drm/stm: ltdc: handle lvds pixel clock

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>
Acked-by: Yannick Fertre <yannick.fertre@foss.st.com>
Acked-by: Philippe Cornu <philippe.cornu@foss.st.com>
Link: https://lore.kernel.org/r/20250822-drm-misc-next-v5-8-9c825e28f733@foss.st.com
Signed-off-by: Raphael Gallais-Pou <raphael.gallais-pou@foss.st.com>

diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
index 9970bcb748eac2c3453eb752e0411d560c7d1c76..d1501e86a5b1c3fd5e8791a2143616a66850a62b 100644 (file)
--- a/drivers/gpu/drm/stm/ltdc.c
+++ b/drivers/gpu/drm/stm/ltdc.c
@@ -838,6 +838,12 @@ 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_dbg_driver(crtc->dev, "clk rate target %d, available %d\n", target, result);
@@ -1879,6 +1885,8 @@ 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)
@@ -1896,8 +1904,16 @@ 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;
@@ -1982,6 +1998,10 @@ 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 (file)
--- 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;