rpi3: Do prescaler and control setup in C

To initialise the arch timer configuration and some clock prescaler, we
need to do two MMIO access *once*, early during boot.

As tempting as it may sound, plat_reset_handler() is not the right place
to do this, as it will be called on every CPU coming up, both for
secondary cores as well as during warmboots. So this access will be done
multiple times, and even during a rich OS' runtime. Whether doing so anyway
is actually harmful is hard to say, but we should definitely avoid this if
possible.

Move the initialisation of these registers to C code in
bl1_early_platform_setup(), where it will still be executed early enough
(before enabling the console), but only once during the whole boot
process.

Change-Id: I081c41a5476d424411411488ff8f633e87d3bcc5
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

plat/rpi/rpi3/aarch64/plat_helpers.S

@@ -18,7 +18,6 @@
 	.globl	plat_get_my_entrypoint
 	.globl	plat_is_my_cpu_primary
 	.globl	plat_my_core_pos
-	.globl	plat_reset_handler
 	.globl	plat_rpi3_calc_core_pos
 	.globl	plat_secondary_cold_boot_setup
 
@@ -164,16 +163,3 @@ func plat_crash_console_flush
 	mov_imm	x0, PLAT_RPI3_UART_BASE
 	b	console_16550_core_flush
 endfunc plat_crash_console_flush
-
-	/* ---------------------------------------------
-	 * void plat_reset_handler(void);
-	 * ---------------------------------------------
-	 */
-func plat_reset_handler
-	/* use the 19.2 MHz clock for the architected timer */
-	mov	x0, #RPI3_INTC_BASE_ADDRESS
-	mov	w1, #0x80000000
-	str	wzr, [x0, #RPI3_INTC_CONTROL_OFFSET]
-	str	w1, [x0, #RPI3_INTC_PRESCALER_OFFSET]
-	ret
-endfunc plat_reset_handler

plat/rpi/rpi3/rpi3_bl1_setup.c

@@ -10,6 +10,7 @@
 #include <arch_helpers.h>
 #include <common/bl_common.h>
 #include <common/debug.h>
+#include <lib/mmio.h>
 #include <lib/xlat_tables/xlat_mmu_helpers.h>
 #include <lib/xlat_tables/xlat_tables_defs.h>
 
@@ -28,6 +29,11 @@ meminfo_t *bl1_plat_sec_mem_layout(void)
  ******************************************************************************/
 void bl1_early_platform_setup(void)
 {
+	/* use the 19.2 MHz clock for the architected timer */
+	mmio_write_32(RPI3_INTC_BASE_ADDRESS + RPI3_INTC_CONTROL_OFFSET, 0);
+	mmio_write_32(RPI3_INTC_BASE_ADDRESS + RPI3_INTC_PRESCALER_OFFSET,
+		      0x80000000);
+
 	/* Initialize the console to provide early debug support */
 	rpi3_console_init();