igb: offer a PTP Hardware Clock instead of the timecompare method

This commit removes the legacy timecompare code from the igb driver and
offers a tunable PHC instead.

Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/ethernet/intel/Kconfig b/drivers/net/ethernet/intel/Kconfig
index 7621316..90142aa 100644
--- a/drivers/net/ethernet/intel/Kconfig
+++ b/drivers/net/ethernet/intel/Kconfig
@@ -120,6 +120,17 @@
 	  driver.  DCA is a method for warming the CPU cache before data
 	  is used, with the intent of lessening the impact of cache misses.
 
+config IGB_PTP
+	bool "PTP Hardware Clock (PHC)"
+	default y
+	depends on IGB && PTP_1588_CLOCK
+	---help---
+	  Say Y here if you want to use PTP Hardware Clock (PHC) in the
+	  driver.  Only the basic clock operations have been implemented.
+
+	  Every timestamp and clock read operations must consult the
+	  overflow counter to form a correct time value.
+
 config IGBVF
 	tristate "Intel(R) 82576 Virtual Function Ethernet support"
 	depends on PCI