helper.h>
>  #include <drm/drm_vblank.h>
>  
> +#include "rcar_cmm.h"
>  #include "rcar_du_crtc.h"
>  #include "rcar_du_drv.h"
>  #include "rcar_du_encoder.h"
> @@ -619,6 +620,9 @@ static void rcar_du_crtc_stop(struct rcar_du_crtc *rcrtc)
>  	if (rcar_du_has(rcrtc->dev, RCAR_DU_FEATURE_VSP1_SOURCE))
>  		rcar_du_vsp_disable(rcrtc);
>  
> +	if (rcrtc->cmm)
> +		rcar_cmm_disable(rcrtc->cmm);
> +
>  	/*
>  	 * Select switch sync mode. This stops display operation and configures
>  	 * the HSYNC and VSYNC signals as inputs.
> @@ -686,6 +690,9 @@ static void rcar_du_crtc_atomic_enable(struct drm_crtc *crtc,
>  	}
>  
>  	rcar_du_crtc_start(rcrtc);
> +
> +	if (rcrtc->cmm)
> +		rcar_cmm_enable(rcrtc->cmm);
>  }
>  
>  static void rcar_du_crtc_atomic_disable(struct drm_crtc *crtc,
> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_group.c b/drivers/gpu/drm/rcar-du/rcar_du_group.c
> index 9eee47969e77..25d0fc125d7a 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_du_group.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_du_group.c
> @@ -147,6 +147,14 @@ static void rcar_du_group_setup(struct rcar_du_group *rgrp)
>  
>  	rcar_du_group_setup_pins(rgrp);
>  
> +	if (rcar_du_has(rcdu, RCAR_DU_FEATURE_CMM)) {
> +		u32 defr7 = DEFR7_CODE
> +			  | (rgrp->cmms_mask & BIT(1) ? DEFR7_CMME1 : 0)
> +			  | (rgrp->cmms_mask & BIT(0) ? DEFR7_CMME0 : 0);
> +
> +		rcar_du_group_write(rgrp, DEFR7, defr7);
> +	}
> +

What's the effect here on platforms with a CMM, but with
CONFIG_DRM_RCAR_CMM unset?

Will this incorrectly configure the DU ?

Will it stall the display if the DU tries to interact with another
module which is not enabled?


>  	if (rcdu->info->gen >= 2) {
>  		rcar_du_group_setup_defr8(rgrp);
>  		rcar_du_group_setup_didsr(rgrp);
> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_regs.h b/drivers/gpu/drm/rcar-du/rcar_du_regs.h
> index bc87f080b170..fb9964949368 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_du_regs.h
> +++ b/drivers/gpu/drm/rcar-du/rcar_du_regs.h
> @@ -197,6 +197,11 @@
>  #define DEFR6_MLOS1		(1 << 2)
>  #define DEFR6_DEFAULT		(DEFR6_CODE | DEFR6_TCNE1)
>  
> +#define DEFR7			0x000ec
> +#define DEFR7_CODE		(0x7779 << 16)
> +#define DEFR7_CMME1		BIT(6)
> +#define DEFR7_CMME0		BIT(4)
> +
>  /* -----------------------------------------------------------------------------
>   * R8A7790-only Control Registers
>   */
>