Message-ID: <444ef7e5cf1e6b046a2a7a7d1c152eb0bc3b739c.camel@nxp.com>
Subject: Re: [PATCH v3 3/6] drm: lcdif: Determine bus format and flags in
 ->atomic_check()
From:   Liu Ying <victor.liu@nxp.com>
To:     Alexander Stein <alexander.stein@ew.tq-group.com>,
        dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Cc:     marex@denx.de, stefan@agner.ch, airlied@gmail.com, daniel@ffwll.ch,
        robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org,
        shawnguo@kernel.org, s.hauer@pengutronix.de, kernel@pengutronix.de,
        festevam@gmail.com, linux-imx@nxp.com,
        krzysztof.kozlowski@linaro.org, LW@karo-electronics.de
Date:   Wed, 15 Feb 2023 11:44:15 +0800
In-Reply-To: <1755644.VLH7GnMWUR@steina-w>
References: <20230213085612.1026538-1-victor.liu@nxp.com>
         <20230213085612.1026538-4-victor.liu@nxp.com> <1755644.VLH7GnMWUR@steina-w>
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On Tue, 2023-02-14 at 15:12 +0100, Alexander Stein wrote:
> Hi Liu,

Hi Alexander,

> 
> thanks for the update.

Thanks for your review.

> 
> Am Montag, 13. Februar 2023, 09:56:09 CET schrieb Liu Ying:
> > Instead of determining LCDIF output bus format and bus flags in
> > ->atomic_enable(), do that in ->atomic_check().  This is a
> > preparation for the upcoming patch to check consistent bus format
> > and bus flags across all first downstream bridges in
> > ->atomic_check().
> > New lcdif_crtc_state structure is introduced to cache bus format
> > and bus flags states in ->atomic_check() so that they can be read
> > in ->atomic_enable().
> > 
> > Signed-off-by: Liu Ying <victor.liu@nxp.com>
> > ---
> > v2->v3:
> > * No change.
> > 
> > v1->v2:
> > * Split from patch 2/2 in v1. (Marek, Alexander)
> > * Add comment on the 'base' member of lcdif_crtc_state structure to
> >   note it should always be the first member. (Lothar)
> > 
> >  drivers/gpu/drm/mxsfb/lcdif_kms.c | 138 ++++++++++++++++++++++--
> > ------
> >  1 file changed, 100 insertions(+), 38 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/mxsfb/lcdif_kms.c
> > b/drivers/gpu/drm/mxsfb/lcdif_kms.c index
> > e54200a9fcb9..294cecdf5439 100644
> > --- a/drivers/gpu/drm/mxsfb/lcdif_kms.c
> > +++ b/drivers/gpu/drm/mxsfb/lcdif_kms.c
> > @@ -30,6 +30,18 @@
> >  #include "lcdif_drv.h"
> >  #include "lcdif_regs.h"
> > 
> > +struct lcdif_crtc_state {
> > +	struct drm_crtc_state	base;	/* always be the first 
> 
> member */
> 
> Is it strictly necessary that base is the first member?
> to_lcdif_crtc_state() 
> should be able to handle any position within the struct. I mean it's
> sensible 
> to put it in first place. But the comment somehow bugs me.

The comment was added in v2 to make sure to_lcdif_crtc_state() work ok
when a NULL pointer is handed over to it.  The NULL pointer worries
Lothar a bit as we can see Lothar's comment for v1.

> 
> > +	u32			bus_format;
> > +	u32			bus_flags;
> > +};
> > +
> > +static inline struct lcdif_crtc_state *
> > +to_lcdif_crtc_state(struct drm_crtc_state *s)
> > +{
> > +	return container_of(s, struct lcdif_crtc_state, base);
> > +}
> > +
> >  /*
> > -----------------------------------------------------------------
> > ----------
> > -- * CRTC
> >   */
> > @@ -385,48 +397,72 @@ static void lcdif_reset_block(struct
> > lcdif_drm_private
> > *lcdif) readl(lcdif->base + LCDC_V8_CTRL);
> >  }
> > 
> > -static void lcdif_crtc_mode_set_nofb(struct lcdif_drm_private
> > *lcdif,
> > -				     struct drm_plane_state 
> 
> *plane_state,
> > -				     struct drm_bridge_state 
> 
> *bridge_state,
> > -				     const u32 bus_format)
> > +static void lcdif_crtc_mode_set_nofb(struct drm_crtc_state
> > *crtc_state,
> > +				     struct drm_plane_state 
> 
> *plane_state)
> >  {
> > -	struct drm_device *drm = lcdif->crtc.dev;
> > -	struct drm_display_mode *m = &lcdif->crtc.state->adjusted_mode;
> > -	u32 bus_flags = 0;
> > -
> > -	if (lcdif->bridge->timings)
> > -		bus_flags = lcdif->bridge->timings->input_bus_flags;
> > -	else if (bridge_state)
> > -		bus_flags = bridge_state->input_bus_cfg.flags;
> > +	struct lcdif_crtc_state *lcdif_crtc_state =
> > to_lcdif_crtc_state(crtc_state); +	struct drm_device *drm =
> > crtc_state->crtc->dev;
> > +	struct lcdif_drm_private *lcdif = to_lcdif_drm_private(drm);
> > +	struct drm_display_mode *m = &crtc_state->adjusted_mode;
> > 
> >  	DRM_DEV_DEBUG_DRIVER(drm->dev, "Pixel clock: %dkHz (actual:
> > %dkHz)
> 
> \n",
> >  			     m->crtc_clock,
> >  			     (int)(clk_get_rate(lcdif->clk) / 1000));
> >  	DRM_DEV_DEBUG_DRIVER(drm->dev, "Bridge bus_flags: 0x%08X\n",
> > -			     bus_flags);
> > +			     lcdif_crtc_state->bus_flags);
> >  	DRM_DEV_DEBUG_DRIVER(drm->dev, "Mode flags: 0x%08X\n", m-
> > >flags);
> > 
> >  	/* Mandatory eLCDIF reset as per the Reference Manual */
> >  	lcdif_reset_block(lcdif);
> > 
> > -	lcdif_set_formats(lcdif, plane_state, bus_format);
> > +	lcdif_set_formats(lcdif, plane_state, lcdif_crtc_state-
> > >bus_format);
> > 
> > -	lcdif_set_mode(lcdif, bus_flags);
> > +	lcdif_set_mode(lcdif, lcdif_crtc_state->bus_flags);
> >  }
> > 
> >  static int lcdif_crtc_atomic_check(struct drm_crtc *crtc,
> >  				   struct drm_atomic_state *state)
> >  {
> > +	struct drm_device *drm = crtc->dev;
> > +	struct lcdif_drm_private *lcdif = to_lcdif_drm_private(drm);
> >  	struct drm_crtc_state *crtc_state = 
> 
> drm_atomic_get_new_crtc_state(state,
> >  								
> 
> 	  crtc);
> > +	struct lcdif_crtc_state *lcdif_crtc_state =
> > to_lcdif_crtc_state(crtc_state); bool has_primary = crtc_state-
> > >plane_mask
> > &
> >  			   drm_plane_mask(crtc->primary);
> > +	struct drm_bridge_state *bridge_state;
> > +	struct drm_bridge *bridge = lcdif->bridge;
> > +	int ret;
> > 
> >  	/* The primary plane has to be enabled when the CRTC is active.
> > */
> >  	if (crtc_state->active && !has_primary)
> >  		return -EINVAL;
> > 
> > -	return drm_atomic_add_affected_planes(state, crtc);
> > +	ret = drm_atomic_add_affected_planes(state, crtc);
> > +	if (ret)
> > +		return ret;
> > +
> > +	bridge_state = drm_atomic_get_new_bridge_state(state, bridge);
> > +	if (!bridge_state)
> > +		lcdif_crtc_state->bus_format = MEDIA_BUS_FMT_FIXED;
> > +	else
> > +		lcdif_crtc_state->bus_format = bridge_state-
> > input_bus_cfg.format;
> > +
> > +	if (lcdif_crtc_state->bus_format == MEDIA_BUS_FMT_FIXED) {
> > +		dev_warn_once(drm->dev,
> > +			      "Bridge does not provide bus format, 
> 
> assuming
> > MEDIA_BUS_FMT_RGB888_1X24.\n" +			      "Please
> > fix 
> 
> bridge driver by
> > handling atomic_get_input_bus_fmts.\n"); +		lcdif_crtc_stat
> > e-
> > bus_format =
> > MEDIA_BUS_FMT_RGB888_1X24;
> > +	}
> > +
> > +	if (bridge->timings)
> > +		lcdif_crtc_state->bus_flags = bridge->timings-
> > input_bus_flags;
> > +	else if (bridge_state)
> > +		lcdif_crtc_state->bus_flags = bridge_state-
> > input_bus_cfg.flags;
> > +	else
> > +		lcdif_crtc_state->bus_flags = 0;
> > +
> > +	return 0;
> >  }
> > 
> >  static void lcdif_crtc_atomic_flush(struct drm_crtc *crtc,
> > @@ -458,35 +494,21 @@ static void lcdif_crtc_atomic_enable(struct
> > drm_crtc
> > *crtc, struct drm_atomic_state *state)
> >  {
> >  	struct lcdif_drm_private *lcdif = to_lcdif_drm_private(crtc-
> > >dev);
> > -	struct drm_plane_state *new_pstate = 
> 
> drm_atomic_get_new_plane_state(state,
> > -								
> 
> 	    crtc->primary);
> > +	struct drm_crtc_state *new_crtc_state =
> > drm_atomic_get_new_crtc_state(state, crtc); +	struct
> > drm_plane_state
> > *new_plane_state = drm_atomic_get_new_plane_state(state, +		
> > 	
> 
> 							
> > crtc->primary);
> 
> While the rename to 'new_plane_state' makes sense, this is an
> unrelated 
> change.

I'll use 'new_pstate' and 'new_cstate' in next version. 

> 
> >  	struct drm_display_mode *m = &lcdif->crtc.state->adjusted_mode;
> > -	struct drm_bridge_state *bridge_state = NULL;
> >  	struct drm_device *drm = lcdif->drm;
> > -	u32 bus_format;
> >  	dma_addr_t paddr;
> > 
> > -	bridge_state = drm_atomic_get_new_bridge_state(state, lcdif-
> > bridge);
> > -	if (!bridge_state)
> > -		bus_format = MEDIA_BUS_FMT_FIXED;
> > -	else
> > -		bus_format = bridge_state->input_bus_cfg.format;
> > -
> > -	if (bus_format == MEDIA_BUS_FMT_FIXED) {
> > -		dev_warn_once(drm->dev,
> > -			      "Bridge does not provide bus format, 
> 
> assuming
> > MEDIA_BUS_FMT_RGB888_1X24.\n" -			      "Please
> > fix 
> 
> bridge driver by
> > handling atomic_get_input_bus_fmts.\n"); -		bus_format =
> > MEDIA_BUS_FMT_RGB888_1X24;
> > -	}
> > -
> >  	clk_set_rate(lcdif->clk, m->crtc_clock * 1000);
> > 
> >  	pm_runtime_get_sync(drm->dev);
> > 
> > -	lcdif_crtc_mode_set_nofb(lcdif, new_pstate, bridge_state, 
> 
> bus_format);
> > +	lcdif_crtc_mode_set_nofb(new_crtc_state, new_plane_state);
> > 
> >  	/* Write cur_buf as well to avoid an initial corrupt frame */
> > -	paddr = drm_fb_dma_get_gem_addr(new_pstate->fb, new_pstate, 0);
> > +	paddr = drm_fb_dma_get_gem_addr(new_plane_state->fb, 
> 
> new_plane_state, 0);
> >  	if (paddr) {
> >  		writel(lower_32_bits(paddr),
> >  		       lcdif->base + LCDC_V8_CTRLDESCL_LOW0_4);
> > @@ -520,6 +542,46 @@ static void lcdif_crtc_atomic_disable(struct
> > drm_crtc
> > *crtc, pm_runtime_put_sync(drm->dev);
> >  }
> > 
> > +static void lcdif_crtc_reset(struct drm_crtc *crtc)
> > +{
> > +	struct lcdif_crtc_state *state;
> > +
> > +	if (crtc->state)
> > +		__drm_atomic_helper_crtc_destroy_state(crtc->state);
> > +
> > +	kfree(to_lcdif_crtc_state(crtc->state));
> 
> Shouldn't this be just
> if (crtc->state)
> 	crtc->funcs->atomic_destroy_state(crtc, crtc->state);
> 
> similar to what drm_atomic_helper_crtc_reset is doing? This will
> eventually 
> call lcdif_crtc_atomic_destroy_state().

I think you are right.  But, instead of calling crtc->funcs-
>atomic_destroy_state(), I would call lcdif_crtc_atomic_destroy_state()
directly, which looks simpler to me.

> 
> > +	crtc->state = NULL;
> > +
> > +	state = kzalloc(sizeof(*state), GFP_KERNEL);
> > +	if (state)
> > +		__drm_atomic_helper_crtc_reset(crtc, &state->base);
> 
> Is there a specific reason to not call this helper when
> 'state==NULL'? 

Yes, when 'state==NULL', &state->base would de-reference a NULL
pointer.

> drm_atomic_helper_crtc_reset() does call this even when passing NULL
> for 
> crtc_state.
> 
> > +}
> > +
> > +static struct drm_crtc_state *
> > +lcdif_crtc_atomic_duplicate_state(struct drm_crtc *crtc)
> > +{
> > +	struct lcdif_crtc_state *old = to_lcdif_crtc_state(crtc-
> > >state);
> > +	struct lcdif_crtc_state *new;
> > +
> 
> drm_atomic_helper_crtc_duplicate_state() has a check for
> if (WARN_ON(!crtc->state))
> 	return NULL;
> 
> Maybe it should be added here as well. But then the call to 
> to_lcdif_crtc_state() has to be moved down.

I'll add the check in next version.  But, to_lcdif_crtc_state() doesn't
have to be moved down even if crtc->state is NULL, because 'base' is
the first member of struct lcdif_crtc_state and it's safe.

Regards,
Liu Ying