[SPARC64]: Add hypervisor API negotiation and fix console bugs.

Hypervisor interfaces need to be negotiated in order to use
some API calls reliably.  So add a small set of interfaces
to request API versions and query current settings.

This allows us to fix some bugs in the hypervisor console:

1) If we can negotiate API group CORE of at least major 1
   minor 1 we can use con_read and con_write which can improve
   console performance quite a bit.

2) When we do a console write request, we should hold the
   spinlock around the whole request, not a byte at a time.
   What would happen is that it's easy for output from
   different cpus to get mixed with each other.

3) Use consistent udelay() based polling, udelay(1) each
   loop with a limit of 1000 polls to handle stuck hypervisor
   console.

Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc64/kernel/hvapi.c

@@ -0,0 +1,189 @@
+/* hvapi.c: Hypervisor API management.
+ *
+ * Copyright (C) 2007 David S. Miller <davem@davemloft.net>
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+
+#include <asm/hypervisor.h>
+#include <asm/oplib.h>
+
+/* If the hypervisor indicates that the API setting
+ * calls are unsupported, by returning HV_EBADTRAP or
+ * HV_ENOTSUPPORTED, we assume that API groups with the
+ * PRE_API flag set are major 1 minor 0.
+ */
+struct api_info {
+	unsigned long group;
+	unsigned long major;
+	unsigned long minor;
+	unsigned int refcnt;
+	unsigned int flags;
+#define FLAG_PRE_API		0x00000001
+};
+
+static struct api_info api_table[] = {
+	{ .group = HV_GRP_SUN4V,	.flags = FLAG_PRE_API	},
+	{ .group = HV_GRP_CORE,		.flags = FLAG_PRE_API	},
+	{ .group = HV_GRP_INTR,					},
+	{ .group = HV_GRP_SOFT_STATE,				},
+	{ .group = HV_GRP_PCI,		.flags = FLAG_PRE_API	},
+	{ .group = HV_GRP_LDOM,					},
+	{ .group = HV_GRP_SVC_CHAN,	.flags = FLAG_PRE_API	},
+	{ .group = HV_GRP_NCS,		.flags = FLAG_PRE_API	},
+	{ .group = HV_GRP_NIAG_PERF,	.flags = FLAG_PRE_API	},
+	{ .group = HV_GRP_FIRE_PERF,				},
+	{ .group = HV_GRP_DIAG,		.flags = FLAG_PRE_API	},
+};
+
+static DEFINE_SPINLOCK(hvapi_lock);
+
+static struct api_info *__get_info(unsigned long group)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(api_table); i++) {
+		if (api_table[i].group == group)
+			return &api_table[i];
+	}
+	return NULL;
+}
+
+static void __get_ref(struct api_info *p)
+{
+	p->refcnt++;
+}
+
+static void __put_ref(struct api_info *p)
+{
+	if (--p->refcnt == 0) {
+		unsigned long ignore;
+
+		sun4v_set_version(p->group, 0, 0, &ignore);
+		p->major = p->minor = 0;
+	}
+}
+
+/* Register a hypervisor API specification.  It indicates the
+ * API group and desired major+minor.
+ *
+ * If an existing API registration exists '0' (success) will
+ * be returned if it is compatible with the one being registered.
+ * Otherwise a negative error code will be returned.
+ *
+ * Otherwise an attempt will be made to negotiate the requested
+ * API group/major/minor with the hypervisor, and errors returned
+ * if that does not succeed.
+ */
+int sun4v_hvapi_register(unsigned long group, unsigned long major,
+			 unsigned long *minor)
+{
+	struct api_info *p;
+	unsigned long flags;
+	int ret;
+
+	spin_lock_irqsave(&hvapi_lock, flags);
+	p = __get_info(group);
+	ret = -EINVAL;
+	if (p) {
+		if (p->refcnt) {
+			ret = -EINVAL;
+			if (p->major == major) {
+				*minor = p->minor;
+				ret = 0;
+			}
+		} else {
+			unsigned long actual_minor;
+			unsigned long hv_ret;
+
+			hv_ret = sun4v_set_version(group, major, *minor,
+						   &actual_minor);
+			ret = -EINVAL;
+			if (hv_ret == HV_EOK) {
+				*minor = actual_minor;
+				p->major = major;
+				p->minor = actual_minor;
+				ret = 0;
+			} else if (hv_ret == HV_EBADTRAP ||
+				   HV_ENOTSUPPORTED) {
+				if (p->flags & FLAG_PRE_API) {
+					if (major == 1) {
+						p->major = 1;
+						p->minor = 0;
+						*minor = 0;
+						ret = 0;
+					}
+				}
+			}
+		}
+
+		if (ret == 0)
+			__get_ref(p);
+	}
+	spin_unlock_irqrestore(&hvapi_lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL(sun4v_hvapi_register);
+
+void sun4v_hvapi_unregister(unsigned long group)
+{
+	struct api_info *p;
+	unsigned long flags;
+
+	spin_lock_irqsave(&hvapi_lock, flags);
+	p = __get_info(group);
+	if (p)
+		__put_ref(p);
+	spin_unlock_irqrestore(&hvapi_lock, flags);
+}
+EXPORT_SYMBOL(sun4v_hvapi_unregister);
+
+int sun4v_hvapi_get(unsigned long group,
+		    unsigned long *major,
+		    unsigned long *minor)
+{
+	struct api_info *p;
+	unsigned long flags;
+	int ret;
+
+	spin_lock_irqsave(&hvapi_lock, flags);
+	ret = -EINVAL;
+	p = __get_info(group);
+	if (p && p->refcnt) {
+		*major = p->major;
+		*minor = p->minor;
+		ret = 0;
+	}
+	spin_unlock_irqrestore(&hvapi_lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL(sun4v_hvapi_get);
+
+void __init sun4v_hvapi_init(void)
+{
+	unsigned long group, major, minor;
+
+	group = HV_GRP_SUN4V;
+	major = 1;
+	minor = 0;
+	if (sun4v_hvapi_register(group, major, &minor))
+		goto bad;
+
+	group = HV_GRP_CORE;
+	major = 1;
+	minor = 1;
+	if (sun4v_hvapi_register(group, major, &minor))
+		goto bad;
+
+	return;
+
+bad:
+	prom_printf("HVAPI: Cannot register API group "
+		    "%lx with major(%u) minor(%u)\n",
+		    group, major, minor);
+	prom_halt();
+}