Subject: Re: [PATCH v4 13/14] drm/mxsfb: Add support for horizontal stride

From: Laurent Pinchart <[email-masked]>
Date: Wed, 6 Nov 2019 00:12:30 +0200

On Mon, Oct 14, 2019 at 02:40:55PM +0200, Stefan Agner wrote:
> Hi Robert,
> 
> Sorry it took me so long to have a closer look at this patchset.
> 
> I will definitely merge part of it, but this particular patch actually
> breaks i.MX 7. I have vertical stripes on my display with this patch
> applied (using Weston with DRM backend). Not sure why this exactly
> happens, from what I understand this should only affect IP Version 4.

The code tests for ipversion >= 4, which should match the i.MX7.

> Some notes below:
> 
> On 2019-08-29 13:30, Robert Chiras wrote:
> > Besides the eLCDIF block, there is another IP block, used in the past
> > for EPDC panels. Since the iMX.8mq doesn't have an EPDC connector, this
> > block is not documented, but we can use it to do additional operations
> > on the frame buffer.
> 
> Hm, but this block is part of the ELCDIF block, in terms of clock, power
> domain etc?

On i.MX7 the EPDC IP core is present as the SoC has an EPDC output. Can
the EPDC be used to control LCDIF stride on the i.MX7 too ?

> > In this case, we can use the pigeon registers from this IP block in
> > order to do horizontal crop on the frame buffer processed by the eLCDIF
> > block.
> > 
> > Signed-off-by: Robert Chiras <[email-masked]>
> > Tested-by: Guido Günther <[email-masked]>
> > ---
> >  drivers/gpu/drm/mxsfb/mxsfb_crtc.c | 79 ++++++++++++++++++++++++++++++++++++--
> >  drivers/gpu/drm/mxsfb/mxsfb_drv.c  |  1 +
> >  drivers/gpu/drm/mxsfb/mxsfb_regs.h | 16 ++++++++
> >  3 files changed, 92 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> > b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> > index a12f53d..317575e 100644
> > --- a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> > +++ b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> > @@ -15,6 +15,7 @@
> >  
> >  #include <video/videomode.h>
> >  
> > +#include <drm/drm_atomic.h>
> >  #include <drm/drm_atomic_helper.h>
> >  #include <drm/drm_crtc.h>
> >  #include <drm/drm_fb_cma_helper.h>
> > @@ -435,13 +436,66 @@ void mxsfb_crtc_disable(struct mxsfb_drm_private *mxsfb)
> >  	clk_disable_unprepare(mxsfb->clk_axi);
> >  }
> >  
> > +void mxsfb_set_fb_hcrop(struct mxsfb_drm_private *mxsfb, u32 src_w, u32 fb_w)
> > +{
> > +	u32 mask_cnt, htotal, hcount;
> > +	u32 vdctrl2, vdctrl3, vdctrl4, transfer_count;
> > +	u32 pigeon_12_0, pigeon_12_1, pigeon_12_2;
> > +
> > +	if (src_w == fb_w) {
> > +		writel(0x0, mxsfb->base + HW_EPDC_PIGEON_12_0);
> > +		writel(0x0, mxsfb->base + HW_EPDC_PIGEON_12_1);
> > +
> > +		return;
> > +	}
> > +
> > +	transfer_count = readl(mxsfb->base + LCDC_V4_TRANSFER_COUNT);
> > +	hcount = TRANSFER_COUNT_GET_HCOUNT(transfer_count);
> > +
> > +	transfer_count &= ~TRANSFER_COUNT_SET_HCOUNT(0xffff);
> > +	transfer_count |= TRANSFER_COUNT_SET_HCOUNT(fb_w);
> > +	writel(transfer_count, mxsfb->base + LCDC_V4_TRANSFER_COUNT);
> > +
> > +	vdctrl2 = readl(mxsfb->base + LCDC_VDCTRL2);
> > +	htotal  = VDCTRL2_GET_HSYNC_PERIOD(vdctrl2);
> > +	htotal  += fb_w - hcount;
> > +	vdctrl2 &= ~VDCTRL2_SET_HSYNC_PERIOD(0x3ffff);
> > +	vdctrl2 |= VDCTRL2_SET_HSYNC_PERIOD(htotal);
> > +	writel(vdctrl2, mxsfb->base + LCDC_VDCTRL2);
> > +
> > +	vdctrl4 = readl(mxsfb->base + LCDC_VDCTRL4);
> > +	vdctrl4 &= ~SET_DOTCLK_H_VALID_DATA_CNT(0x3ffff);
> > +	vdctrl4 |= SET_DOTCLK_H_VALID_DATA_CNT(fb_w);
> > +	writel(vdctrl4, mxsfb->base + LCDC_VDCTRL4);
> > +
> > +	/* configure related pigeon registers */
> > +	vdctrl3  = readl(mxsfb->base + LCDC_VDCTRL3);
> > +	mask_cnt = GET_HOR_WAIT_CNT(vdctrl3) - 5;
> > +
> > +	pigeon_12_0 = PIGEON_12_0_SET_STATE_MASK(0x24)		|
> > +		      PIGEON_12_0_SET_MASK_CNT(mask_cnt)	|
> > +		      PIGEON_12_0_SET_MASK_CNT_SEL(0x6)		|
> > +		      PIGEON_12_0_POL_ACTIVE_LOW		|
> > +		      PIGEON_12_0_EN;
> > +	writel(pigeon_12_0, mxsfb->base + HW_EPDC_PIGEON_12_0);
> > +
> > +	pigeon_12_1 = PIGEON_12_1_SET_CLR_CNT(src_w) |
> > +		      PIGEON_12_1_SET_SET_CNT(0x0);
> > +	writel(pigeon_12_1, mxsfb->base + HW_EPDC_PIGEON_12_1);
> > +
> > +	pigeon_12_2 = 0x0;
> > +	writel(pigeon_12_2, mxsfb->base + HW_EPDC_PIGEON_12_2);
> > +}
> > +
> >  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_plane_state *new_state = pipe->plane.state;
> > +	struct drm_framebuffer *fb = pipe->plane.state->fb;
> >  	struct drm_pending_vblank_event *event;
> > -	dma_addr_t paddr;
> > +	u32 fb_addr, src_off, src_w, stride, cpp = 0;
> 
> dma_addr_t seems to be the better type here, why change?
> 
> >  
> >  	spin_lock_irq(&crtc->dev->event_lock);
> >  	event = crtc->state->event;
> > @@ -456,10 +510,27 @@ void mxsfb_plane_atomic_update(struct
> > mxsfb_drm_private *mxsfb,
> >  	}
> >  	spin_unlock_irq(&crtc->dev->event_lock);
> >  
> > -	paddr = mxsfb_get_fb_paddr(mxsfb);
> > -	if (paddr) {
> > +	if (!fb)
> > +		return;
> > +
> > +	fb_addr = mxsfb_get_fb_paddr(mxsfb);
> > +	if (mxsfb->devdata->ipversion >= 4) {
> > +		cpp = fb->format->cpp[0];
> > +		src_off = (new_state->src_y >> 16) * fb->pitches[0] +
> > +			  (new_state->src_x >> 16) * cpp;
> > +		fb_addr += fb->offsets[0] + src_off;
> > +	}
> > +
> > +	if (fb_addr) {
> >  		clk_prepare_enable(mxsfb->clk_axi);
> > -		writel(paddr, mxsfb->base + mxsfb->devdata->next_buf);
> > +		writel(fb_addr, mxsfb->base + mxsfb->devdata->next_buf);
> >  		clk_disable_unprepare(mxsfb->clk_axi);
> >  	}
> > +
> > +	if (mxsfb->devdata->ipversion >= 4 &&
> > +	    unlikely(drm_atomic_crtc_needs_modeset(new_state->crtc->state))) {
> > +		stride = DIV_ROUND_UP(fb->pitches[0], cpp);
> > +		src_w = new_state->src_w >> 16;
> > +		mxsfb_set_fb_hcrop(mxsfb, src_w, stride);
> > +	}

I doubt userspace will appreciate the stride being ignored on older
SoCs.

> >  }
> > diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> > b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> > index 888b520..06d3bf0 100644
> > --- a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> > +++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> > @@ -133,6 +133,7 @@ static int mxsfb_atomic_helper_check(struct drm_device *dev,
> >  		if (old_bpp != new_bpp)
> >  			new_state->mode_changed = true;
> >  	}
> > +
> 
> Can you also drop this unrelated change?
> 
> >  	return ret;
> >  }
> >  
> > diff --git a/drivers/gpu/drm/mxsfb/mxsfb_regs.h
> > b/drivers/gpu/drm/mxsfb/mxsfb_regs.h
> > index 0f63ba1..df3279b 100644
> > --- a/drivers/gpu/drm/mxsfb/mxsfb_regs.h
> > +++ b/drivers/gpu/drm/mxsfb/mxsfb_regs.h
> > @@ -145,6 +145,22 @@
> >  #define DEBUG0_HSYNC			BIT(26)
> >  #define DEBUG0_VSYNC			BIT(25)
> >  
> > +/* pigeon registers for crop */
> > +#define HW_EPDC_PIGEON_12_0		0xb00
> > +#define HW_EPDC_PIGEON_12_1		0xb10
> > +#define HW_EPDC_PIGEON_12_2		0xb20
> > +
> > +#define PIGEON_12_0_SET_STATE_MASK(x)	REG_PUT((x), 31, 24)
> > +#define PIGEON_12_0_SET_MASK_CNT(x)	REG_PUT((x), 23, 12)
> > +#define PIGEON_12_0_SET_MASK_CNT_SEL(x)	REG_PUT((x), 11,  8)
> > +#define PIGEON_12_0_SET_OFFSET(x)	REG_PUT((x),  7,  4)
> > +#define PIGEON_12_0_SET_INC_SEL(x)	REG_PUT((x),  3,  2)
> > +#define PIGEON_12_0_POL_ACTIVE_LOW	BIT(1)
> > +#define PIGEON_12_0_EN			BIT(0)
> > +
> > +#define PIGEON_12_1_SET_CLR_CNT(x)	REG_PUT((x), 31, 16)
> > +#define PIGEON_12_1_SET_SET_CNT(x)	REG_PUT((x), 15,  0)
> > +
> >  #define MXSFB_MIN_XRES			120
> >  #define MXSFB_MIN_YRES			120
> >  #define MXSFB_MAX_XRES			0xffff

-- 
Regards,

Laurent Pinchart

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