Make a pass through all drivers checking specs for desired behavior on

SMP systems.  It appears all drivers except ichss should attach to each
CPU and that settings should be performed on each CPU.  Add comments about
this.  Also, add a guard for p4tcc's identify method being called more than
once.

4 files changed, 25 insertions, 1 deletions

diff --git a/sys/dev/acpica/acpi_perf.c b/sys/dev/acpica/acpi_perf.c
index 2307000..ab17a56 100644
--- a/sys/dev/acpica/acpi_perf.c
+++ b/sys/dev/acpica/acpi_perf.c
@@ -152,6 +152,11 @@ acpi_perf_identify(driver_t *driver, device_t parent)
 		return;
 	if (ACPI_FAILURE(AcpiEvaluateObject(handle, "_PSS", NULL, NULL)))
 		return;
+
+	/*
+	 * Add a child to every CPU that has the right methods.  In future
+	 * versions of the ACPI spec, CPUs can have different settings.
+	 */
 	if (BUS_ADD_CHILD(parent, 0, "acpi_perf", -1) == NULL)
 		device_printf(parent, "add acpi_perf child failed\n");
 }
diff --git a/sys/dev/cpufreq/ichss.c b/sys/dev/cpufreq/ichss.c
index b8d3542..d38ed52 100644
--- a/sys/dev/cpufreq/ichss.c
+++ b/sys/dev/cpufreq/ichss.c
@@ -166,7 +166,11 @@ ichss_pci_probe(device_t dev)
 	if (devclass_get_device(ichss_devclass, 0))
 		return (ENXIO);
 
-	/* Add a child under the CPU parent. */
+	/*
+	 * Add a child under the CPU parent.  It appears that ICH SpeedStep
+	 * only requires a single CPU to set the value (since the chipset
+	 * is shared by all CPUs.)  Thus, we only add a child to cpu 0.
+	 */
 	parent = devclass_get_device(devclass_find("cpu"), 0);
 	KASSERT(parent != NULL, ("cpu parent is NULL"));
 	child = BUS_ADD_CHILD(parent, 0, "ichss", 0);
diff --git a/sys/i386/cpufreq/est.c b/sys/i386/cpufreq/est.c
index 53b1cd7..6239332 100644
--- a/sys/i386/cpufreq/est.c
+++ b/sys/i386/cpufreq/est.c
@@ -582,6 +582,10 @@ est_identify(driver_t *driver, device_t parent)
 	if ((p[2] & 0x80) == 0)
 		return;
 
+	/*
+	 * We add a child for each CPU since settings must be performed
+	 * on each CPU in the SMP case.
+	 */
 	if (BUS_ADD_CHILD(parent, 0, "est", -1) == NULL)
 		device_printf(parent, "add est child failed\n");
 }
diff --git a/sys/i386/cpufreq/p4tcc.c b/sys/i386/cpufreq/p4tcc.c
index cff04fe..b8cf66e 100644
--- a/sys/i386/cpufreq/p4tcc.c
+++ b/sys/i386/cpufreq/p4tcc.c
@@ -102,6 +102,17 @@ p4tcc_identify(driver_t *driver, device_t parent)
 
 	if ((cpu_feature & (CPUID_ACPI | CPUID_TM)) != (CPUID_ACPI | CPUID_TM))
 		return;
+
+	/* Make sure we're not being doubly invoked. */
+	if (device_find_child(parent, "p4tcc", -1) != NULL)
+		return;
+
+	/*
+	 * We attach a p4tcc child for every CPU since settings need to
+	 * be performed on every CPU in the SMP case.  See section 13.15.3
+	 * of the IA32 Intel Architecture Software Developer's Manual,
+	 * Volume 3, for more info.
+	 */
 	if (BUS_ADD_CHILD(parent, 0, "p4tcc", -1) == NULL)
 		device_printf(parent, "add p4tcc child failed\n");
 }