Tegra: implement FIQ interrupt handler

This patch adds a handler for FIQ interrupts triggered when
the CPU is in the NS world. The handler stores the NS world's
context along with ELR_EL3/SPSR_EL3.

The NS world driver issues an SMC initially to register it's
handler. The monitor firmware stores this handler address and
jumps to it when the FIQ interrupt fires. Upon entry into the
NS world the driver then issues another SMC to get the CPU
context when the FIQ fired. This allows the NS world driver to
determine the CPU state and call stack when the interrupt
fired. Generally, systems register watchdog interrupts as FIQs
which are then used to get the CPU state during hangs/crashes.

Change-Id: I733af61a08d1318c75acedbe9569a758744edd0c
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>

plat/nvidia/tegra/common/tegra_common.mk

@@ -55,6 +55,7 @@ BL31_SOURCES		+=	drivers/arm/gic/gic_v2.c			\
 				${COMMON_DIR}/drivers/pmc/pmc.c			\
 				${COMMON_DIR}/tegra_bl31_setup.c		\
 				${COMMON_DIR}/tegra_delay_timer.c		\
+				${COMMON_DIR}/tegra_fiq_glue.c			\
 				${COMMON_DIR}/tegra_gic.c			\
 				${COMMON_DIR}/tegra_pm.c			\
 				${COMMON_DIR}/tegra_sip_calls.c			\

plat/nvidia/tegra/common/tegra_fiq_glue.c

+/*
+ * Copyright (c) 2016, ARM Limited and Contributors. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * Neither the name of ARM nor the names of its contributors may be used
+ * to endorse or promote products derived from this software without specific
+ * prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <arch_helpers.h>
+#include <assert.h>
+#include <bakery_lock.h>
+#include <bl_common.h>
+#include <context.h>
+#include <context_mgmt.h>
+#include <debug.h>
+#include <denver.h>
+#include <gic_v2.h>
+#include <interrupt_mgmt.h>
+#include <platform.h>
+#include <tegra_def.h>
+#include <tegra_private.h>
+
+DEFINE_BAKERY_LOCK(tegra_fiq_lock);
+
+/*******************************************************************************
+ * Static variables
+ ******************************************************************************/
+static uint64_t ns_fiq_handler_addr;
+static unsigned int fiq_handler_active;
+static pcpu_fiq_state_t fiq_state[PLATFORM_CORE_COUNT];
+
+/*******************************************************************************
+ * Handler for FIQ interrupts
+ ******************************************************************************/
+static uint64_t tegra_fiq_interrupt_handler(uint32_t id,
+					  uint32_t flags,
+					  void *handle,
+					  void *cookie)
+{
+	cpu_context_t *ctx = cm_get_context(NON_SECURE);
+	el3_state_t *el3state_ctx = get_el3state_ctx(ctx);
+	int cpu = plat_my_core_pos();
+	uint32_t irq;
+
+	bakery_lock_get(&tegra_fiq_lock);
+
+	/*
+	 * The FIQ was generated when the execution was in the non-secure
+	 * world. Save the context registers to start with.
+	 */
+	cm_el1_sysregs_context_save(NON_SECURE);
+
+	/*
+	 * Save elr_el3 and spsr_el3 from the saved context, and overwrite
+	 * the context with the NS fiq_handler_addr and SPSR value.
+	 */
+	fiq_state[cpu].elr_el3 = read_ctx_reg(el3state_ctx, CTX_ELR_EL3);
+	fiq_state[cpu].spsr_el3 = read_ctx_reg(el3state_ctx, CTX_SPSR_EL3);
+
+	/*
+	 * Set the new ELR to continue execution in the NS world using the
+	 * FIQ handler registered earlier.
+	 */
+	assert(ns_fiq_handler_addr);
+	write_ctx_reg(el3state_ctx, CTX_ELR_EL3, ns_fiq_handler_addr);
+
+	/*
+	 * Mark this interrupt as complete to avoid a FIQ storm.
+	 */
+	irq = plat_ic_acknowledge_interrupt();
+	if (irq < 1022)
+		plat_ic_end_of_interrupt(irq);
+
+	bakery_lock_release(&tegra_fiq_lock);
+
+	return 0;
+}
+
+/*******************************************************************************
+ * Setup handler for FIQ interrupts
+ ******************************************************************************/
+void tegra_fiq_handler_setup(void)
+{
+	uint64_t flags;
+	int rc;
+
+	/* return if already registered */
+	if (fiq_handler_active)
+		return;
+
+	/*
+	 * Register an interrupt handler for FIQ interrupts generated for
+	 * NS interrupt sources
+	 */
+	flags = 0;
+	set_interrupt_rm_flag(flags, NON_SECURE);
+	rc = register_interrupt_type_handler(INTR_TYPE_S_EL1,
+				tegra_fiq_interrupt_handler,
+				flags);
+	if (rc)
+		panic();
+
+	/* handler is now active */
+	fiq_handler_active = 1;
+}
+
+/*******************************************************************************
+ * Validate and store NS world's entrypoint for FIQ interrupts
+ ******************************************************************************/
+void tegra_fiq_set_ns_entrypoint(uint64_t entrypoint)
+{
+	ns_fiq_handler_addr = entrypoint;
+}
+
+/*******************************************************************************
+ * Handler to return the NS EL1/EL0 CPU context
+ ******************************************************************************/
+int tegra_fiq_get_intr_context(void)
+{
+	cpu_context_t *ctx = cm_get_context(NON_SECURE);
+	gp_regs_t *gpregs_ctx = get_gpregs_ctx(ctx);
+	el1_sys_regs_t *el1state_ctx = get_sysregs_ctx(ctx);
+	int cpu = plat_my_core_pos();
+	uint64_t val;
+
+	/*
+	 * We store the ELR_EL3, SPSR_EL3, SP_EL0 and SP_EL1 registers so
+	 * that el3_exit() sends these values back to the NS world.
+	 */
+	write_ctx_reg(gpregs_ctx, CTX_GPREG_X0, fiq_state[cpu].elr_el3);
+	write_ctx_reg(gpregs_ctx, CTX_GPREG_X1, fiq_state[cpu].spsr_el3);
+
+	val = read_ctx_reg(gpregs_ctx, CTX_GPREG_SP_EL0);
+	write_ctx_reg(gpregs_ctx, CTX_GPREG_X2, val);
+
+	val = read_ctx_reg(el1state_ctx, CTX_SP_EL1);
+	write_ctx_reg(gpregs_ctx, CTX_GPREG_X3, val);
+
+	return 0;
+}

plat/nvidia/tegra/common/tegra_sip_calls.c

@@ -42,6 +42,8 @@
  * Common Tegra SiP SMCs
  ******************************************************************************/
 #define TEGRA_SIP_NEW_VIDEOMEM_REGION		0x82000003
+#define TEGRA_SIP_FIQ_NS_ENTRYPOINT		0x82000005
+#define TEGRA_SIP_FIQ_NS_GET_CONTEXT		0x82000006
 
 /*******************************************************************************
  * SoC specific SiP handler
@@ -108,6 +110,41 @@ uint64_t tegra_sip_handler(uint32_t smc_fid,
 		SMC_RET1(handle, 0);
 		break;
 
+	/*
+	 * The NS world registers the address of its handler to be
+	 * used for processing the FIQ. This is normally used by the
+	 * NS FIQ debugger driver to detect system hangs by programming
+	 * a watchdog timer to fire a FIQ interrupt.
+	 */
+	case TEGRA_SIP_FIQ_NS_ENTRYPOINT:
+
+		if (!x1)
+			SMC_RET1(handle, SMC_UNK);
+
+		/*
+		 * TODO: Check if x1 contains a valid DRAM address
+		 */
+
+		/* store the NS world's entrypoint */
+		tegra_fiq_set_ns_entrypoint(x1);
+
+		SMC_RET1(handle, 0);
+		break;
+
+	/*
+	 * The NS world's FIQ handler issues this SMC to get the NS EL1/EL0
+	 * CPU context when the FIQ interrupt was triggered. This allows the
+	 * NS world to understand the CPU state when the watchdog interrupt
+	 * triggered.
+	 */
+	case TEGRA_SIP_FIQ_NS_GET_CONTEXT:
+
+		/* retrieve context registers when FIQ triggered */
+		tegra_fiq_get_intr_context();
+
+		SMC_RET0(handle);
+		break;
+
 	default:
 		ERROR("%s: unhandled SMC (0x%x)\n", __func__, smc_fid);
 		break;

plat/nvidia/tegra/include/tegra_private.h

@@ -54,6 +54,14 @@ typedef struct plat_params_from_bl2 {
 	int uart_id;
 } plat_params_from_bl2_t;
 
+/*******************************************************************************
+ * Per-CPU struct describing FIQ state to be stored
+ ******************************************************************************/
+typedef struct pcpu_fiq_state {
+	uint64_t elr_el3;
+	uint64_t spsr_el3;
+} pcpu_fiq_state_t;
+
 /* Declarations for plat_psci_handlers.c */
 int32_t tegra_soc_validate_power_state(unsigned int power_state,
 		psci_power_state_t *req_state);
@@ -67,6 +75,11 @@ void plat_gic_setup(void);
 void plat_secondary_setup(void);
 int plat_lock_cpu_vectors(void);
 
+/* Declarations for tegra_fiq_glue.c */
+void tegra_fiq_handler_setup(void);
+int tegra_fiq_get_intr_context(void);
+void tegra_fiq_set_ns_entrypoint(uint64_t entrypoint);
+
 /* Declarations for tegra_gic.c */
 void tegra_gic_setup(const unsigned int *irq_sec_ptr, unsigned int num_irqs);
 void tegra_gic_cpuif_deactivate(void);