MLK-16906: drm: imx: core: add possiblity to detect if chip has DCSS

The Mscale Display Controller Subsystem does not support RGB565.
However, the default legacy FB pixel depth is 16. Hence, the users would
have to add a kernel cmdline option to set it to 32bpp:
imxdrm.legacyfb_depth=32

This patch changes imx-drm-core to detect if platform has DCSS and, if
it does, set the FB pixel depth to 32, so that user does not have to.

Signed-off-by: Laurentiu Palcu <laurentiu.palcu@nxp.com>

diff --git a/drivers/gpu/drm/imx/imx-drm-core.c b/drivers/gpu/drm/imx/imx-drm-core.c
index 7d91dce..e426a46 100644 (file)
--- a/drivers/gpu/drm/imx/imx-drm-core.c
+++ b/drivers/gpu/drm/imx/imx-drm-core.c
@@ -147,6 +147,44 @@ static int compare_of(struct device *dev, void *data)
        return dev->of_node == np;
 }
 
+static const char *const imx_drm_dcss_comp_parents[] = {
+       "nxp,imx8mq-dcss",
+};
+
+static bool imx_drm_parent_is_compatible(struct device *dev,
+                                        const char *const comp_parents[],
+                                        int comp_parents_size)
+{
+       struct device_node *port, *parent;
+       bool ret = false;
+       int i;
+
+       port = of_parse_phandle(dev->of_node, "ports", 0);
+       if (!port)
+               return ret;
+
+       parent = of_get_parent(port);
+
+       for (i = 0; i < comp_parents_size; i++) {
+               if (of_device_is_compatible(parent, comp_parents[i])) {
+                       ret = true;
+                       break;
+               }
+       }
+
+       of_node_put(parent);
+
+       of_node_put(port);
+
+       return ret;
+}
+
+static inline bool has_dcss(struct device *dev)
+{
+       return imx_drm_parent_is_compatible(dev, imx_drm_dcss_comp_parents,
+                                       ARRAY_SIZE(imx_drm_dcss_comp_parents));
+}
+
 static int imx_drm_bind(struct device *dev)
 {
        struct drm_device *drm;
@@ -202,8 +240,13 @@ static int imx_drm_bind(struct device *dev)
                dev_warn(dev, "Invalid legacyfb_depth.  Defaulting to 16bpp\n");
                legacyfb_depth = 16;
        }
+
+       if (legacyfb_depth == 16 && has_dcss(dev))
+               legacyfb_depth = 32;
+
        ret = drm_fb_cma_fbdev_init(drm, legacyfb_depth, MAX_CRTC);
        if (ret)
+
                goto err_unbind;
 #endif