Tegra194: memctrl: fix logic to check TZDRAM config register access

This patch fixes the logic to check if the previous bootloader has
disabled access to the TZDRAM configuration registers. The polarity
for the bit was incorrect in the previous check.

Change-Id: I7a0ba4f7b1714997508ece904c0261ca2c901a03
Signed-off-by: Steven Kao <skao@nvidia.com>

plat/nvidia/tegra/include/t194/tegra_def.h

@@ -75,6 +75,8 @@
 
 #define MC_SECURITY_CFG_REG_CTRL_0	U(0x154)
 #define  SECURITY_CFG_WRITE_ACCESS_BIT	(U(0x1) << 0)
+#define  SECURITY_CFG_WRITE_ACCESS_ENABLE	U(0x0)
+#define  SECURITY_CFG_WRITE_ACCESS_DISABLE	U(0x1)
 
 /* Video Memory carveout configuration registers */
 #define MC_VIDEO_PROTECT_BASE_HI	U(0x978)

plat/nvidia/tegra/soc/t194/plat_memctrl.c

@@ -646,12 +646,14 @@ tegra_mc_settings_t *tegra_get_mc_settings(void)
  ******************************************************************************/
 void plat_memctrl_tzdram_setup(uint64_t phys_base, uint64_t size_in_bytes)
 {
+	uint32_t sec_reg_ctrl = tegra_mc_read_32(MC_SECURITY_CFG_REG_CTRL_0);
+
 	/*
-	 * Check if the carveout register is already locked, if locked
-	 * no TZDRAM setup
+	 * Check TZDRAM carveout register access status. Setup TZDRAM fence
+	 * only if access is enabled.
 	 */
-	if ((tegra_mc_read_32(MC_SECURITY_CFG_REG_CTRL_0) &
-		SECURITY_CFG_WRITE_ACCESS_BIT) == SECURITY_CFG_WRITE_ACCESS_BIT) {
+	if ((sec_reg_ctrl & SECURITY_CFG_WRITE_ACCESS_BIT) ==
+	     SECURITY_CFG_WRITE_ACCESS_ENABLE) {
 
 		/*
 		 * Setup the Memory controller to allow only secure accesses to