[PATCH net 2/5] e1000e: do not cache the hwtstamp config before it is applied

[Linkui Xiao <xiaolinkui@126.com>]

From: Linkui Xiao <xiaolinkui@kylinos.cn>

e1000e_config_hwtstamp() stores the requested configuration in
adapter->hwtstamp_config right after the rx filter has been
translated, but the two register writes that follow are verified by
reading the registers back and each of them can fail with -EAGAIN.

When one of them does, the driver is left holding a configuration the
hardware never accepted:

 - e1000e_hwtstamp_get() hands it back to user space, so an
   application that reads the configuration back is told that
   hardware time stamping is in effect while it is not;

 - e1000e_systim_reset() re-applies it after every reset, including
   the ones the watchdog triggers, and keeps failing;

 - e1000_watchdog() starts polling TSYNCRXCTL_VALID for the cached rx
   filter, and e1000_xmit_frame() still parks skbs that ask for a Tx
   time stamp because it only looks at FLAG_HAS_HW_TIMESTAMP, so they
   are eventually dropped by e1000e_tx_hwtstamp_work() with a
   "clearing Tx timestamp hang" warning.

Cache the configuration only once both registers have been verified,
so that adapter->hwtstamp_config always describes what the hardware
is programmed with.

Fixes: 62d7e3a2d006 ("e1000e: Validate hwtstamp_config completely before applying it")
Cc: stable@vger.kernel.org
Signed-off-by: Linkui Xiao <xiaolinkui@kylinos.cn>
---
 drivers/net/ethernet/intel/e1000e/netdev.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
index 35f5590228eb..7ae33273734f 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -3715,8 +3715,6 @@ static int e1000e_config_hwtstamp(struct e1000_adapter *adapter,
 		return -ERANGE;
 	}
 
-	adapter->hwtstamp_config = *config;
-
 	/* enable/disable Tx h/w time stamping */
 	regval = er32(TSYNCTXCTL);
 	regval &= ~E1000_TSYNCTXCTL_ENABLED;
@@ -3763,6 +3761,8 @@ static int e1000e_config_hwtstamp(struct e1000_adapter *adapter,
 	er32(RXSTMPH);
 	er32(TXSTMPH);
 
+	adapter->hwtstamp_config = *config;
+
 	return 0;
 }
 
-- 
2.25.1