arm: mach-k3: am62: Fixup CPU core, gpu and pru nodes in fdt

AM62x SoC is available in multiple variant:
- CPU cores (Cortex-A) AM62x1 (1 core), AM62x2 (2 cores), AM62x4 (4 cores)
- GPU AM625x with GPU, AM623x without GPU
- PRU (Programmable RT unit) can be present or not on AM62x2/AM62x4

Remove the relevant FDT nodes by reading the actual configuration
from the SoC registers, with that change is possible to have a single
dts/dtb file handling the different variant at runtime.
While removing GPU node and CPU nodes also the watchdog node
in the same Module Domain is removed.

A similar approach is implemented for example on i.MX8 and STM32MP1 SoC.

Signed-off-by: Emanuele Ghidoli <emanuele.ghidoli@toradex.com>
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>

arch/arm/mach-k3/Makefile

@@ -15,6 +15,7 @@ ifeq ($(CONFIG_OF_LIBFDT)$(CONFIG_OF_SYSTEM_SETUP),yy)
 obj-$(CONFIG_SOC_K3_AM654) += am654_fdt.o
 obj-$(CONFIG_SOC_K3_J721E) += j721e_fdt.o
 obj-$(CONFIG_SOC_K3_J721S2) += j721s2_fdt.o
+obj-$(CONFIG_SOC_K3_AM625) += am625_fdt.o
 endif
 ifeq ($(CONFIG_SPL_BUILD),y)
 obj-$(CONFIG_SOC_K3_AM654) += am654_init.o

arch/arm/mach-k3/am625_fdt.c

@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright 2023 Toradex - https://www.toradex.com/
+ */
+
+#include <asm/hardware.h>
+#include "common_fdt.h"
+#include <fdt_support.h>
+
+static void fdt_fixup_cores_nodes_am625(void *blob, int core_nr)
+{
+	char node_path[32];
+
+	if (core_nr < 1)
+		return;
+
+	for (; core_nr < 4; core_nr++) {
+		snprintf(node_path, sizeof(node_path), "/cpus/cpu@%d", core_nr);
+		fdt_del_node_path(blob, node_path);
+		snprintf(node_path, sizeof(node_path), "/cpus/cpu-map/cluster0/core%d", core_nr);
+		fdt_del_node_path(blob, node_path);
+		snprintf(node_path, sizeof(node_path), "/bus@f0000/watchdog@e0%d0000", core_nr);
+		fdt_del_node_path(blob, node_path);
+	}
+}
+
+static void fdt_fixup_gpu_nodes_am625(void *blob, int has_gpu)
+{
+	if (!has_gpu) {
+		fdt_del_node_path(blob, "/bus@f0000/gpu@fd00000");
+		fdt_del_node_path(blob, "/bus@f0000/watchdog@e0f0000");
+	}
+}
+
+static void fdt_fixup_pru_node_am625(void *blob, int has_pru)
+{
+	if (!has_pru)
+		fdt_del_node_path(blob, "/bus@f0000/pruss@30040000");
+}
+
+static int k3_get_core_nr(void)
+{
+	u32 full_devid = readl(CTRLMMR_WKUP_JTAG_DEVICE_ID);
+
+	return (full_devid & JTAG_DEV_CORE_NR_MASK) >> JTAG_DEV_CORE_NR_SHIFT;
+}
+
+static int k3_has_pru(void)
+{
+	u32 full_devid = readl(CTRLMMR_WKUP_JTAG_DEVICE_ID);
+	u32 feature_mask = (full_devid & JTAG_DEV_FEATURES_MASK) >>
+			   JTAG_DEV_FEATURES_SHIFT;
+
+	return !(feature_mask & JTAG_DEV_FEATURE_NO_PRU);
+}
+
+static int k3_has_gpu(void)
+{
+	u32 full_devid = readl(CTRLMMR_WKUP_JTAG_DEVICE_ID);
+
+	return (full_devid & JTAG_DEV_GPU_MASK) >> JTAG_DEV_GPU_SHIFT;
+}
+
+int ft_system_setup(void *blob, struct bd_info *bd)
+{
+	fdt_fixup_cores_nodes_am625(blob, k3_get_core_nr());
+	fdt_fixup_gpu_nodes_am625(blob, k3_has_gpu());
+	fdt_fixup_pru_node_am625(blob, k3_has_pru());
+
+	return 0;
+}

arch/arm/mach-k3/common_fdt.c

@@ -93,3 +93,21 @@ int fdt_fixup_msmc_ram_k3(void *blob)
 
 	return ret;
 }
+
+int fdt_del_node_path(void *blob, const char *path)
+{
+	int ret;
+	int nodeoff;
+
+	nodeoff = fdt_path_offset(blob, path);
+	if (nodeoff < 0)
+		return 0; /* Not found, skip it */
+
+	ret = fdt_del_node(blob, nodeoff);
+	if (ret < 0)
+		printf("Unable to delete node %s, err=%s\n", path, fdt_strerror(ret));
+	else
+		debug("Deleted node %s\n", path);
+
+	return ret;
+}