kboot: lock dart-disp0 to prevent accidental resets

This prevents older systems from resetting dart-disp0 on init when they
encounter device trees with DCP/disp nodes.

Signed-off-by: Janne Grunau <j@jannau.net>

src/dart.c

@@ -321,6 +321,31 @@ dart_dev_t *dart_init_adt(const char *path, int instance, int device, bool keep_
     return dart;
 }
 
+void dart_lock_adt(const char *path, int instance)
+{
+    int dart_path[8];
+    int node = adt_path_offset_trace(adt, path, dart_path);
+    if (node < 0) {
+        printf("dart: Error getting DART node %s\n", path);
+        return;
+    }
+
+    u64 base;
+    if (adt_get_reg(adt, dart_path, "reg", instance, &base, NULL) < 0) {
+        printf("dart: Error getting DART %s base address.\n", path);
+        return;
+    }
+
+    if (adt_is_compatible(adt, node, "dart,t8020") || adt_is_compatible(adt, node, "dart,t6000")) {
+        if (!(read32(base + DART_T8020_CONFIG) & DART_T8020_CONFIG_LOCK))
+            set32(base + DART_T8020_CONFIG, DART_T8020_CONFIG_LOCK);
+    } else if (adt_is_compatible(adt, node, "dart,t8110")) {
+        printf("dart: dart %s, locking ignored for t8110\n", path);
+    } else {
+        printf("dart: dart %s at 0x%lx is of an unknown type\n", path, base);
+    }
+}
+
 dart_dev_t *dart_init_fdt(void *dt, u32 phandle, int device, bool keep_pts)
 {
     int node = fdt_node_offset_by_phandle(dt, phandle);

src/dart.h

@@ -18,6 +18,7 @@ enum dart_type_t {
 
 dart_dev_t *dart_init(uintptr_t base, u8 device, bool keep_pts, enum dart_type_t type);
 dart_dev_t *dart_init_adt(const char *path, int instance, int device, bool keep_pts);
+void dart_lock_adt(const char *path, int instance);
 dart_dev_t *dart_init_fdt(void *dt, u32 phandle, int device, bool keep_pts);
 int dart_setup_pt_region(dart_dev_t *dart, const char *path, int device);
 int dart_map(dart_dev_t *dart, uintptr_t iova, void *bfr, size_t len);

src/kboot.c

@@ -870,6 +870,14 @@ static int dt_set_atc_tunables(void)
     return 0;
 }
 
+static int dt_set_display(void)
+{
+    /* lock dart-disp0 to prevent old software from resetting it */
+    dart_lock_adt("/arm-io/dart-disp0", 0);
+
+    return 0;
+}
+
 static int dt_disable_missing_devs(const char *adt_prefix, const char *dt_prefix, int max_devs)
 {
     int ret = -1;
@@ -1096,6 +1104,8 @@ int kboot_prepare_dt(void *fdt)
         return -1;
     if (dt_set_atc_tunables())
         return -1;
+    if (dt_set_display())
+        return -1;
     if (dt_disable_missing_devs("usb-drd", "usb@", 8))
         return -1;
     if (dt_disable_missing_devs("i2c", "i2c@", 8))