irqchip: gic: Allow interrupt level to be set for PPIs

During a recent cleanup of the arm64 DTs it has become clear that
the handling of PPIs in xxxx_set_type() is incorrect. The ARM TRMs
for GICv2 and later allow for "implementation defined" support for
setting the edge or level type of the PPI interrupts and don't restrict
the activation level of the signal. Current ARM implementations
do restrict the PPI level type to IRQ_TYPE_LEVEL_LOW, but licensees
of the IP can decide to shoot themselves in the foot at any time.

Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
Acked-by: Marc Zyngier <Marc.Zyngier@arm.com>
Cc: LAKML <linux-arm-kernel@lists.infradead.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Haojian Zhuang <haojian.zhuang@linaro.org>
Link: http://lkml.kernel.org/r/1421772779-25764-1-git-send-email-Liviu.Dudau@arm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Documentation/devicetree/bindings/arm/gic.txt

@@ -32,12 +32,16 @@ Main node required properties:
   The 3rd cell is the flags, encoded as follows:
 	bits[3:0] trigger type and level flags.
 		1 = low-to-high edge triggered
-		2 = high-to-low edge triggered
+		2 = high-to-low edge triggered (invalid for SPIs)
 		4 = active high level-sensitive
-		8 = active low level-sensitive
+		8 = active low level-sensitive (invalid for SPIs).
 	bits[15:8] PPI interrupt cpu mask.  Each bit corresponds to each of
 	the 8 possible cpus attached to the GIC.  A bit set to '1' indicated
 	the interrupt is wired to that CPU.  Only valid for PPI interrupts.
+	Also note that the configurability of PPI interrupts is IMPLEMENTATION
+	DEFINED and as such not guaranteed to be present (most SoC available
+	in 2014 seem to ignore the setting of this flag and use the hardware
+	default value).
 
 - reg : Specifies base physical address(s) and size of the GIC registers. The
   first region is the GIC distributor register base and size. The 2nd region is

drivers/irqchip/irq-gic-common.c

@@ -21,24 +21,25 @@
 
 #include "irq-gic-common.h"
 
-void gic_configure_irq(unsigned int irq, unsigned int type,
+int gic_configure_irq(unsigned int irq, unsigned int type,
 		       void __iomem *base, void (*sync_access)(void))
 {
 	u32 enablemask = 1 << (irq % 32);
 	u32 enableoff = (irq / 32) * 4;
 	u32 confmask = 0x2 << ((irq % 16) * 2);
 	u32 confoff = (irq / 16) * 4;
 	bool enabled = false;
-	u32 val;
+	u32 val, oldval;
+	int ret = 0;
 
 	/*
 	 * Read current configuration register, and insert the config
 	 * for "irq", depending on "type".
 	 */
-	val = readl_relaxed(base + GIC_DIST_CONFIG + confoff);
-	if (type == IRQ_TYPE_LEVEL_HIGH)
+	val = oldval = readl_relaxed(base + GIC_DIST_CONFIG + confoff);
+	if (type & IRQ_TYPE_LEVEL_MASK)
 		val &= ~confmask;
-	else if (type == IRQ_TYPE_EDGE_RISING)
+	else if (type & IRQ_TYPE_EDGE_BOTH)
 		val |= confmask;
 
 	/*
@@ -54,15 +55,20 @@ void gic_configure_irq(unsigned int irq, unsigned int type,
 
 	/*
 	 * Write back the new configuration, and possibly re-enable
-	 * the interrupt.
+	 * the interrupt. If we tried to write a new configuration and failed,
+	 * return an error.
 	 */
 	writel_relaxed(val, base + GIC_DIST_CONFIG + confoff);
+	if (readl_relaxed(base + GIC_DIST_CONFIG + confoff) != val && val != oldval)
+		ret = -EINVAL;
 
 	if (enabled)
 		writel_relaxed(enablemask, base + GIC_DIST_ENABLE_SET + enableoff);
 
 	if (sync_access)
 		sync_access();
+
+	return ret;
 }
 
 void __init gic_dist_config(void __iomem *base, int gic_irqs,

drivers/irqchip/irq-gic-common.h

@@ -20,7 +20,7 @@
 #include <linux/of.h>
 #include <linux/irqdomain.h>
 
-void gic_configure_irq(unsigned int irq, unsigned int type,
+int gic_configure_irq(unsigned int irq, unsigned int type,
                        void __iomem *base, void (*sync_access)(void));
 void gic_dist_config(void __iomem *base, int gic_irqs,
 		     void (*sync_access)(void));

drivers/irqchip/irq-gic-v3.c

@@ -238,7 +238,9 @@ static int gic_set_type(struct irq_data *d, unsigned int type)
 	if (irq < 16)
 		return -EINVAL;
 
-	if (type != IRQ_TYPE_LEVEL_HIGH && type != IRQ_TYPE_EDGE_RISING)
+	/* SPIs have restrictions on the supported types */
+	if (irq >= 32 && type != IRQ_TYPE_LEVEL_HIGH &&
+			 type != IRQ_TYPE_EDGE_RISING)
 		return -EINVAL;
 
 	if (gic_irq_in_rdist(d)) {
@@ -249,9 +251,7 @@ static int gic_set_type(struct irq_data *d, unsigned int type)
 		rwp_wait = gic_dist_wait_for_rwp;
 	}
 
-	gic_configure_irq(irq, type, base, rwp_wait);
-
-	return 0;
+	return gic_configure_irq(irq, type, base, rwp_wait);
 }
 
 static u64 gic_mpidr_to_affinity(u64 mpidr)

drivers/irqchip/irq-gic.c

@@ -188,24 +188,27 @@ static int gic_set_type(struct irq_data *d, unsigned int type)
 {
 	void __iomem *base = gic_dist_base(d);
 	unsigned int gicirq = gic_irq(d);
+	int ret;
 
 	/* Interrupt configuration for SGIs can't be changed */
 	if (gicirq < 16)
 		return -EINVAL;
 
-	if (type != IRQ_TYPE_LEVEL_HIGH && type != IRQ_TYPE_EDGE_RISING)
+	/* SPIs have restrictions on the supported types */
+	if (gicirq >= 32 && type != IRQ_TYPE_LEVEL_HIGH &&
+			    type != IRQ_TYPE_EDGE_RISING)
 		return -EINVAL;
 
 	raw_spin_lock(&irq_controller_lock);
 
 	if (gic_arch_extn.irq_set_type)
 		gic_arch_extn.irq_set_type(d, type);
 
-	gic_configure_irq(gicirq, type, base, NULL);
+	ret = gic_configure_irq(gicirq, type, base, NULL);
 
 	raw_spin_unlock(&irq_controller_lock);
 
-	return 0;
+	return ret;
 }
 
 static int gic_retrigger(struct irq_data *d)

drivers/irqchip/irq-hip04.c

@@ -120,21 +120,24 @@ static int hip04_irq_set_type(struct irq_data *d, unsigned int type)
 {
 	void __iomem *base = hip04_dist_base(d);
 	unsigned int irq = hip04_irq(d);
+	int ret;
 
 	/* Interrupt configuration for SGIs can't be changed */
 	if (irq < 16)
 		return -EINVAL;
 
-	if (type != IRQ_TYPE_LEVEL_HIGH && type != IRQ_TYPE_EDGE_RISING)
+	/* SPIs have restrictions on the supported types */
+	if (irq >= 32 && type != IRQ_TYPE_LEVEL_HIGH &&
+			 type != IRQ_TYPE_EDGE_RISING)
 		return -EINVAL;
 
 	raw_spin_lock(&irq_controller_lock);
 
-	gic_configure_irq(irq, type, base, NULL);
+	ret = gic_configure_irq(irq, type, base, NULL);
 
 	raw_spin_unlock(&irq_controller_lock);
 
-	return 0;
+	return ret;
 }
 
 #ifdef CONFIG_SMP