warmboot: add fuse bypass init

exosphere/lp0fw/src/fuse.c

@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2018 Atmosphère-NX
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+ 
+#include <stdint.h>
+
+#include "utils.h"
+#include "fuse.h"
+#include "car.h"
+#include "pmc.h"
+
+#define NUM_FUSE_BYPASS_ENTRIES 0
+
+bool fuse_check_downgrade_status(void) {
+    /* We aren't going to implement anti-downgrade. */
+    return false;
+}
+
+static fuse_bypass_data_t g_fuse_bypass_entries[NUM_FUSE_BYPASS_ENTRIES] = {
+    /* No entries here. */
+};
+
+void fuse_configure_fuse_bypass(void) {
+    /* Enable fuses in CAR? This seems to affect fuse data visibility. */
+    CLK_RST_CONTROLLER_MISC_CLK_ENB_0 |= 0x10000000;
+    
+    /* Configure bypass/override, only if programming is allowed.  */
+    if (!(FUSE_REGS->FUSE_DIS_PGM & 1)) {
+        /* Enable write access. */
+        FUSE_REGS->FUSE_WRITE_ACCESS = (FUSE_REGS->FUSE_WRITE_ACCESS & ~0x1) | 0x10000;
+        /* Enable fuse bypass config. */
+        FUSE_REGS->FUSE_FUSEBYPASS = 1;
+        
+        /* Override fuses. */
+        for (size_t i = 0; i < NUM_FUSE_BYPASS_ENTRIES; i++) {
+            MAKE_FUSE_REG(g_fuse_bypass_entries[i].offset) = g_fuse_bypass_entries[i].value;
+        }
+        
+        /* Disable fuse write access. */
+        FUSE_REGS->FUSE_WRITE_ACCESS |= 1;
+        
+        /* Enable fuse bypass config. */
+        /* I think this is a bug, and Nintendo meant to write 0 here? */
+        FUSE_REGS->FUSE_FUSEBYPASS = 1;
+        
+        /* This...clears the disable programming bit(?). */
+        /* I have no idea why this happens. What? */
+        /* This is probably also either a bug or does nothing. */
+        /* Is this bit even clearable? */
+        FUSE_REGS->FUSE_DIS_PGM &= 0xFFFFFFFE;
+        
+        /* Restore saved private key disable bit. */
+        FUSE_REGS->FUSE_PRIVATEKEYDISABLE |= (APBDEV_PMC_SECURE_SCRATCH21_0 & 0x10);
+        
+        /* Lock private key disable secure scratch. */
+        APBDEV_PMC_SEC_DISABLE2_0 |= 0x4000000;
+    }
+    
+}