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| author | Gregory Fuchedgi <gfuchedgi@gmail.com> | 2026-04-30 00:54:14 +0300 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-05-02 20:16:27 +0300 |
| commit | 383d0fb8946921b4914ea0f360342e221d419d40 (patch) | |
| tree | 2c9340f5ce15d1e81a4319066ebee245051dd5db | |
| parent | 851bba8068d15f5a386da544096f7ed6bc16e551 (diff) | |
| download | linux-383d0fb8946921b4914ea0f360342e221d419d40.tar.xz | |
amd-xgbe: fix PTP addend overflow causing frozen clock
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: fbd47be098b5 ("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>
| -rw-r--r-- | drivers/net/ethernet/amd/xgbe/xgbe.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/net/ethernet/amd/xgbe/xgbe.h b/drivers/net/ethernet/amd/xgbe/xgbe.h index 60b7e53206d1..3d3b09010d48 100644 --- a/drivers/net/ethernet/amd/xgbe/xgbe.h +++ b/drivers/net/ethernet/amd/xgbe/xgbe.h @@ -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 |