[PATCH 4.19 25/77] net: ethernet: ti: cpts: fix ethtool output when no ptp_clock registered

From: Grygorii Strashko <grygorii.strashko@ti.com>

[ Upstream commit 4614792eebcbf81c60ad3604c1aeeb2b0899cea4 ]

The CPTS driver registers PTP PHC clock when first netif is going up and
unregister it when all netif are down. Now ethtool will show:
 - PTP PHC clock index 0 after boot until first netif is up;
 - the last assigned PTP PHC clock index even if PTP PHC clock is not
registered any more after all netifs are down.

This patch ensures that -1 is returned by ethtool when PTP PHC clock is not
registered any more.

Fixes: 8a2c9a5ab4b9 ("net: ethernet: ti: cpts: rework initialization/deinitialization")
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Link: https://lore.kernel.org/r/20201224162405.28032-1-grygorii.strashko@ti.com (local)
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/ethernet/ti/cpts.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/net/ethernet/ti/cpts.c
+++ b/drivers/net/ethernet/ti/cpts.c

@@ -476,6 +476,7 @@ void cpts_unregister(struct cpts *cpts)
 
 	ptp_clock_unregister(cpts->clock);
 	cpts->clock = NULL;
+	cpts->phc_index = -1;
 
 	cpts_write32(cpts, 0, int_enable);
 	cpts_write32(cpts, 0, control);

@@ -577,6 +578,7 @@ struct cpts *cpts_create(struct device *
 	cpts->cc.read = cpts_systim_read;
 	cpts->cc.mask = CLOCKSOURCE_MASK(32);
 	cpts->info = cpts_info;
+	cpts->phc_index = -1;
 
 	cpts_calc_mult_shift(cpts);
 	/* save cc.mult original value as it can be modified