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dpll: expose fractional frequency offset in ppt

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Currently, the dpll subsystem exports the fractional frequency offset
(FFO) in parts per million (ppm). This granularity is insufficient for
high-precision synchronization scenarios which often require parts per
trillion (ppt) resolution.

Add a new netlink attribute DPLL_A_PIN_FRACTIONAL_FREQUENCY_OFFSET_PPT
to expose the FFO in ppt.

Update the dpll netlink core to expect the driver-provided FFO value
to be in ppt. To maintain backward compatibility with existing userspace
tools, populate the legacy DPLL_A_PIN_FRACTIONAL_FREQUENCY_OFFSET
attribute by dividing the new ppt value by 1,000,000.

Update the zl3073x and mlx5 drivers to provide the FFO value in ppt:
- zl3073x: adjust the fixed-point calculation to produce ppt (10^12)
  instead of ppm (10^6).
- mlx5: scale the existing ppm value by 1,000,000.

Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Reviewed-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://patch.msgid.link/20260126162253.27890-1-ivecera@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Ivan Vecera
2026-01-26 17:22:51 +01:00
committed by Jakub Kicinski
parent b3827c91cc
commit bc443c253f
5 changed files with 27 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
drivers/dpll/dpll_netlink.c
View File

@@ -389,7 +389,15 @@ static int dpll_msg_add_ffo(struct sk_buff *msg, struct dpll_pin *pin,
return 0;
return ret;
}
return nla_put_sint(msg, DPLL_A_PIN_FRACTIONAL_FREQUENCY_OFFSET, ffo);
/* Put the FFO value in PPM to preserve compatibility with older
* programs.
*/
ret = nla_put_sint(msg, DPLL_A_PIN_FRACTIONAL_FREQUENCY_OFFSET,
div_s64(ffo, 1000000));
if (ret)
return -EMSGSIZE;
return nla_put_sint(msg, DPLL_A_PIN_FRACTIONAL_FREQUENCY_OFFSET_PPT,
ffo);
}
static int

7
drivers/dpll/zl3073x/core.c
View File

@@ -710,8 +710,11 @@ zl3073x_ref_ffo_update(struct zl3073x_dev *zldev)
if (rc)
return rc;
/* Convert to ppm -> ffo = (10^6 * value) / 2^32 */
zldev->ref[i].ffo = mul_s64_u64_shr(value, 1000000, 32);
/* Convert to ppt
* ffo = (10^12 * value) / 2^32
* ffo = ( 5^12 * value) / 2^20
*/
zldev->ref[i].ffo = mul_s64_u64_shr(value, 244140625, 20);
}
return 0;