[PATCH v4 08/14] drm/mxsfb: Add max-memory-bandwidth property for MXSFB

[Robert Chiras]

Because of stability issues, we may want to limit the maximum bandwidth
required by the MXSFB (eLCDIF) driver.

Signed-off-by: Robert Chiras <robert.chiras at nxp.com>
Tested-by: Guido Günther <agx at sigxcpu.org>
---
 drivers/gpu/drm/mxsfb/mxsfb_drv.c | 48 +++++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/mxsfb/mxsfb_drv.h |  2 ++
 2 files changed, 50 insertions(+)

diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.c b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
index f95ba63..d8686c7 100644
--- a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
+++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
@@ -158,6 +158,49 @@ static const struct drm_mode_config_helper_funcs mxsfb_mode_config_helpers = {
 	.atomic_commit_tail = drm_atomic_helper_commit_tail_rpm,
 };
 
+enum drm_mode_status mxsfb_pipe_mode_valid(struct drm_crtc *crtc,
+					   const struct drm_display_mode *mode)
+{
+	struct drm_simple_display_pipe *pipe =
+		container_of(crtc, struct drm_simple_display_pipe, crtc);
+	struct mxsfb_drm_private *mxsfb = drm_pipe_to_mxsfb_drm_private(pipe);
+	u32 bpp;
+	u64 bw;
+
+	if (!pipe->plane.state->fb)
+		bpp = 32;
+	else
+		bpp = pipe->plane.state->fb->format->depth;
+
+	bw = mode->crtc_clock * 1000;
+	bw = bw * mode->hdisplay * mode->vdisplay * (bpp / 8);
+	bw = div_u64(bw, mode->htotal * mode->vtotal);
+
+	if (mxsfb->max_bw && (bw > mxsfb->max_bw))
+		return MODE_BAD;
+
+	return MODE_OK;
+}
+
+static int mxsfb_pipe_check(struct drm_simple_display_pipe *pipe,
+			    struct drm_plane_state *plane_state,
+			    struct drm_crtc_state *crtc_state)
+{
+	struct drm_framebuffer *fb = plane_state->fb;
+	struct drm_framebuffer *old_fb = pipe->plane.state->fb;
+
+	/* force 'mode_changed' when fb pitches changed, since
+	 * the pitch related registers configuration of LCDIF
+	 * can not be done when LCDIF is running.
+	 */
+	if (old_fb && likely(!crtc_state->mode_changed)) {
+		if (old_fb->pitches[0] != fb->pitches[0])
+			crtc_state->mode_changed = true;
+	}
+
+	return 0;
+}
+
 static void mxsfb_pipe_enable(struct drm_simple_display_pipe *pipe,
 			      struct drm_crtc_state *crtc_state,
 			      struct drm_plane_state *plane_state)
@@ -244,6 +287,8 @@ static void mxsfb_pipe_disable_vblank(struct drm_simple_display_pipe *pipe)
 }
 
 static struct drm_simple_display_pipe_funcs mxsfb_funcs = {
+	.mode_valid	= mxsfb_pipe_mode_valid,
+	.check          = mxsfb_pipe_check,
 	.enable		= mxsfb_pipe_enable,
 	.disable	= mxsfb_pipe_disable,
 	.update		= mxsfb_pipe_update,
@@ -283,6 +328,9 @@ static int mxsfb_load(struct drm_device *drm, unsigned long flags)
 	if (IS_ERR(mxsfb->clk_disp_axi))
 		mxsfb->clk_disp_axi = NULL;
 
+	of_property_read_u32(drm->dev->of_node, "max-memory-bandwidth",
+			     &mxsfb->max_bw);
+
 	ret = dma_set_mask_and_coherent(drm->dev, DMA_BIT_MASK(32));
 	if (ret)
 		return ret;
diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.h b/drivers/gpu/drm/mxsfb/mxsfb_drv.h
index 8fb65d3..a178173 100644
--- a/drivers/gpu/drm/mxsfb/mxsfb_drv.h
+++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.h
@@ -32,6 +32,8 @@ struct mxsfb_drm_private {
 	struct drm_connector		*connector;
 	struct drm_panel		*panel;
 	struct drm_bridge		*bridge;
+
+	u32				max_bw;
 };
 
 int mxsfb_setup_crtc(struct drm_device *dev);
-- 
2.7.4