mirrors/linux
2
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2026-05-16 03:11:11 -04:00
Code Issues Packages Projects Releases Wiki Activity

amd-xgbe: fix PTP addend overflow causing frozen clock

Browse Source 
XGBE_PTP_ACT_CLK_FREQ and XGBE_V2_PTP_ACT_CLK_FREQ were 10x too
large (500MHz/1GHz instead of 50MHz/100MHz), causing the computed
addend to overflow the 32-bit tstamp_addend. In the general case
this would result in the clock advancing at the wrong rate. For v2
(PCI), ptpclk_rate is hardcoded to 125MHz, so the addend formula
(ACT_CLK_FREQ << 32) / ptpclk_rate yields exactly 8 * 2^32, and
when stored to the 32-bit tstamp_addend the value is zero. With
addend = 0 the hardware accumulator never overflows and the PTP
clock is fully stopped. For v1 (platform), ptpclk_rate is read from
ACPI/DT so the exact overflow behavior depends on the
firmware-reported frequency.

Define the constants as NSEC_PER_SEC / SSINC so the relationship is
explicit and cannot drift out of sync.

Fixes: fbd47be098 ("amd-xgbe: add hardware PTP timestamping support")
Tested-by: Gregory Fuchedgi <gfuchedgi@gmail.com>
Signed-off-by: Gregory Fuchedgi <gfuchedgi@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260429-fix-xgbe-ptp-addend-v1-1-fca5b0ca5e62@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Gregory Fuchedgi
2026-04-29 14:54:14 -07:00
committed by Jakub Kicinski
parent 851bba8068
commit 383d0fb894
1 changed files with 2 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/net/ethernet/amd/xgbe/xgbe.h
View File

@@ -135,11 +135,11 @@
*/
#define XGBE_TSTAMP_SSINC 20
#define XGBE_TSTAMP_SNSINC 0
#define XGBE_PTP_ACT_CLK_FREQ 500000000
#define XGBE_PTP_ACT_CLK_FREQ (NSEC_PER_SEC / XGBE_TSTAMP_SSINC)
#define XGBE_V2_TSTAMP_SSINC 0xA
#define XGBE_V2_TSTAMP_SNSINC 0
#define XGBE_V2_PTP_ACT_CLK_FREQ 1000000000
#define XGBE_V2_PTP_ACT_CLK_FREQ (NSEC_PER_SEC / XGBE_V2_TSTAMP_SSINC)
/* Define maximum supported values */
#define XGBE_MAX_PPS_OUT 4