From: Yannick Fertre <yannick.fertre@foss.st.com>

Handle LVDS pixel clock.

The LTDC operates with multiple clock domains for register access,
requiring all clocks to be provided during read/write operations.  This
imposes a dependency between the LVDS and LTDC to access correctly all
LTDC registers.  And because both IPs' pixel rates must be synchronized,
the LTDC has to handle the LVDS clock.

Signed-off-by: Yannick Fertre <yannick.fertre@foss.st.com>
Signed-off-by: Raphael Gallais-Pou <raphael.gallais-pou@foss.st.com>
---
  drivers/gpu/drm/stm/ltdc.c | 22 +++++++++++++++++++++-
  drivers/gpu/drm/stm/ltdc.h |  1 +
  2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
index 17548dd3484a0a3e1015c58c752b80f8892a0ff7..f84a9a8590f0653e422798ff61804d7c3966caef 100644
--- a/drivers/gpu/drm/stm/ltdc.c
+++ b/drivers/gpu/drm/stm/ltdc.c

@@ -837,6 +837,12 @@ ltdc_crtc_mode_valid(struct drm_crtc *crtc,
  	int target_max = target + CLK_TOLERANCE_HZ;
  	int result;
  
+	if (ldev->lvds_clk) {
+		result = clk_round_rate(ldev->lvds_clk, target);
+		drm_dbg_driver(crtc->dev, "lvds pixclk rate target %d, available %d\n",
+			       target, result);
+	}
+
  	result = clk_round_rate(ldev->pixel_clk, target);
  
  	DRM_DEBUG_DRIVER("clk rate target %d, available %d\n", target, result);

@@ -1878,6 +1884,8 @@ void ltdc_suspend(struct drm_device *ddev)
  	clk_disable_unprepare(ldev->pixel_clk);
  	if (ldev->bus_clk)
  		clk_disable_unprepare(ldev->bus_clk);
+	if (ldev->lvds_clk)
+		clk_disable_unprepare(ldev->lvds_clk);
  }
  
  int ltdc_resume(struct drm_device *ddev)

@@ -1895,8 +1903,16 @@ int ltdc_resume(struct drm_device *ddev)
  
  	if (ldev->bus_clk) {
  		ret = clk_prepare_enable(ldev->bus_clk);
-		if (ret)
+		if (ret) {
  			drm_err(ddev, "failed to enable bus clock (%d)\n", ret);
+			return ret;
+		}
+	}
+
+	if (ldev->lvds_clk) {
+		ret = clk_prepare_enable(ldev->lvds_clk);
+		if (ret)
+			drm_err(ddev, "failed to prepare lvds clock\n");
  	}
  
  	return ret;

@@ -1981,6 +1997,10 @@ int ltdc_load(struct drm_device *ddev)
  		}
  	}
  
+	ldev->lvds_clk = devm_clk_get(dev, "lvds");
+	if (IS_ERR(ldev->lvds_clk))
+		ldev->lvds_clk = NULL;
+
  	rstc = devm_reset_control_get_exclusive(dev, NULL);
  
  	mutex_init(&ldev->err_lock);

diff --git a/drivers/gpu/drm/stm/ltdc.h b/drivers/gpu/drm/stm/ltdc.h
index ddfa8ae61a7ba5dc446fae647562d0ec8e6953e1..17b51a7ce28eee5de6d24ca943ca3b1f48695dfd 100644
--- a/drivers/gpu/drm/stm/ltdc.h
+++ b/drivers/gpu/drm/stm/ltdc.h

@@ -48,6 +48,7 @@ struct ltdc_device {
  	void __iomem *regs;
  	struct regmap *regmap;
  	struct clk *pixel_clk;	/* lcd pixel clock */
+	struct clk *lvds_clk;	/* lvds pixel clock */
  	struct clk *bus_clk;	/* bus clock */
  	struct mutex err_lock;	/* protecting error_status */
  	struct ltdc_caps caps;