[PATCH ARM v6 12/14] mini-os: arm: interrupt controller

[Thomas Leonard <talex5@gmail.com>]

Based on an initial patch by Karim Raslan.

Signed-off-by: Karim Allah Ahmed <karim.allah.ahmed@gmail.com>
Signed-off-by: Thomas Leonard <talex5@gmail.com>

---

Changes since v5:

Addressed Julien Grall's comments:
- Added comments explaining the lengths when checking FDT properties.
- Fixed (commented) DEBUG macro.
- Drop check for arm,cortex-a9-gic.

- Require only minimum property lengths (requested by Ian Campbell).
---
 extras/mini-os/arch/arm/gic.c | 232 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 232 insertions(+)
 create mode 100644 extras/mini-os/arch/arm/gic.c

diff --git a/extras/mini-os/arch/arm/gic.c b/extras/mini-os/arch/arm/gic.c
new file mode 100644
index 0000000..1afa099
--- /dev/null
+++ b/extras/mini-os/arch/arm/gic.c
@@ -0,0 +1,232 @@
+// ARM GIC implementation
+
+#include <mini-os/os.h>
+#include <mini-os/hypervisor.h>
+#include <mini-os/console.h>
+#include <libfdt.h>
+
+//#define VGIC_DEBUG
+#ifdef VGIC_DEBUG
+#define DEBUG(_f, _a...) \
+    printk("MINI_OS(file=vgic.c, line=%d) " _f , __LINE__, ## _a)
+#else
+#define DEBUG(_f, _a...)    ((void)0)
+#endif
+
+extern void (*IRQ_handler)(void);
+
+struct gic {
+    volatile char *gicd_base;
+    volatile char *gicc_base;
+};
+
+static struct gic gic;
+
+// Distributor Interface
+#define GICD_CTLR        0x0
+#define GICD_ISENABLER    0x100
+#define GICD_IPRIORITYR   0x400
+#define GICD_ITARGETSR    0x800
+#define GICD_ICFGR        0xC00
+
+// CPU Interface
+#define GICC_CTLR    0x0
+#define GICC_PMR    0x4
+#define GICC_IAR    0xc
+#define GICC_EOIR    0x10
+#define GICC_HPPIR    0x18
+
+#define gicd(gic, offset) ((gic)->gicd_base + (offset))
+#define gicc(gic, offset) ((gic)->gicc_base + (offset))
+
+#define REG(addr) ((uint32_t *)(addr))
+
+static inline uint32_t REG_READ32(volatile uint32_t *addr)
+{
+    uint32_t value;
+    __asm__ __volatile__("ldr %0, [%1]":"=&r"(value):"r"(addr));
+    rmb();
+    return value;
+}
+
+static inline void REG_WRITE32(volatile uint32_t *addr, unsigned int value)
+{
+    __asm__ __volatile__("str %0, [%1]"::"r"(value), "r"(addr));
+    wmb();
+}
+
+static void gic_set_priority(struct gic *gic, int irq_number, unsigned char priority)
+{
+    uint32_t value;
+    uint32_t *addr = REG(gicd(gic, GICD_IPRIORITYR)) + (irq_number >> 2);
+    value = REG_READ32(addr);
+    value &= ~(0xff << (8 * (irq_number & 0x3))); // clear old priority
+    value |= priority << (8 * (irq_number & 0x3)); // set new priority
+    REG_WRITE32(addr, value);
+}
+
+static void gic_route_interrupt(struct gic *gic, int irq_number, unsigned char cpu_set)
+{
+    uint32_t value;
+    uint32_t *addr = REG(gicd(gic, GICD_ITARGETSR)) + (irq_number >> 2);
+    value = REG_READ32(addr);
+    value &= ~(0xff << (8 * (irq_number & 0x3))); // clear old target
+    value |= cpu_set << (8 * (irq_number & 0x3)); // set new target
+    REG_WRITE32(addr, value);
+}
+
+/* When accessing the GIC registers, we can't use LDREX/STREX because it's not regular memory. */
+static __inline__ void clear_bit_non_atomic(int nr, volatile void *base)
+{
+    volatile uint32_t *tmp = base;
+    tmp[nr >> 5] &= (unsigned long)~(1 << (nr & 0x1f));
+}
+
+static __inline__ void set_bit_non_atomic(int nr, volatile void *base)
+{
+    volatile uint32_t *tmp = base;
+    tmp[nr >> 5] |= (1 << (nr & 0x1f));
+}
+
+/* Note: not thread safe (but we only support one CPU for now anyway) */
+static void gic_enable_interrupt(struct gic *gic, int irq_number,
+        unsigned char cpu_set, unsigned char level_sensitive, unsigned char ppi)
+{
+    void *set_enable_reg;
+    void *cfg_reg;
+
+    // set priority
+    gic_set_priority(gic, irq_number, 0x0);
+
+    // set target cpus for this interrupt
+    gic_route_interrupt(gic, irq_number, cpu_set);
+
+    // set level/edge triggered
+    cfg_reg = (void *)gicd(gic, GICD_ICFGR);
+    level_sensitive ? clear_bit_non_atomic((irq_number * 2) + 1, cfg_reg) : set_bit_non_atomic((irq_number * 2) + 1, cfg_reg);
+    if(ppi)
+        clear_bit_non_atomic((irq_number * 2), cfg_reg);
+
+    wmb();
+
+    // enable forwarding interrupt from distributor to cpu interface
+    set_enable_reg = (void *)gicd(gic, GICD_ISENABLER);
+    set_bit_non_atomic(irq_number, set_enable_reg);
+    wmb();
+}
+
+static void gic_enable_interrupts(struct gic *gic)
+{
+    // Global enable forwarding interrupts from distributor to cpu interface
+    REG_WRITE32(REG(gicd(gic, GICD_CTLR)), 0x00000001);
+
+    // Global enable signalling of interrupt from the cpu interface
+    REG_WRITE32(REG(gicc(gic, GICC_CTLR)), 0x00000001);
+}
+
+static void gic_disable_interrupts(struct gic *gic)
+{
+    // Global disable signalling of interrupt from the cpu interface
+    REG_WRITE32(REG(gicc(gic, GICC_CTLR)), 0x00000000);
+
+    // Global disable forwarding interrupts from distributor to cpu interface
+    REG_WRITE32(REG(gicd(gic, GICD_CTLR)), 0x00000000);
+}
+
+static void gic_cpu_set_priority(struct gic *gic, char priority)
+{
+    REG_WRITE32(REG(gicc(gic, GICC_PMR)), priority & 0x000000FF);
+}
+
+static unsigned long gic_readiar(struct gic *gic) {
+    return REG_READ32(REG(gicc(gic, GICC_IAR))) & 0x000003FF; // Interrupt ID
+}
+
+static void gic_eoir(struct gic *gic, uint32_t irq) {
+    REG_WRITE32(REG(gicc(gic, GICC_EOIR)), irq & 0x000003FF);
+}
+
+//FIXME Get event_irq from dt
+#define EVENTS_IRQ 31
+#define VIRTUALTIMER_IRQ 27
+
+static void gic_handler(void) {
+    unsigned int irq = gic_readiar(&gic);
+
+    DEBUG("IRQ received : %i\n", irq);
+    switch(irq) {
+    case EVENTS_IRQ:
+        do_hypervisor_callback(NULL);
+        break;
+    case VIRTUALTIMER_IRQ:
+        timer_handler(0, NULL, 0);
+        break;
+    default:
+        DEBUG("Unhandled irq\n");
+        break;
+    }
+
+    DEBUG("EIRQ\n");
+
+    gic_eoir(&gic, irq);
+}
+
+void gic_init(void) {
+    gic.gicd_base = NULL;
+    int node = 0;
+    int depth = 0;
+    for (;;)
+    {
+        node = fdt_next_node(device_tree, node, &depth);
+        if (node <= 0 || depth < 0)
+            break;
+
+        if (fdt_getprop(device_tree, node, "interrupt-controller", NULL)) {
+            int len = 0;
+
+            if (fdt_node_check_compatible(device_tree, node, "arm,cortex-a15-gic") &&
+                fdt_node_check_compatible(device_tree, node, "arm,cortex-a7-gic")) {
+                printk("Skipping incompatible interrupt-controller node\n");
+                continue;
+            }
+
+            const uint64_t *reg = fdt_getprop(device_tree, node, "reg", &len);
+
+            /* We have two registers (GICC and GICD), each of which contains
+             * two parts (an address and a size), each of which is a 64-bit
+             * value (8 bytes), so we expect a length of 2 * 2 * 8 = 32.
+             * If any extra values are passed in future, we ignore them. */
+            if (reg == NULL || len < 32) {
+                printk("Bad 'reg' property: %p %d\n", reg, len);
+                continue;
+            }
+
+            gic.gicd_base = to_virt((long) fdt64_to_cpu(reg[0]));
+            gic.gicc_base = to_virt((long) fdt64_to_cpu(reg[2]));
+            printk("Found GIC: gicd_base = %p, gicc_base = %p\n", gic.gicd_base, gic.gicc_base);
+            break;
+        }
+    }
+    if (!gic.gicd_base) {
+        printk("GIC not found!\n");
+        BUG();
+    }
+    wmb();
+
+    /* Note: we could mark this as "device" memory here, but Xen will have already
+     * set it that way in the second stage translation table, so it's not necessary.
+     * See "Overlaying the memory type attribute" in the Architecture Reference Manual.
+     */
+
+    IRQ_handler = gic_handler;
+
+    gic_disable_interrupts(&gic);
+    gic_cpu_set_priority(&gic, 0xff);
+
+    /* Must call gic_enable_interrupts before enabling individual interrupts, otherwise our IRQ handler
+     * gets called endlessly with spurious interrupts. */
+    gic_enable_interrupts(&gic);
+
+    gic_enable_interrupt(&gic, EVENTS_IRQ /* interrupt number */, 0x1 /*cpu_set*/, 1 /*level_sensitive*/, 0 /* ppi */);
+    gic_enable_interrupt(&gic, VIRTUALTIMER_IRQ /* interrupt number */, 0x1 /*cpu_set*/, 1 /*level_sensitive*/, 1 /* ppi */);
+}
-- 
2.0.1