Add support for TI AM625 and AM62A arm64 SoCs

- TI AM625: https://www.ti.com/lit/pdf/spruiv7
- TI AM62a: https://www.ti.com/lit/pdf/spruj16

- fixes #12

Author: thom-nic

src/Makefile.am

@@ -1,6 +1,9 @@
 AM_CFLAGS               = -std=c99 -pedantic -W -Wall -Wextra -Wno-unused-parameter -Wshadow
 
 sbin_PROGRAMS           = bootcount
-bootcount_SOURCES       = bootcount.c am33xx.c stm32mp1.c i2c_eeprom.c memory.c \
-                          dt.c imx8m.c imx93.c
+bootcount_SOURCES       = bootcount.c dt.c memory.c \
+                          am33xx.c am62x.c \
+                          stm32mp1.c \
+                          i2c_eeprom.c\
+                          imx8m.c imx93.c
 

src/am62x.c

@@ -0,0 +1,94 @@
+/**
+ * Access and reset u-boot's "bootcount" counter for the TI AM625 and AM62A SoCs
+ * which is stored in the RTC_SCRATCH2_REG.
+ *
+ * see:
+ * - AM625 TRM: https://www.ti.com/lit/pdf/spruiv7
+ *   Section 12.7.3.3.4 Scratch Registers
+ *   Section 14.8.7.3.12.1 RTC_RTC_SCRATCH0_N Register
+ *
+ * - AM62ax TRM: https://www.ti.com/lit/pdf/spruj16
+ *   Section 12.8.3.3.4 Scratch Registers
+ *   Section 14.9.7.3.12.1 RTC_RTC_SCRATCH0_N Register
+ */
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "./constants.h"
+#include "./memory.h"
+#include "./dt.h"
+#include "./am62x.h"
+
+// spruiv7.pdf Section 14.8.7.3.12 RTC_RTC_RTC_SCRATCH0_N Register
+// spruj16.pdf Section 14.9.7.3.12 RTC_RTC_RTC_SCRATCH0_N Register
+#define AM62_RTCSS                0x2B1F0000ul
+#define AM62_REG_SIZE             4ul          // registers are 4 bytes/ 32bit
+// Offset = 30h + (j * 4h); where j = 0h to 7h:
+#define AM62_SCRATCH2_REG_OFFSET  (0x30ul + 2*AM62_REG_SIZE)
+
+// spruiv7.pdf Section 14.8.7.3.19 RTC_RTC_RTC_KICK0 Registers
+// spruj16.pdf Section 14.9.7.3.19 RTC_RTC_RTC_KICK0 Registers
+#define AM62_KICK0R_REG_OFFSET 0x70ul
+#define AM62_KICK1R_REG_OFFSET 0x74ul
+#define AM62_KICK0_MAGIC       0x83e70b13ul
+#define AM62_KICK1_MAGIC       0x95a4f1e0ul
+
+#define AM62_MEM_OFFSET (AM62_RTCSS + AM62_SCRATCH2_REG_OFFSET)
+// We need to map the RTCSS block from SCRATCH2 up to the end of KICK1R:
+#define AM62_MEM_LEN    (AM62_KICK1R_REG_OFFSET + AM62_REG_SIZE - AM62_SCRATCH2_REG_OFFSET)
+
+bool is_am62() {
+    return is_compatible_soc("ti,am625") || is_compatible_soc("ti,am62a7");
+}
+
+int am62_read_bootcount(uint16_t* val) {
+
+    uint32_t *scratch2_addr = memory_open(AM62_MEM_OFFSET, AM62_MEM_LEN);
+    if ( scratch2_addr == (void *)E_DEVICE ) {
+        return E_DEVICE;
+    }
+
+    uint32_t scratch2_val = memory_read(scratch2_addr);
+    // low two bytes are the value, high two bytes are magic
+    if ((scratch2_val & 0xffff0000) != (BOOTCOUNT_MAGIC & 0xffff0000)) {
+        return E_BADMAGIC;
+    }
+
+    *val = (uint16_t)(scratch2_val & 0x0000ffff);
+    return 0;
+}
+
+
+int am62_write_bootcount(uint16_t val) {
+    // NOTE: These must be volatile.
+    // See https://github.com/brgl/busybox/blob/master/miscutils/devmem.c
+    volatile uint32_t *scratch2_addr =
+        (volatile uint32_t *)memory_open(AM62_MEM_OFFSET, AM62_MEM_LEN);
+    if ( scratch2_addr == (void *)E_DEVICE ) {
+        return E_DEVICE;
+    }
+
+    volatile uint32_t *kick0r = scratch2_addr + (AM62_KICK0R_REG_OFFSET - AM62_SCRATCH2_REG_OFFSET) / 4;
+    volatile uint32_t *kick1r = kick0r + 1; // (AM62_KICK1R_REG_OFFSET - AM62_SCRATCH2_REG_OFFSET) / 4;
+
+    // Disable write protection, then write to SCRATCH2
+    *kick0r = AM62_KICK0_MAGIC;
+    *kick1r = AM62_KICK1_MAGIC;
+    uint32_t scratch2_val = (BOOTCOUNT_MAGIC & 0xffff0000) | (val & 0xffff);
+    memory_write(scratch2_addr, scratch2_val);
+
+    // re-lock the write protection register
+    *kick1r = 0;
+
+    // read back to verify:
+    uint16_t read_val = 0;
+    am62_read_bootcount(&read_val);
+    if ( read_val != val ) {
+        return E_WRITE_FAILED;
+    }
+
+    return 0;
+}

src/am62x.h

@@ -0,0 +1,9 @@
+# pragma once
+
+#include <stdbool.h>
+
+#define AM62_PLAT_NAME "TI AM62x"
+
+bool is_am62();
+int am62_read_bootcount(uint16_t* val);
+int am62_write_bootcount(uint16_t val);

src/bootcount.c

@@ -30,6 +30,7 @@
 #include "constants.h"
 #include "dt.h"
 #include "am33xx.h"
+#include "am62x.h"
 #include "imx8m.h"
 #include "imx93.h"
 #include "stm32mp1.h"
@@ -50,6 +51,11 @@ static const struct platform platforms[] = {
      .read_bootcount = am33_read_bootcount,
      .write_bootcount = am33_write_bootcount
     },
+    {.name = AM62_PLAT_NAME,
+     .detect = is_am62,
+     .read_bootcount = am62_read_bootcount,
+     .write_bootcount = am62_write_bootcount
+    },
     {.name = IMX8M_PLAT_NAME,
      .detect = is_imx8m,
      .read_bootcount = imx8m_read_bootcount,