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

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Message-ID: <20190912080720.bn7bmu2o3gacrpf4@uno.localdomain>
Date:   Thu, 12 Sep 2019 10:07:20 +0200
From:   Jacopo Mondi <jacopo@...ndi.org>
To:     Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
Cc:     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, 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 Kieran,

On Wed, Sep 11, 2019 at 07:40:27PM +0100, Kieran Bingham wrote:
> 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?

I recall I tested that (that's why I had to add stubs for CMM
functions, as I had linkage errors otherwise) and thing seems to be
fine as the CMM configuration/enblement resolve to an empty function.

Would you prefer to have this guarded by an #if IS_ENABLED() ?

Thanks
   j
>
>
> >  	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
> >   */
> >
>

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