ARM: 7523/1: arch_timers: enable the use of the virtual timer

At the moment, the arch_timer driver only uses the physical timer,
which can cause problem if PL2 hasn't enabled PL1 access in CNTHCTL,
which is likely in a virtualized environment. Instead, the virtual
timer is always available.

This patch enables the use of the virtual timer, unless no
interrupt is provided in the DT for it, in which case it falls
back to the physical timer.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/arch_timer.c

@@ -27,13 +27,23 @@
 #include <asm/sched_clock.h>
 
 static unsigned long arch_timer_rate;
-static int arch_timer_ppi;
-static int arch_timer_ppi2;
+
+enum ppi_nr {
+	PHYS_SECURE_PPI,
+	PHYS_NONSECURE_PPI,
+	VIRT_PPI,
+	HYP_PPI,
+	MAX_TIMER_PPI
+};
+
+static int arch_timer_ppi[MAX_TIMER_PPI];
 
 static struct clock_event_device __percpu **arch_timer_evt;
 
 extern void init_current_timer_delay(unsigned long freq);
 
+static bool arch_timer_use_virtual = true;
+
 /*
  * Architected system timer support.
  */
@@ -46,8 +56,17 @@ extern void init_current_timer_delay(unsigned long freq);
 #define ARCH_TIMER_REG_FREQ		1
 #define ARCH_TIMER_REG_TVAL		2
 
-static void arch_timer_reg_write(int reg, u32 val)
+#define ARCH_TIMER_PHYS_ACCESS		0
+#define ARCH_TIMER_VIRT_ACCESS		1
+
+/*
+ * These register accessors are marked inline so the compiler can
+ * nicely work out which register we want, and chuck away the rest of
+ * the code. At least it does so with a recent GCC (4.6.3).
+ */
+static inline void arch_timer_reg_write(const int access, const int reg, u32 val)
 {
+	if (access == ARCH_TIMER_PHYS_ACCESS) {
 		switch (reg) {
 		case ARCH_TIMER_REG_CTRL:
 			asm volatile("mcr p15, 0, %0, c14, c2, 1" : : "r" (val));
@@ -56,40 +75,85 @@ static void arch_timer_reg_write(int reg, u32 val)
 			asm volatile("mcr p15, 0, %0, c14, c2, 0" : : "r" (val));
 			break;
 		}
+	}
+
+	if (access == ARCH_TIMER_VIRT_ACCESS) {
+		switch (reg) {
+		case ARCH_TIMER_REG_CTRL:
+			asm volatile("mcr p15, 0, %0, c14, c3, 1" : : "r" (val));
+			break;
+		case ARCH_TIMER_REG_TVAL:
+			asm volatile("mcr p15, 0, %0, c14, c3, 0" : : "r" (val));
+			break;
+		}
+	}
 
 	isb();
 }
 
-static u32 arch_timer_reg_read(int reg)
+static inline u32 arch_timer_reg_read(const int access, const int reg)
 {
-	u32 val;
+	u32 val = 0;
 
+	if (access == ARCH_TIMER_PHYS_ACCESS) {
 		switch (reg) {
 		case ARCH_TIMER_REG_CTRL:
 			asm volatile("mrc p15, 0, %0, c14, c2, 1" : "=r" (val));
 			break;
+		case ARCH_TIMER_REG_TVAL:
+			asm volatile("mrc p15, 0, %0, c14, c2, 0" : "=r" (val));
+			break;
 		case ARCH_TIMER_REG_FREQ:
 			asm volatile("mrc p15, 0, %0, c14, c0, 0" : "=r" (val));
 			break;
+		}
+	}
+
+	if (access == ARCH_TIMER_VIRT_ACCESS) {
+		switch (reg) {
+		case ARCH_TIMER_REG_CTRL:
+			asm volatile("mrc p15, 0, %0, c14, c3, 1" : "=r" (val));
+			break;
 		case ARCH_TIMER_REG_TVAL:
-		asm volatile("mrc p15, 0, %0, c14, c2, 0" : "=r" (val));
+			asm volatile("mrc p15, 0, %0, c14, c3, 0" : "=r" (val));
 			break;
-	default:
-		BUG();
+		}
 	}
 
 	return val;
 }
 
-static irqreturn_t arch_timer_handler(int irq, void *dev_id)
+static inline cycle_t arch_timer_counter_read(const int access)
 {
-	struct clock_event_device *evt = *(struct clock_event_device **)dev_id;
-	unsigned long ctrl;
+	cycle_t cval = 0;
 
-	ctrl = arch_timer_reg_read(ARCH_TIMER_REG_CTRL);
+	if (access == ARCH_TIMER_PHYS_ACCESS)
+		asm volatile("mrrc p15, 0, %Q0, %R0, c14" : "=r" (cval));
+
+	if (access == ARCH_TIMER_VIRT_ACCESS)
+		asm volatile("mrrc p15, 1, %Q0, %R0, c14" : "=r" (cval));
+
+	return cval;
+}
+
+static inline cycle_t arch_counter_get_cntpct(void)
+{
+	return arch_timer_counter_read(ARCH_TIMER_PHYS_ACCESS);
+}
+
+static inline cycle_t arch_counter_get_cntvct(void)
+{
+	return arch_timer_counter_read(ARCH_TIMER_VIRT_ACCESS);
+}
+
+static irqreturn_t inline timer_handler(const int access,
+					struct clock_event_device *evt)
+{
+	unsigned long ctrl;
+	ctrl = arch_timer_reg_read(access, ARCH_TIMER_REG_CTRL);
 	if (ctrl & ARCH_TIMER_CTRL_IT_STAT) {
 		ctrl |= ARCH_TIMER_CTRL_IT_MASK;
-		arch_timer_reg_write(ARCH_TIMER_REG_CTRL, ctrl);
+		arch_timer_reg_write(access, ARCH_TIMER_REG_CTRL, ctrl);
 		evt->event_handler(evt);
 		return IRQ_HANDLED;
 	}
@@ -97,63 +161,100 @@ static irqreturn_t arch_timer_handler(int irq, void *dev_id)
 	return IRQ_NONE;
 }
 
-static void arch_timer_disable(void)
+static irqreturn_t arch_timer_handler_virt(int irq, void *dev_id)
 {
-	unsigned long ctrl;
+	struct clock_event_device *evt = *(struct clock_event_device **)dev_id;
 
-	ctrl = arch_timer_reg_read(ARCH_TIMER_REG_CTRL);
-	ctrl &= ~ARCH_TIMER_CTRL_ENABLE;
-	arch_timer_reg_write(ARCH_TIMER_REG_CTRL, ctrl);
+	return timer_handler(ARCH_TIMER_VIRT_ACCESS, evt);
 }
 
-static void arch_timer_set_mode(enum clock_event_mode mode,
-				struct clock_event_device *clk)
+static irqreturn_t arch_timer_handler_phys(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = *(struct clock_event_device **)dev_id;
+
+	return timer_handler(ARCH_TIMER_PHYS_ACCESS, evt);
+}
+
+static inline void timer_set_mode(const int access, int mode)
 {
+	unsigned long ctrl;
 	switch (mode) {
 	case CLOCK_EVT_MODE_UNUSED:
 	case CLOCK_EVT_MODE_SHUTDOWN:
-		arch_timer_disable();
+		ctrl = arch_timer_reg_read(access, ARCH_TIMER_REG_CTRL);
+		ctrl &= ~ARCH_TIMER_CTRL_ENABLE;
+		arch_timer_reg_write(access, ARCH_TIMER_REG_CTRL, ctrl);
 		break;
 	default:
 		break;
 	}
 }
 
-static int arch_timer_set_next_event(unsigned long evt,
-				     struct clock_event_device *unused)
+static void arch_timer_set_mode_virt(enum clock_event_mode mode,
+				     struct clock_event_device *clk)
 {
-	unsigned long ctrl;
+	timer_set_mode(ARCH_TIMER_VIRT_ACCESS, mode);
+}
 
-	ctrl = arch_timer_reg_read(ARCH_TIMER_REG_CTRL);
+static void arch_timer_set_mode_phys(enum clock_event_mode mode,
+				     struct clock_event_device *clk)
+{
+	timer_set_mode(ARCH_TIMER_PHYS_ACCESS, mode);
+}
+
+static inline void set_next_event(const int access, unsigned long evt)
+{
+	unsigned long ctrl;
+	ctrl = arch_timer_reg_read(access, ARCH_TIMER_REG_CTRL);
 	ctrl |= ARCH_TIMER_CTRL_ENABLE;
 	ctrl &= ~ARCH_TIMER_CTRL_IT_MASK;
+	arch_timer_reg_write(access, ARCH_TIMER_REG_TVAL, evt);
+	arch_timer_reg_write(access, ARCH_TIMER_REG_CTRL, ctrl);
+}
 
-	arch_timer_reg_write(ARCH_TIMER_REG_TVAL, evt);
-	arch_timer_reg_write(ARCH_TIMER_REG_CTRL, ctrl);
+static int arch_timer_set_next_event_virt(unsigned long evt,
+					  struct clock_event_device *unused)
+{
+	set_next_event(ARCH_TIMER_VIRT_ACCESS, evt);
+	return 0;
+}
 
+static int arch_timer_set_next_event_phys(unsigned long evt,
+					  struct clock_event_device *unused)
+{
+	set_next_event(ARCH_TIMER_PHYS_ACCESS, evt);
 	return 0;
 }
 
 static int __cpuinit arch_timer_setup(struct clock_event_device *clk)
 {
-	/* Be safe... */
-	arch_timer_disable();
-
 	clk->features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP;
 	clk->name = "arch_sys_timer";
 	clk->rating = 450;
-	clk->set_mode = arch_timer_set_mode;
-	clk->set_next_event = arch_timer_set_next_event;
-	clk->irq = arch_timer_ppi;
+	if (arch_timer_use_virtual) {
+		clk->irq = arch_timer_ppi[VIRT_PPI];
+		clk->set_mode = arch_timer_set_mode_virt;
+		clk->set_next_event = arch_timer_set_next_event_virt;
+	} else {
+		clk->irq = arch_timer_ppi[PHYS_SECURE_PPI];
+		clk->set_mode = arch_timer_set_mode_phys;
+		clk->set_next_event = arch_timer_set_next_event_phys;
+	}
+
+	clk->set_mode(CLOCK_EVT_MODE_SHUTDOWN, NULL);
 
 	clockevents_config_and_register(clk, arch_timer_rate,
 					0xf, 0x7fffffff);
 
 	*__this_cpu_ptr(arch_timer_evt) = clk;
 
-	enable_percpu_irq(clk->irq, 0);
-	if (arch_timer_ppi2)
-		enable_percpu_irq(arch_timer_ppi2, 0);
+	if (arch_timer_use_virtual)
+		enable_percpu_irq(arch_timer_ppi[VIRT_PPI], 0);
+	else {
+		enable_percpu_irq(arch_timer_ppi[PHYS_SECURE_PPI], 0);
+		if (arch_timer_ppi[PHYS_NONSECURE_PPI])
+			enable_percpu_irq(arch_timer_ppi[PHYS_NONSECURE_PPI], 0);
+	}
 
 	return 0;
 }
@@ -173,8 +274,8 @@ static int arch_timer_available(void)
 		return -ENXIO;
 
 	if (arch_timer_rate == 0) {
-		arch_timer_reg_write(ARCH_TIMER_REG_CTRL, 0);
-		freq = arch_timer_reg_read(ARCH_TIMER_REG_FREQ);
+		freq = arch_timer_reg_read(ARCH_TIMER_PHYS_ACCESS,
+					   ARCH_TIMER_REG_FREQ);
 
 		/* Check the timer frequency. */
 		if (freq == 0) {
@@ -185,43 +286,42 @@ static int arch_timer_available(void)
 		arch_timer_rate = freq;
 	}
 
-	pr_info_once("Architected local timer running at %lu.%02luMHz.\n",
-		     arch_timer_rate / 1000000, (arch_timer_rate / 10000) % 100);
+	pr_info_once("Architected local timer running at %lu.%02luMHz (%s).\n",
+		     arch_timer_rate / 1000000, (arch_timer_rate / 10000) % 100,
+		     arch_timer_use_virtual ? "virt" : "phys");
 	return 0;
 }
 
-static inline cycle_t arch_counter_get_cntpct(void)
-{
-	u32 cvall, cvalh;
-
-	asm volatile("mrrc p15, 0, %0, %1, c14" : "=r" (cvall), "=r" (cvalh));
-
-	return ((cycle_t) cvalh << 32) | cvall;
-}
-
-static inline cycle_t arch_counter_get_cntvct(void)
+static u32 notrace arch_counter_get_cntpct32(void)
 {
-	u32 cvall, cvalh;
+	cycle_t cnt = arch_counter_get_cntpct();
 
-	asm volatile("mrrc p15, 1, %0, %1, c14" : "=r" (cvall), "=r" (cvalh));
-
-	return ((cycle_t) cvalh << 32) | cvall;
+	/*
+	 * The sched_clock infrastructure only knows about counters
+	 * with at most 32bits. Forget about the upper 24 bits for the
+	 * time being...
+	 */
+	return (u32)cnt;
 }
 
 static u32 notrace arch_counter_get_cntvct32(void)
 {
-	cycle_t cntvct = arch_counter_get_cntvct();
+	cycle_t cnt = arch_counter_get_cntvct();
 
 	/*
 	 * The sched_clock infrastructure only knows about counters
 	 * with at most 32bits. Forget about the upper 24 bits for the
 	 * time being...
 	 */
-	return (u32)(cntvct & (u32)~0);
+	return (u32)cnt;
 }
 
 static cycle_t arch_counter_read(struct clocksource *cs)
 {
+	/*
+	 * Always use the physical counter for the clocksource.
+	 * CNTHCTL.PL1PCTEN must be set to 1.
+	 */
 	return arch_counter_get_cntpct();
 }
 
@@ -245,10 +345,16 @@ static void __cpuinit arch_timer_stop(struct clock_event_device *clk)
 {
 	pr_debug("arch_timer_teardown disable IRQ%d cpu #%d\n",
 		 clk->irq, smp_processor_id());
-	disable_percpu_irq(clk->irq);
-	if (arch_timer_ppi2)
-		disable_percpu_irq(arch_timer_ppi2);
-	arch_timer_set_mode(CLOCK_EVT_MODE_UNUSED, clk);
+
+	if (arch_timer_use_virtual)
+		disable_percpu_irq(arch_timer_ppi[VIRT_PPI]);
+	else {
+		disable_percpu_irq(arch_timer_ppi[PHYS_SECURE_PPI]);
+		if (arch_timer_ppi[PHYS_NONSECURE_PPI])
+			disable_percpu_irq(arch_timer_ppi[PHYS_NONSECURE_PPI]);
+	}
+
+	clk->set_mode(CLOCK_EVT_MODE_UNUSED, clk);
 }
 
 static struct local_timer_ops arch_timer_ops __cpuinitdata = {
@@ -261,34 +367,42 @@ static struct clock_event_device arch_timer_global_evt;
 static int __init arch_timer_register(void)
 {
 	int err;
+	int ppi;
 
 	err = arch_timer_available();
 	if (err)
-		return err;
+		goto out;
 
 	arch_timer_evt = alloc_percpu(struct clock_event_device *);
-	if (!arch_timer_evt)
-		return -ENOMEM;
+	if (!arch_timer_evt) {
+		err = -ENOMEM;
+		goto out;
+	}
 
 	clocksource_register_hz(&clocksource_counter, arch_timer_rate);
 
-	err = request_percpu_irq(arch_timer_ppi, arch_timer_handler,
+	if (arch_timer_use_virtual) {
+		ppi = arch_timer_ppi[VIRT_PPI];
+		err = request_percpu_irq(ppi, arch_timer_handler_virt,
 					 "arch_timer", arch_timer_evt);
-	if (err) {
-		pr_err("arch_timer: can't register interrupt %d (%d)\n",
-		       arch_timer_ppi, err);
-		goto out_free;
+	} else {
+		ppi = arch_timer_ppi[PHYS_SECURE_PPI];
+		err = request_percpu_irq(ppi, arch_timer_handler_phys,
+					 "arch_timer", arch_timer_evt);
+		if (!err && arch_timer_ppi[PHYS_NONSECURE_PPI]) {
+			ppi = arch_timer_ppi[PHYS_NONSECURE_PPI];
+			err = request_percpu_irq(ppi, arch_timer_handler_phys,
+						 "arch_timer", arch_timer_evt);
+			if (err)
+				free_percpu_irq(arch_timer_ppi[PHYS_SECURE_PPI],
+						arch_timer_evt);
+		}
 	}
 
-	if (arch_timer_ppi2) {
-		err = request_percpu_irq(arch_timer_ppi2, arch_timer_handler,
-					 "arch_timer", arch_timer_evt);
 	if (err) {
 		pr_err("arch_timer: can't register interrupt %d (%d)\n",
-			       arch_timer_ppi2, err);
-			arch_timer_ppi2 = 0;
-			goto out_free_irq;
-		}
+		       ppi, err);
+		goto out_free;
 	}
 
 	err = local_timer_register(&arch_timer_ops);
@@ -310,13 +424,19 @@ static int __init arch_timer_register(void)
 	return 0;
 
 out_free_irq:
-	free_percpu_irq(arch_timer_ppi, arch_timer_evt);
-	if (arch_timer_ppi2)
-		free_percpu_irq(arch_timer_ppi2, arch_timer_evt);
+	if (arch_timer_use_virtual)
+		free_percpu_irq(arch_timer_ppi[VIRT_PPI], arch_timer_evt);
+	else {
+		free_percpu_irq(arch_timer_ppi[PHYS_SECURE_PPI],
+				arch_timer_evt);
+		if (arch_timer_ppi[PHYS_NONSECURE_PPI])
+			free_percpu_irq(arch_timer_ppi[PHYS_NONSECURE_PPI],
+					arch_timer_evt);
+	}
 
 out_free:
 	free_percpu(arch_timer_evt);
-
+out:
 	return err;
 }
 
@@ -329,6 +449,7 @@ int __init arch_timer_of_register(void)
 {
 	struct device_node *np;
 	u32 freq;
+	int i;
 
 	np = of_find_matching_node(NULL, arch_timer_of_match);
 	if (!np) {
@@ -340,22 +461,40 @@ int __init arch_timer_of_register(void)
 	if (!of_property_read_u32(np, "clock-frequency", &freq))
 		arch_timer_rate = freq;
 
-	arch_timer_ppi = irq_of_parse_and_map(np, 0);
-	arch_timer_ppi2 = irq_of_parse_and_map(np, 1);
-	pr_info("arch_timer: found %s irqs %d %d\n",
-		np->name, arch_timer_ppi, arch_timer_ppi2);
+	for (i = PHYS_SECURE_PPI; i < MAX_TIMER_PPI; i++)
+		arch_timer_ppi[i] = irq_of_parse_and_map(np, i);
+
+	/*
+	 * If no interrupt provided for virtual timer, we'll have to
+	 * stick to the physical timer. It'd better be accessible...
+	 */
+	if (!arch_timer_ppi[VIRT_PPI]) {
+		arch_timer_use_virtual = false;
+
+		if (!arch_timer_ppi[PHYS_SECURE_PPI] ||
+		    !arch_timer_ppi[PHYS_NONSECURE_PPI]) {
+			pr_warn("arch_timer: No interrupt available, giving up\n");
+			return -EINVAL;
+		}
+	}
 
 	return arch_timer_register();
 }
 
 int __init arch_timer_sched_clock_init(void)
 {
+	u32 (*cnt32)(void);
 	int err;
 
 	err = arch_timer_available();
 	if (err)
 		return err;
 
-	setup_sched_clock(arch_counter_get_cntvct32, 32, arch_timer_rate);
+	if (arch_timer_use_virtual)
+		cnt32 = arch_counter_get_cntvct32;
+	else
+		cnt32 = arch_counter_get_cntpct32;
+
+	setup_sched_clock(cnt32, 32, arch_timer_rate);
 	return 0;
 }