armv7a: re-read ttb information if ttbcr changes

If ttbcr is changed after the debugger has examined a target for the
first time, address translations may fail. This problem does not show up
with Linux because it doesn't use ttbr1, but it shows with other OS that
use this feature. If the debugger connects to the target while it's in
u-boot, all address translations will fail after the OS has booted and
the target can not be debugged.

This patch reads the ttbcr in armv7a_mmu_translate_va() and compares it
a cached value. If a difference is detected, armv7a_read_ttbcr() is called
to re-parse the ttb configuration and update the cache.

Change-Id: I1c3adf53ea9d748a0e1e3091d9581e5c43ed64e8
Signed-off-by: Matthias Welwarsky <matthias@welwarsky.de>
Reviewed-on: http://openocd.zylin.com/3005
Tested-by: jenkins
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>

2 files changed, 18 insertions, 6 deletions

diff --git a/src/target/armv7a.c b/src/target/armv7a.c
index 170cfcc2..b7878389 100644
--- a/src/target/armv7a.c
+++ b/src/target/armv7a.c
@@ -154,10 +154,11 @@ static int armv7a_read_ttbcr(struct target *target)
 	if (retval != ERROR_OK)
 		goto done;
 
-	LOG_INFO("ttbcr %" PRIx32 "ttbr0 %" PRIx32 "ttbr1 %" PRIx32, ttbcr, ttbr0, ttbr1);
+	LOG_INFO("ttbcr %" PRIx32 " ttbr0 %" PRIx32 " ttbr1 %" PRIx32, ttbcr, ttbr0, ttbr1);
 
 	armv7a->armv7a_mmu.ttbr1_used = ((ttbcr & 0x7) != 0) ? 1 : 0;
 	armv7a->armv7a_mmu.ttbr0_mask = 0;
+	armv7a->armv7a_mmu.ttbcr = ttbcr;
 
 	retval = armv7a_read_midr(target);
 	if (retval != ERROR_OK)
@@ -199,17 +200,27 @@ int armv7a_mmu_translate_va(struct target *target,  uint32_t va, uint32_t *val)
 	struct armv7a_common *armv7a = target_to_armv7a(target);
 	struct arm_dpm *dpm = armv7a->arm.dpm;
 	uint32_t ttb = 0;	/*  default ttb0 */
-	if (armv7a->armv7a_mmu.ttbr1_used == -1)
+	uint32_t ttbcr;
+
+	retval = dpm->prepare(dpm);
+	if (retval != ERROR_OK)
+		goto done;
+
+	/*  MRC p15,0,<Rt>,c2,c0,2 ; Read CP15 Translation Table Base Control Register*/
+	retval = dpm->instr_read_data_r0(dpm,
+			ARMV4_5_MRC(15, 0, 0, 2, 0, 2),
+			&ttbcr);
+	if (retval != ERROR_OK)
+		goto done;
+
+	/* if ttbcr has changed, re-read the information */
+	if (armv7a->armv7a_mmu.ttbcr != ttbcr)
 		armv7a_read_ttbcr(target);
 	if ((armv7a->armv7a_mmu.ttbr1_used) &&
 		(va > (0xffffffff & armv7a->armv7a_mmu.ttbr0_mask))) {
 		/*  select ttb 1 */
 		ttb = 1;
 	}
-	retval = dpm->prepare(dpm);
-	if (retval != ERROR_OK)
-		goto done;
-
 	/*  MRC p15,0,<Rt>,c2,c0,ttb */
 	retval = dpm->instr_read_data_r0(dpm,
 			ARMV4_5_MRC(15, 0, 0, 2, 0, ttb),
diff --git a/src/target/armv7a.h b/src/target/armv7a.h
index 4341acae..db34ca66 100644
--- a/src/target/armv7a.h
+++ b/src/target/armv7a.h
@@ -81,6 +81,7 @@ struct armv7a_mmu_common {
 	int32_t ttbr1_used; /*  -1 not initialized, 0 no ttbr1 1 ttbr1 used and  */
 	uint32_t ttbr0_mask;/*  masked to be used  */
 	uint32_t os_border;
+	uint32_t ttbcr;
 
 	int (*read_physical_memory)(struct target *target, uint32_t address, uint32_t size,
 			uint32_t count, uint8_t *buffer);