UBUNTU: SAUCE: hv: make clocksource available for PTP device supporting

BugLink: http://bugs.launchpad.net/bugs/1676635

Make the MSR and TSC clock sources available during the hv_init() and
export them via hyperv_cs in a similar way as the following upstream
commit does:

commit dee863b5 ("hv: export current Hyper-V clocksource")
Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Acked-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

arch/x86/kernel/cpu/mshyperv.c

@@ -134,26 +134,6 @@ static uint32_t  __init ms_hyperv_platform(void)
 	return 0;
 }
 
-static cycle_t read_hv_clock(struct clocksource *arg)
-{
-	cycle_t current_tick;
-	/*
-	 * Read the partition counter to get the current tick count. This count
-	 * is set to 0 when the partition is created and is incremented in
-	 * 100 nanosecond units.
-	 */
-	rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
-	return current_tick;
-}
-
-static struct clocksource hyperv_cs = {
-	.name		= "hyperv_clocksource",
-	.rating		= 400, /* use this when running on Hyperv*/
-	.read		= read_hv_clock,
-	.mask		= CLOCKSOURCE_MASK(64),
-	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
-};
-
 static unsigned char hv_get_nmi_reason(void)
 {
 	return 0;
@@ -209,9 +189,6 @@ static void __init ms_hyperv_init_platform(void)
 			     "hv_nmi_unknown");
 #endif
 
-	if (ms_hyperv.features & HV_X64_MSR_TIME_REF_COUNT_AVAILABLE)
-		clocksource_register_hz(&hyperv_cs, NSEC_PER_SEC/100);
-
 #ifdef CONFIG_X86_IO_APIC
 	no_timer_check = 1;
 #endif

drivers/hv/hv.c

@@ -191,6 +191,28 @@ static struct clocksource hyperv_cs_tsc = {
 };
 #endif
 
+static cycle_t read_hv_clock_msr(struct clocksource *arg)
+{
+	cycle_t current_tick;
+	/*
+	 * Read the partition counter to get the current tick count. This count
+	 * is set to 0 when the partition is created and is incremented in
+	 * 100 nanosecond units.
+	 */
+	rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
+	return current_tick;
+}
+
+static struct clocksource hyperv_cs_msr = {
+	.name		= "hyperv_clocksource_msr",
+	.rating		= 400, /* use this when running on Hyperv*/
+	.read		= read_hv_clock_msr,
+	.mask		= CLOCKSOURCE_MASK(64),
+	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+struct clocksource *hyperv_cs;
+EXPORT_SYMBOL_GPL(hyperv_cs);
 
 /*
  * hv_init - Main initialization routine.
@@ -254,9 +276,11 @@ int hv_init(void)
 
 		va_tsc = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL);
 		if (!va_tsc)
-			goto cleanup;
+			goto register_msr_cs;
 		hv_context.tsc_page = va_tsc;
 
+		hyperv_cs = &hyperv_cs_tsc;
+
 		rdmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
 
 		tsc_msr.enable = 1;
@@ -265,7 +289,17 @@ int hv_init(void)
 		wrmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
 		clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
 	}
+register_msr_cs:
 #endif
+	/*
+	 * For 32 bit guests just use the MSR based mechanism for reading
+	 * the partition counter.
+	 */
+
+	hyperv_cs = &hyperv_cs_msr;
+	if (ms_hyperv.features & HV_X64_MSR_TIME_REF_COUNT_AVAILABLE)
+		clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
+
 	return 0;
 
 cleanup:

drivers/hv/hyperv_vmbus.h

@@ -29,6 +29,7 @@
 #include <asm/sync_bitops.h>
 #include <linux/atomic.h>
 #include <linux/hyperv.h>
+#include <linux/clocksource.h>
 
 /*
  * Timeout for services such as KVP and fcopy.
@@ -719,4 +720,6 @@ enum hvutil_device_state {
 	HVUTIL_DEVICE_DYING,     /* driver unload is in progress */
 };
 
+extern struct clocksource *hyperv_cs;
+
 #endif /* _HYPERV_VMBUS_H */