Flash pre-init reboots if it needs to clear protection registers

BUG=chrome-os-partner:11171
TEST=manual

1. Clear some of the writable-bits in the flash registers
> ww 0x400fe40c 0xffff1234
write 0x400fe40c = 0xffff1234
> rw 0x400fe40c
read 0x400fe40c = 0xffff1234
2. Reset using power+refresh
3. Register should be clear again
> rw 0x400fe40c
read 0x400fe40c = 0xffffffff
4. Sysinfo should indicate reset-pin reason AND hard-reset reason
> sysinfo
Reset flags: 0x0000000a (reset-pin power-on)
5. Reset using power+refresh
6. Sysinfo should indicate reset-pin reason only
> sysinfo
Reset flags: 0x00000002 (reset-pin)
7. Clear writable-bits again
> ww 0x400fe40c 0xffff1234
write 0x400fe40c = 0xffff1234
8. Jump to another image.  This should NOT trigger a hard reset.
> sysjump A
> sysinfo
Reset flags: 0x00000402 (reset-pin sysjump)

Change-Id: Ie1d6af2acc68217bb82faae464798ee85d63d1ea
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/27540
Reviewed-by: Bill Richardson <wfrichar@chromium.org>

chip/lm4/flash.c

@@ -7,6 +7,7 @@
 
 #include "flash.h"
 #include "registers.h"
+#include "system.h"
 #include "timer.h"
 #include "util.h"
 #include "watchdog.h"
@@ -180,3 +181,43 @@ void flash_physical_set_protect(int block)
 {
 	LM4_FLASH_FMPPE[F_BANK(block)] &= ~F_BIT(block);
 }
+
+int flash_physical_pre_init(void)
+{
+	int reset_flags = system_get_reset_flags();
+	int any_wp = 0;
+	int i;
+
+	/*
+	 * If we have already jumped between images, an earlier image could
+	 * have applied write protection.  Nothing additional needs to be done.
+	 */
+	if (reset_flags & RESET_FLAG_SYSJUMP)
+		return EC_SUCCESS;
+
+	/* Check if any blocks are currently physically write-protected */
+	for (i = 0; i < (LM4_FLASH_FSIZE + 1) / 32; i++) {
+		if (LM4_FLASH_FMPPE[i] != 0xffffffff) {
+			any_wp = 1;
+			break;
+		}
+	}
+
+	/* If nothing is write-protected, done. */
+	if (!any_wp)
+		return EC_SUCCESS;
+
+	/*
+	 * If the last reboot was a power-on reset, it should have cleared
+	 * write-protect.  If it didn't, then the flash write protect registers
+	 * have been permanently committed and we can't fix that.
+	 */
+	if (reset_flags & RESET_FLAG_POWER_ON)
+		return EC_ERROR_ACCESS_DENIED;
+
+	/* Otherwise, do a hard boot to clear the flash protection registers */
+	system_reset(SYSTEM_RESET_HARD | SYSTEM_RESET_PRESERVE_FLAGS);
+
+	/* That doesn't return, so if we're still here that's an error */
+	return EC_ERROR_UNKNOWN;
+}

chip/stm32/flash-stm32f100.c

@@ -257,3 +257,8 @@ void flash_physical_set_protect(int block)
 	write_optb(byte_off, val);
 	}
 }
+
+int flash_physical_pre_init(void)
+{
+	return EC_SUCCESS;
+}

chip/stm32/flash-stm32l15x.c

@@ -317,3 +317,8 @@ void flash_physical_set_protect(int block)
 	write_optb(byte_off, val);
 	}
 }
+
+int flash_physical_pre_init(void)
+{
+	return EC_SUCCESS;
+}

common/flash_common.c

@@ -272,9 +272,11 @@ int flash_lock_protect(int lock)
 
 const uint8_t *flash_get_protect_array(void)
 {
-	/* Return a copy of the current write protect state.  This is an array
+	/*
+	 * Return a copy of the current write protect state.  This is an array
 	 * of per-protect-block flags.  (This is NOT the actual array, so
-	 * attempting to change it will have no effect.) */
+	 * attempting to change it will have no effect.)
+	 */
 	int pbsize = flash_get_protect_block_size();
 	int banks = usable_flash_size / pbsize;
 	int i;
@@ -345,15 +347,25 @@ int flash_get_protect_lock(void)
 
 int flash_pre_init(void)
 {
+	/* Initialize the physical flash interface */
+	/*
+	 * TODO: track pre-init error so we can report it later.  Do at the
+	 * same time as new flash commands to get/set write protect status.
+	 */
+	flash_physical_pre_init();
+
 #ifdef CHIP_stm32
 	usable_flash_size = flash_physical_size();
 #else
-	/* Calculate usable flash size.  Reserve one protection block
-	 * at the top to hold the "pretend SPI" write protect data. */
+	/*
+	 * Calculate usable flash size.  Reserve one protection block
+	 * at the top to hold the "pretend SPI" write protect data.
+	 */
 	usable_flash_size = flash_physical_size() -
 		flash_get_protect_block_size();
 #endif
 
+
 	/* Apply write protect to blocks if needed */
 	return apply_pstate();
 }

common/main.c

@@ -6,8 +6,8 @@
  */
 
 #include "clock.h"
+#include "common.h"
 #include "cpu.h"
-#include "config.h"
 #include "eeprom.h"
 #include "eoption.h"
 #include "flash.h"
@@ -44,18 +44,6 @@ int main(void)
 	 */
 	task_pre_init();
 
-#ifdef CONFIG_FLASH
-	flash_pre_init();
-#endif
-
-#ifdef CONFIG_VBOOT
-	/*
-	 * Verified boot pre-init.  This write-protects flash if necessary.
-	 * Flash and GPIOs must be initialized first.
-	 */
-	vboot_pre_init();
-#endif
-
 	/*
 	 * Initialize the system module.  This enables the hibernate clock
 	 * source we need to calibrate the internal oscillator.
@@ -63,6 +51,14 @@ int main(void)
 	system_pre_init();
 	system_common_pre_init();
 
+#ifdef CONFIG_FLASH
+	/*
+	 * Initialize flash and apply write protecte if necessary.  Requires
+	 * the reset flags calculated by system initialization.
+	 */
+	flash_pre_init();
+#endif
+
 	/* Set the CPU clocks / PLLs.  System is now running at full speed. */
 	clock_init();
 

common/vboot.c

@@ -15,12 +15,6 @@
 #define CPUTS(outstr) cputs(CC_VBOOT, outstr)
 #define CPRINTF(format, args...) cprintf(CC_VBOOT, format, ## args)
 
-int vboot_pre_init(void)
-{
-	/* FIXME(wfrichar): crosbug.com/p/7453: should protect flash */
-	return EC_SUCCESS;
-}
-
 /****************************************************************************/
 /* Host commands */
 

include/flash.h

@@ -14,6 +14,11 @@
 /*****************************************************************************/
 /* Low-level methods, for use by flash_common. */
 
+/**
+ * Initialize the physical flash interface.
+ */
+int flash_physical_pre_init(void);
+
 /* Return the write / erase / protect block size, in bytes.  Operations must be
  * aligned to and multiples of the granularity.  For example, erase operations
  * must have offset and size which are multiples of the erase block size. */

include/vboot.h

@@ -10,9 +10,6 @@
 
 #include "common.h"
 
-/* Pre-initialize the module.  This occurs before clocks or tasks are set up. */
-int vboot_pre_init(void);
-
 /*
  * Check verified boot signatures, and jump to one of the RW images if
  * necessary.