arm: K3: Avoid use of MCU_PSRAM0 before SYSFW is loaded

On HS devices the 512b region of reset isolated memory called
MCU_PSRAM0 is firewalled by default. Until SYSFW is loaded we
cannot use this memory. It is only used to store a single value
left at the end of SRAM by ROM that will be needed later. Save
that value to a global variable stored in the .data section.
This section is used as .bss will be cleared between saving
this value and using it.
Signed-off-by: NAndrew F. Davis <afd@ti.com>
Reviewed-by: NAndreas Dannenberg <dannenberg@ti.com>
Reviewed-by: NLokesh Vutla <lokeshvutla@ti.com>

arch/arm/mach-k3/am6_init.c

@@ -49,11 +49,16 @@ static void ctrl_mmr_unlock(void)
 	mmr_unlock(CTRL_MMR0_BASE, 7);
 }
 
+/*
+ * This uninitialized global variable would normal end up in the .bss section,
+ * but the .bss is cleared between writing and reading this variable, so move
+ * it to the .data section.
+ */
+u32 bootindex __attribute__((section(".data")));
+
 static void store_boot_index_from_rom(void)
 {
-	u32 *boot_index = (u32 *)K3_BOOT_PARAM_TABLE_INDEX_VAL;
-
-	*boot_index = *(u32 *)(CONFIG_SYS_K3_BOOT_PARAM_TABLE_INDEX);
+	bootindex = *(u32 *)(CONFIG_SYS_K3_BOOT_PARAM_TABLE_INDEX);
 }
 
 void board_init_f(ulong dummy)
@@ -92,7 +97,6 @@ u32 spl_boot_mode(const u32 boot_device)
 {
 #if defined(CONFIG_SUPPORT_EMMC_BOOT)
 	u32 devstat = readl(CTRLMMR_MAIN_DEVSTAT);
-	u32 bootindex = readl(K3_BOOT_PARAM_TABLE_INDEX_VAL);
 
 	u32 bootmode = (devstat & CTRLMMR_MAIN_DEVSTAT_BOOTMODE_MASK) >>
 			CTRLMMR_MAIN_DEVSTAT_BOOTMODE_SHIFT;
@@ -168,7 +172,6 @@ static u32 __get_primary_bootmedia(u32 devstat)
 u32 spl_boot_device(void)
 {
 	u32 devstat = readl(CTRLMMR_MAIN_DEVSTAT);
-	u32 bootindex = readl(K3_BOOT_PARAM_TABLE_INDEX_VAL);
 
 	if (bootindex == K3_PRIMARY_BOOTMODE)
 		return __get_primary_bootmedia(devstat);

arch/arm/mach-k3/include/mach/am6_hardware.h

@@ -44,7 +44,4 @@
 #define CTRLMMR_LOCK_KICK1				0x0100c
 #define CTRLMMR_LOCK_KICK1_UNLOCK_VAL			0xd172bc5a
 
-/* MCU SCRATCHPAD usage */
-#define K3_BOOT_PARAM_TABLE_INDEX_VAL	CONFIG_SYS_K3_MCU_SCRATCHPAD_BASE
-
 #endif /* __ASM_ARCH_AM6_HARDWARE_H */