Call platform_is_primary_cpu() only from reset handler

The purpose of platform_is_primary_cpu() is to determine after reset
(BL1 or BL3-1 with reset handler) if the current CPU must follow the
cold boot path (primary CPU), or wait in a safe state (secondary CPU)
until the primary CPU has finished the system initialization.

This patch removes redundant calls to platform_is_primary_cpu() in
subsequent bootloader entrypoints since the reset handler already
guarantees that code is executed exclusively on the primary CPU.

Additionally, this patch removes the weak definition of
platform_is_primary_cpu(), so the implementation of this function
becomes mandatory. Removing the weak symbol avoids other
bootloaders accidentally picking up an invalid definition in case the
porting layer makes the real function available only to BL1.

The define PRIMARY_CPU is no longer mandatory in the platform porting
because platform_is_primary_cpu() hides the implementation details
(for instance, there may be platforms that report the primary CPU in
a system register). The primary CPU definition in FVP has been moved
to fvp_def.h.

The porting guide has been updated accordingly.

Fixes ARM-software/tf-issues#219

Change-Id: If675a1de8e8d25122b7fef147cb238d939f90b5e

8 files changed, 19 insertions, 61 deletions

diff --git a/bl2/aarch64/bl2_entrypoint.S b/bl2/aarch64/bl2_entrypoint.S
index 6fcd040..d3b0f55 100644
--- a/bl2/aarch64/bl2_entrypoint.S
+++ b/bl2/aarch64/bl2_entrypoint.S
@@ -48,16 +48,6 @@ func bl2_entrypoint
 	mov	x21, x1
 
 	/* ---------------------------------------------
-	 * This is BL2 which is expected to be executed
-	 * only by the primary cpu (at least for now).
-	 * So, make sure no secondary has lost its way.
-	 * ---------------------------------------------
-	 */
-	mrs	x0, mpidr_el1
-	bl	platform_is_primary_cpu
-	cbz	x0, _panic
-
-	/* ---------------------------------------------
 	 * Set the exception vector to something sane.
 	 * ---------------------------------------------
 	 */
diff --git a/bl31/aarch64/bl31_entrypoint.S b/bl31/aarch64/bl31_entrypoint.S
index fb8fd2c..c3a09bf 100644
--- a/bl31/aarch64/bl31_entrypoint.S
+++ b/bl31/aarch64/bl31_entrypoint.S
@@ -129,16 +129,6 @@ func bl31_entrypoint
 	 */
 	wait_for_entrypoint
 	bl	platform_mem_init
-#else
-	/* ---------------------------------------------
-	 * This is BL31 which is expected to be executed
-	 * only by the primary cpu (at least for now).
-	 * So, make sure no secondary has lost its way.
-	 * ---------------------------------------------
-	 */
-	mrs	x0, mpidr_el1
-	bl	platform_is_primary_cpu
-	cbz	x0, _panic
 #endif
 
 	/* ---------------------------------------------
diff --git a/bl32/tsp/aarch64/tsp_entrypoint.S b/bl32/tsp/aarch64/tsp_entrypoint.S
index 91b6128..75ee443 100644
--- a/bl32/tsp/aarch64/tsp_entrypoint.S
+++ b/bl32/tsp/aarch64/tsp_entrypoint.S
@@ -72,16 +72,6 @@
 func tsp_entrypoint
 
 	/* ---------------------------------------------
-	 * The entrypoint is expected to be executed
-	 * only by the primary cpu (at least for now).
-	 * So, make sure no secondary has lost its way.
-	 * ---------------------------------------------
-	 */
-	mrs	x0, mpidr_el1
-	bl	platform_is_primary_cpu
-	cbz	x0, tsp_entrypoint_panic
-
-	/* ---------------------------------------------
 	 * Set the exception vector to something sane.
 	 * ---------------------------------------------
 	 */
diff --git a/docs/porting-guide.md b/docs/porting-guide.md
index c711590..db2bad8 100644
--- a/docs/porting-guide.md
+++ b/docs/porting-guide.md
@@ -150,11 +150,6 @@ file is found in [plat/fvp/include/platform_def.h].
     Defines the total number of nodes in the affinity heirarchy at all affinity
     levels used by the platform.
 
-*   **#define : PRIMARY_CPU**
-
-    Defines the `MPIDR` of the primary CPU on the platform. This value is used
-    after a cold boot to distinguish between primary and secondary CPUs.
-
 *   **#define : TZROM_BASE**
 
     Defines the base address of secure ROM on the platform, where the BL1 binary
@@ -360,6 +355,17 @@ requires them.
 This function fulfills requirement 2 above.
 
 
+### Function : platform_is_primary_cpu() [mandatory]
+
+    Argument : unsigned long
+    Return   : unsigned int
+
+This function identifies a CPU by its `MPIDR`, which is passed as the argument,
+to determine whether this CPU is the primary CPU or a secondary CPU. A return
+value of zero indicates that the CPU is not the primary CPU, while a non-zero
+return value indicates that the CPU is the primary CPU.
+
+
 ### Function : platform_mem_init() [mandatory]
 
     Argument : void
@@ -398,17 +404,6 @@ maximum of 4 CPUs:
     cluster_id = 8-bit value in MPIDR at affinity level 1
 
 
-### Function : platform_is_primary_cpu()
-
-    Argument : unsigned long
-    Return   : unsigned int
-
-This function identifies a CPU by its `MPIDR`, which is passed as the argument,
-to determine whether this CPU is the primary CPU or a secondary CPU. A return
-value of zero indicates that the CPU is not the primary CPU, while a non-zero
-return value indicates that the CPU is the primary CPU.
-
-
 ### Function : platform_set_stack()
 
     Argument : unsigned long
diff --git a/plat/common/aarch64/platform_helpers.S b/plat/common/aarch64/platform_helpers.S
index 5e2d1b1..6dc4ec6 100644
--- a/plat/common/aarch64/platform_helpers.S
+++ b/plat/common/aarch64/platform_helpers.S
@@ -34,7 +34,6 @@
 
 
 	.weak	platform_get_core_pos
-	.weak	platform_is_primary_cpu
 	.weak	platform_check_mpidr
 	.weak	plat_report_exception
 	.weak	plat_crash_console_init
@@ -53,19 +52,6 @@ func platform_get_core_pos
 	ret
 
 	/* -----------------------------------------------------
-	 * void platform_is_primary_cpu (unsigned int mpid);
-	 *
-	 * Given the mpidr say whether this cpu is the primary
-	 * cpu (applicable ony after a cold boot)
-	 * -----------------------------------------------------
-	 */
-func platform_is_primary_cpu
-	and	x0, x0, #(MPIDR_CLUSTER_MASK | MPIDR_CPU_MASK)
-	cmp	x0, #PRIMARY_CPU
-	cset	x0, eq
-	ret
-
-	/* -----------------------------------------------------
 	 * Placeholder function which should be redefined by
 	 * each platform.
 	 * -----------------------------------------------------
diff --git a/plat/fvp/aarch64/fvp_helpers.S b/plat/fvp/aarch64/fvp_helpers.S
index 823588e..4011306 100644
--- a/plat/fvp/aarch64/fvp_helpers.S
+++ b/plat/fvp/aarch64/fvp_helpers.S
@@ -40,6 +40,7 @@
 	.globl	plat_secondary_cold_boot_setup
 	.globl	platform_mem_init
 	.globl	plat_report_exception
+	.globl	platform_is_primary_cpu
 	.globl	plat_crash_console_init
 	.globl	plat_crash_console_putc
 
@@ -191,6 +192,12 @@ func plat_report_exception
 	str	w0, [x1]
 	ret
 
+func platform_is_primary_cpu
+	and	x0, x0, #(MPIDR_CLUSTER_MASK | MPIDR_CPU_MASK)
+	cmp	x0, #FVP_PRIMARY_CPU
+	cset	x0, eq
+	ret
+
 	/* Define a crash console for the plaform */
 #define FVP_CRASH_CONSOLE_BASE		PL011_UART0_BASE
 
diff --git a/plat/fvp/fvp_def.h b/plat/fvp/fvp_def.h
index 21edb3b..a757b4d 100644
--- a/plat/fvp/fvp_def.h
+++ b/plat/fvp/fvp_def.h
@@ -36,6 +36,7 @@
 
 /* Firmware Image Package */
 #define FIP_IMAGE_NAME			"fip.bin"
+#define FVP_PRIMARY_CPU			0x0
 
 /*******************************************************************************
  * FVP memory map related constants
diff --git a/plat/fvp/include/platform_def.h b/plat/fvp/include/platform_def.h
index 9983266..70f84bb 100644
--- a/plat/fvp/include/platform_def.h
+++ b/plat/fvp/include/platform_def.h
@@ -70,7 +70,6 @@
 #define PLATFORM_MAX_CPUS_PER_CLUSTER	4
 #define PLATFORM_NUM_AFFS		(PLATFORM_CLUSTER_COUNT + \
 					 PLATFORM_CORE_COUNT)
-#define PRIMARY_CPU			0x0
 #define MAX_IO_DEVICES			3
 #define MAX_IO_HANDLES			4