uboot can access tzpc registers?

itop exynos 4412 board with customized uboot :

In uboot's source code lowlevel_init_SCP.S,we can see tzsc registers initialized by  tzpc_init routine which means uboot has ability to access this controller.Uboot start up porcess is also good and smooth.But after entered the uboot command line environment,,I use "md 0x10110000  1"  command to display tzpc 's first register value,the uboot freeze there maybe indicated a data abort exception.I wondered why this would happened?

ATF document has show us uboot run on normal world,but how could uboot can access secure world  component  tzsc during uboot's startup?if secure firmware set tzsc address to normal world,why access to it from command line failed?

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