Introduce bus_get_bus_tag() method

Provide bus_get_bus_tag() for sparc64, powerpc, arm, arm64 and mips
nexus and its children in order to return a platform specific default tag.

This is required to ensure generic correctness of the bus_space tag.
It is especially needed for arches where child bus tag does not match
the parent bus tag. This solves the problem with ppc architecture
where the PCI bus tag differs from parent bus tag which is big-endian.

This commit is a part of the following patch:
https://reviews.freebsd.org/D4879

Submitted by:  Marcin Mazurek <mma@semihalf.com>
Obtained from: Semihalf
Sponsored by:  Annapurna Labs
Reviewed by:   jhibbits, mmel
Differential Revision: https://reviews.freebsd.org/D4879

sys/arm/arm/nexus.c

@@ -85,6 +85,7 @@ static	struct resource *nexus_alloc_resource(device_t, device_t, int, int *,
     rman_res_t, rman_res_t, rman_res_t, u_int);
 static	int nexus_activate_resource(device_t, device_t, int, int,
     struct resource *);
+static bus_space_tag_t nexus_get_bus_tag(device_t, device_t);
 #ifdef ARM_INTRNG
 #ifdef SMP
 static	int nexus_bind_intr(device_t, device_t, struct resource *, int);
@@ -124,6 +125,7 @@ static device_method_t nexus_methods[] = {
 	DEVMETHOD(bus_release_resource,	nexus_release_resource),
 	DEVMETHOD(bus_setup_intr,	nexus_setup_intr),
 	DEVMETHOD(bus_teardown_intr,	nexus_teardown_intr),
+	DEVMETHOD(bus_get_bus_tag,	nexus_get_bus_tag),
 #ifdef ARM_INTRNG
 	DEVMETHOD(bus_describe_intr,	nexus_describe_intr),
 #ifdef SMP
@@ -260,6 +262,17 @@ nexus_release_resource(device_t bus, device_t child, int type, int rid,
 	return (rman_release_resource(res));
 }
 
+static bus_space_tag_t
+nexus_get_bus_tag(device_t bus __unused, device_t child __unused)
+{
+
+#ifdef FDT
+		return(fdtbus_bs_tag);
+#else
+		return((void *)1);
+#endif
+}
+
 static int
 nexus_config_intr(device_t dev, int irq, enum intr_trigger trig,
     enum intr_polarity pol)

sys/arm64/arm64/nexus.c

@@ -113,6 +113,7 @@ static	int nexus_deactivate_resource(device_t, device_t, int, int,
 static int nexus_setup_intr(device_t dev, device_t child, struct resource *res,
     int flags, driver_filter_t *filt, driver_intr_t *intr, void *arg, void **cookiep);
 static int nexus_teardown_intr(device_t, device_t, struct resource *, void *);
+static bus_space_tag_t nexus_get_bus_tag(device_t, device_t);
 #ifdef SMP
 static int nexus_bind_intr(device_t, device_t, struct resource *, int);
 #endif
@@ -134,6 +135,7 @@ static device_method_t nexus_methods[] = {
 	DEVMETHOD(bus_deactivate_resource,	nexus_deactivate_resource),
 	DEVMETHOD(bus_setup_intr,	nexus_setup_intr),
 	DEVMETHOD(bus_teardown_intr,	nexus_teardown_intr),
+	DEVMETHOD(bus_get_bus_tag,	nexus_get_bus_tag),
 #ifdef SMP
 	DEVMETHOD(bus_bind_intr,	nexus_bind_intr),
 #endif
@@ -307,6 +309,13 @@ nexus_bind_intr(device_t dev, device_t child, struct resource *irq, int cpu)
 }
 #endif
 
+static bus_space_tag_t
+nexus_get_bus_tag(device_t bus __unused, device_t child __unused)
+{
+
+	return(&memmap_bus);
+}
+
 static int
 nexus_activate_resource(device_t bus, device_t child, int type, int rid,
     struct resource *r)

sys/kern/bus_if.m

@@ -636,6 +636,17 @@ METHOD bus_dma_tag_t get_dma_tag {
 	device_t	_child;
 } DEFAULT bus_generic_get_dma_tag;
 
+/**
+ * @brief Returns bus_space_tag_t for use w/ devices on the bus.
+ *
+ * @param _dev		the parent device of @p _child
+ * @param _child	the device to which the tag will belong
+ */
+METHOD bus_space_tag_t get_bus_tag {
+	device_t	_dev;
+	device_t	_child;
+} DEFAULT bus_generic_get_bus_tag;
+
 /**
  * @brief Allow the bus to determine the unit number of a device.
  *

sys/kern/subr_bus.c

@@ -4094,6 +4094,22 @@ bus_generic_get_dma_tag(device_t dev, device_t child)
 	return (NULL);
 }
 
+/**
+ * @brief Helper function for implementing BUS_GET_BUS_TAG().
+ *
+ * This simple implementation of BUS_GET_BUS_TAG() simply calls the
+ * BUS_GET_BUS_TAG() method of the parent of @p dev.
+ */
+bus_space_tag_t
+bus_generic_get_bus_tag(device_t dev, device_t child)
+{
+
+	/* Propagate up the bus hierarchy until someone handles it. */
+	if (dev->parent != NULL)
+		return (BUS_GET_BUS_TAG(dev->parent, child));
+	return (NULL);
+}
+
 /**
  * @brief Helper function for implementing BUS_GET_RESOURCE().
  *
@@ -4575,6 +4591,23 @@ bus_get_dma_tag(device_t dev)
 	return (BUS_GET_DMA_TAG(parent, dev));
 }
 
+/**
+ * @brief Wrapper function for BUS_GET_BUS_TAG().
+ *
+ * This function simply calls the BUS_GET_BUS_TAG() method of the
+ * parent of @p dev.
+ */
+bus_space_tag_t
+bus_get_bus_tag(device_t dev)
+{
+	device_t parent;
+
+	parent = device_get_parent(dev);
+	if (parent == NULL)
+		return (NULL);
+	return (BUS_GET_BUS_TAG(parent, dev));
+}
+
 /**
  * @brief Wrapper function for BUS_GET_DOMAIN().
  *

sys/powerpc/powerpc/nexus.c

@@ -66,6 +66,7 @@ static bus_setup_intr_t nexus_setup_intr;
 static bus_teardown_intr_t nexus_teardown_intr;
 static bus_activate_resource_t nexus_activate_resource;
 static bus_deactivate_resource_t nexus_deactivate_resource;
+static bus_space_tag_t nexus_get_bus_tag(device_t, device_t);
 #ifdef SMP
 static bus_bind_intr_t nexus_bind_intr;
 #endif
@@ -87,6 +88,7 @@ static device_method_t nexus_methods[] = {
 	DEVMETHOD(bus_bind_intr,	nexus_bind_intr),
 #endif
 	DEVMETHOD(bus_config_intr,	nexus_config_intr),
+	DEVMETHOD(bus_get_bus_tag,	nexus_get_bus_tag),
 
 	/* ofw_bus interface */
 	DEVMETHOD(ofw_bus_map_intr,	nexus_ofw_map_intr),
@@ -155,6 +157,13 @@ nexus_teardown_intr(device_t bus __unused, device_t child __unused,
 	return (powerpc_teardown_intr(ih));
 }
 
+static bus_space_tag_t
+nexus_get_bus_tag(device_t bus __unused, device_t child __unused)
+{
+
+	return(&bs_be_tag);
+}
+
 #ifdef SMP
 static int
 nexus_bind_intr(device_t bus __unused, device_t child __unused,

sys/sparc64/sparc64/nexus.c

@@ -98,6 +98,7 @@ static bus_bind_intr_t nexus_bind_intr;
 #endif
 static bus_describe_intr_t nexus_describe_intr;
 static bus_get_dma_tag_t nexus_get_dma_tag;
+static bus_get_bus_tag_t nexus_get_bus_tag;
 static ofw_bus_get_devinfo_t nexus_get_devinfo;
 
 static int nexus_inlist(const char *, const char *const *);
@@ -135,6 +136,7 @@ static device_method_t nexus_methods[] = {
 #endif
 	DEVMETHOD(bus_describe_intr,	nexus_describe_intr),
 	DEVMETHOD(bus_get_dma_tag,	nexus_get_dma_tag),
+	DEVMETHOD(bus_get_bus_tag,	nexus_get_bus_tag),
 
 	/* ofw_bus interface */
 	DEVMETHOD(ofw_bus_get_devinfo,	nexus_get_devinfo),
@@ -502,6 +504,13 @@ nexus_get_dma_tag(device_t bus __unused, device_t child __unused)
 	return (&nexus_dmatag);
 }
 
+static bus_space_tag_t
+nexus_get_bus_tag(device_t bus __unused, device_t child __unused)
+{
+
+	return (&nexus_bustag);
+}
+
 static const struct ofw_bus_devinfo *
 nexus_get_devinfo(device_t bus __unused, device_t child)
 {

sys/sys/bus.h

@@ -30,6 +30,7 @@
 #define _SYS_BUS_H_
 
 #include <machine/_limits.h>
+#include <machine/_bus.h>
 #include <sys/_bus_dma.h>
 #include <sys/ioccom.h>
 
@@ -383,6 +384,8 @@ int	bus_generic_detach(device_t dev);
 void	bus_generic_driver_added(device_t dev, driver_t *driver);
 bus_dma_tag_t
 	bus_generic_get_dma_tag(device_t dev, device_t child);
+bus_space_tag_t
+	bus_generic_get_bus_tag(device_t dev, device_t child);
 int	bus_generic_get_domain(device_t dev, device_t child, int *domain);
 struct resource_list *
 	bus_generic_get_resource_list (device_t, device_t);
@@ -448,6 +451,7 @@ int	bus_activate_resource(device_t dev, int type, int rid,
 int	bus_deactivate_resource(device_t dev, int type, int rid,
 				struct resource *r);
 bus_dma_tag_t bus_get_dma_tag(device_t dev);
+bus_space_tag_t bus_get_bus_tag(device_t dev);
 int	bus_get_domain(device_t dev, int *domain);
 int	bus_release_resource(device_t dev, int type, int rid,
 			     struct resource *r);