[Intel-wired-lan] [PATCH iwl-net v1 2/5] igc: Lengthen the hardware retry time to prevent timeouts

[christopher.s.hall at intel.com]

From: Christopher S M Hall <christopher.s.hall at intel.com>

Lengthen the hardware retry timer to four microseconds.

The i225/i226 hardware retries if it receives an inappropriate response
from the upstream device. If the device retries too quickly, the root
port does not respond.

The issue can be reproduced with the following:

$ sudo phc2sys -R 1000 -O 0 -i tsn0 -m

Note: 1000 Hz (-R 1000) is unrealistically large, but provides a way to
quickly reproduce the issue.

PHC2SYS exits with:

"ioctl PTP_OFFSET_PRECISE: Connection timed out" when the PTM transaction
  fails

Fixes: 6b8aa753a9f9 ("igc: Decrease PTM short interval from 10 us to 1 us")
Signed-off-by: Christopher S M Hall <christopher.s.hall at intel.com>
---
 drivers/net/ethernet/intel/igc/igc_defines.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/igc/igc_defines.h b/drivers/net/ethernet/intel/igc/igc_defines.h
index ec191d26c650..253327c23903 100644
--- a/drivers/net/ethernet/intel/igc/igc_defines.h
+++ b/drivers/net/ethernet/intel/igc/igc_defines.h
@@ -564,7 +564,7 @@
 #define IGC_PTM_CTRL_SHRT_CYC(usec)	(((usec) & 0x3f) << 2)
 #define IGC_PTM_CTRL_PTM_TO(usec)	(((usec) & 0xff) << 8)
 
-#define IGC_PTM_SHORT_CYC_DEFAULT	1   /* Default short cycle interval */
+#define IGC_PTM_SHORT_CYC_DEFAULT	4   /* Default short cycle interval */
 #define IGC_PTM_CYC_TIME_DEFAULT	5   /* Default PTM cycle time */
 #define IGC_PTM_TIMEOUT_DEFAULT		255 /* Default timeout for PTM errors */
 
-- 
2.34.1