[PATCH v4 4/5] irqchip, gicv3-its: Add HW revision detection and configuration

[rric@kernel.org (Robert Richter)]

From: Robert Richter <rrichter@cavium.com>

Some GIC revisions require an individual configuration to esp. add
workarounds for HW bugs. This patch implements generic code to parse
the hw revision provided by an IIDR register value and runs specific
code if hw matches. There are functions that read the IIDR registers
for GICV3 and ITS (GICD_IIDR/GITS_IIDR) and then go through a list of
init functions to be called for specific versions.

A MIDR register value may also be used, this is especially useful for
hw detection from a guest.

The patch is needed to implement workarounds for HW errata in Cavium's
ThunderX GICV3.

v4:
 * only enable hw detection for its in its_enable_quirks()
 * removed gicv3_check_capabilities()

v3:
 * use arm64 errata framework for midr check

v2:
 * adding MIDR check

Signed-off-by: Robert Richter <rrichter@cavium.com>
---
 drivers/irqchip/irq-gic-common.c | 11 +++++++++++
 drivers/irqchip/irq-gic-common.h |  9 +++++++++
 drivers/irqchip/irq-gic-v3-its.c | 15 +++++++++++++++
 3 files changed, 35 insertions(+)

diff --git a/drivers/irqchip/irq-gic-common.c b/drivers/irqchip/irq-gic-common.c
index 9448e391cb71..ee789b07f2d1 100644
--- a/drivers/irqchip/irq-gic-common.c
+++ b/drivers/irqchip/irq-gic-common.c
@@ -21,6 +21,17 @@
 
 #include "irq-gic-common.h"
 
+void gic_check_capabilities(u32 iidr, const struct gic_capabilities *cap,
+			void *data)
+{
+	for (; cap->desc; cap++) {
+		if (cap->iidr != (cap->mask & iidr))
+			continue;
+		cap->init(data);
+		pr_info("%s\n", cap->desc);
+	}
+}
+
 int gic_configure_irq(unsigned int irq, unsigned int type,
 		       void __iomem *base, void (*sync_access)(void))
 {
diff --git a/drivers/irqchip/irq-gic-common.h b/drivers/irqchip/irq-gic-common.h
index 35a9884778bd..ca12635bbe3c 100644
--- a/drivers/irqchip/irq-gic-common.h
+++ b/drivers/irqchip/irq-gic-common.h
@@ -20,10 +20,19 @@
 #include <linux/of.h>
 #include <linux/irqdomain.h>
 
+struct gic_capabilities {
+	const char *desc;
+	void (*init)(void *data);
+	u32 iidr;
+	u32 mask;
+};
+
 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));
 void gic_cpu_config(void __iomem *base, void (*sync_access)(void));
+void gic_check_capabilities(u32 iidr, const struct gic_capabilities *cap,
+			void *data);
 
 #endif /* _IRQ_GIC_COMMON_H */
diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 06131db7a198..697421e834ee 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -36,6 +36,7 @@
 #include <asm/cputype.h>
 #include <asm/exception.h>
 
+#include "irq-gic-common.h"
 #include "irqchip.h"
 
 #define ITS_FLAGS_CMDQ_NEEDS_FLUSHING		(1 << 0)
@@ -1390,6 +1391,18 @@ static int its_force_quiescent(void __iomem *base)
 	}
 }
 
+static const struct gic_capabilities its_errata[] = {
+	{
+	}
+};
+
+static void its_enable_quirks(struct its_node *its)
+{
+	u32 iidr = readl_relaxed(its->base + GITS_IIDR);
+
+	gic_check_capabilities(iidr, its_errata, its);
+}
+
 static int its_probe(struct device_node *node, struct irq_domain *parent)
 {
 	struct resource res;
@@ -1448,6 +1461,8 @@ static int its_probe(struct device_node *node, struct irq_domain *parent)
 	}
 	its->cmd_write = its->cmd_base;
 
+	its_enable_quirks(its);
+
 	err = its_alloc_tables(its);
 	if (err)
 		goto out_free_cmd;
-- 
2.1.1