Introduce crash console APIs for crash reporting

This patch introduces platform APIs to initialise and
print a character on a designated crash console.
For the FVP platform, PL011_UART0 is the designated
crash console. The platform porting guide is also updated
to document the new APIs.

Change-Id: I5e97d8762082e0c88c8c9bbb479353eac8f11a66

docs/porting-guide.md

@@ -15,6 +15,7 @@ Contents
     *   Boot Loader stage 3-1 (BL3-1)
     *   PSCI implementation (in BL3-1)
     *   Interrupt Management framework (in BL3-1)
+    *   Crash Reporting mechanism (in BL3-1)
 4.  C Library
 5.  Storage abstraction layer
 
@@ -1316,6 +1317,41 @@ interrupts as Group1 interrupts. It reads the group value corresponding to the
 interrupt id from the relevant _Interrupt Group Register_ (`GICD_IGROUPRn`). It
 uses the group value to determine the type of interrupt.
 
+3.5  Crash Reporting mechanism (in BL3-1)
+----------------------------------------------
+BL3-1 implements a crash reporting mechanism which prints the various registers
+of the CPU to enable quick crash analysis and debugging. It requires that a console
+is designated as the crash console by the platform which will used to print the
+register dump.
+
+The following functions must be implemented by the platform if it wants crash reporting
+mechanism in BL3-1. The functions are implemented in assembly so that they can be
+invoked without a C Runtime stack.
+
+### Function : plat_crash_console_init
+
+    Argument : void
+    Return   : int
+
+This API is used by the crash reporting mechanism to intialize the crash console.
+It should only use the general purpose registers x0 to x2 to do the initiaization
+and returns 1 on success.
+
+The FVP port designates the PL011_UART0 as the crash console and calls the
+console_core_init() to initialize the console.
+
+### Function : plat_crash_console_putc
+
+    Argument : int
+    Return   : int
+
+This API is used by the crash reporting mechanism to print a character on the
+designated crash console. It should only use general purpose registers x1 and
+x2 to do its work. The parameter and the return value are in general purpose
+register x0.
+
+The FVP port designates the PL011_UART0 as the crash console and calls the
+console_core_putc() to print the character on the console.
 
 4.  C Library
 -------------

include/common/asm_macros.S

@@ -162,3 +162,36 @@ wait_for_entrypoint:
 	.macro get_up_stack _name, _size
 	ldr x0, =(\_name + \_size)
 	.endm
+
+	/*
+	 * Helper macro to generate the best mov/movk combinations according
+	 * the value to be moved. The 16 bits from '_shift' are tested and
+	 * if not zero, they are moved into '_reg' without affecting
+	 * other bits.
+	 */
+	.macro _mov_imm16 _reg, _val, _shift
+		.if (\_val >> \_shift) & 0xffff
+			.if (\_val & (1 << \_shift - 1))
+				movk	\_reg, (\_val >> \_shift) & 0xffff, LSL \_shift
+			.else
+				mov	\_reg, \_val & (0xffff << \_shift)
+			.endif
+		.endif
+	.endm
+
+	/*
+	 * Helper macro to load arbitrary values into 32 or 64-bit registers
+	 * which generates the best mov/movk combinations. Many base addresses
+	 * are 64KB aligned the macro will eliminate updating bits 15:0 in
+	 * that case
+	 */
+	.macro mov_imm _reg, _val
+		.if (\_val) == 0
+			mov	\_reg, #0
+		.else
+			_mov_imm16	\_reg, (\_val), 0
+			_mov_imm16	\_reg, (\_val), 16
+			_mov_imm16	\_reg, (\_val), 32
+			_mov_imm16	\_reg, (\_val), 48
+		.endif
+	.endm

include/plat/common/platform.h

@@ -72,6 +72,8 @@ uint32_t plat_interrupt_type_to_line(uint32_t type,
 unsigned int platform_get_core_pos(unsigned long mpidr);
 unsigned long platform_get_stack(unsigned long mpidr);
 void plat_report_exception(unsigned long);
+void plat_crash_console_init(unsigned long base_addr);
+int plat_crash_console_putc(int c);
 
 /*******************************************************************************
  * Mandatory BL1 functions

plat/common/aarch64/platform_helpers.S

@@ -37,6 +37,8 @@
 	.weak	platform_is_primary_cpu
 	.weak	platform_check_mpidr
 	.weak	plat_report_exception
+	.weak	plat_crash_console_init
+	.weak	plat_crash_console_putc
 
 	/* -----------------------------------------------------
 	 *  int platform_get_core_pos(int mpidr);
@@ -79,3 +81,20 @@ func platform_check_mpidr
 	 */
 func plat_report_exception
 	ret
+
+	/* -----------------------------------------------------
+	 * Placeholder function which should be redefined by
+	 * each platform.
+	 * -----------------------------------------------------
+	 */
+func plat_crash_console_init
+	mov	x0, #0
+	ret
+
+	/* -----------------------------------------------------
+	 * Placeholder function which should be redefined by
+	 * each platform.
+	 * -----------------------------------------------------
+	 */
+func plat_crash_console_putc
+	ret

plat/fvp/aarch64/fvp_helpers.S

@@ -32,6 +32,7 @@
 #include <asm_macros.S>
 #include <bl_common.h>
 #include <gic_v2.h>
+#include <pl011.h>
 #include "../drivers/pwrc/fvp_pwrc.h"
 #include "../fvp_def.h"
 
@@ -39,6 +40,8 @@
 	.globl	plat_secondary_cold_boot_setup
 	.globl	platform_mem_init
 	.globl	plat_report_exception
+	.globl	plat_crash_console_init
+	.globl	plat_crash_console_putc
 
 	.macro	fvp_choose_gicmmap  param1, param2, x_tmp, w_tmp, res
 	ldr	\x_tmp, =VE_SYSREGS_BASE + V2M_SYS_ID
@@ -187,3 +190,30 @@ func plat_report_exception
 	add	x1, x1, #V2M_SYS_LED
 	str	w0, [x1]
 	ret
+
+	/* Define a crash console for the plaform */
+#define FVP_CRASH_CONSOLE_BASE		PL011_UART0_BASE
+
+	/* ---------------------------------------------
+	 * int plat_crash_console_init(void)
+	 * Function to initialize the crash console
+	 * without a C Runtime to print crash report.
+	 * Clobber list : x0, x1, x2
+	 * ---------------------------------------------
+	 */
+func plat_crash_console_init
+	mov_imm	x0, FVP_CRASH_CONSOLE_BASE
+	mov_imm	x1, PL011_UART0_CLK_IN_HZ
+	mov_imm	x2, PL011_BAUDRATE
+	b	console_core_init
+
+	/* ---------------------------------------------
+	 * int plat_crash_console_putc(void)
+	 * Function to print a character on the crash
+	 * console without a C Runtime.
+	 * Clobber list : x1, x2
+	 * ---------------------------------------------
+	 */
+func plat_crash_console_putc
+	mov_imm	x1, FVP_CRASH_CONSOLE_BASE
+	b	console_core_putc