Subject: [PATCH net-next v3 0/3] net: stmmac: dwmac: enforce preamble before SFD for i.MX8MP

From: Stefan Eichenberger <[email-masked]>
Date: Tue, 20 Jan 2026 21:30:01 +0100

This series adds a new phy_device flag PHY_F_KEEP_PREAMBLE_BEFORE_SFD
that allows a MAC driver to request to keep the preamble bytes before
the start frame delimiter (SFD) when receiving frames from the PHY.

This flag is set in the stmmac driver for the i.MX8MP SoC due to errata
(ERR050694), which causes it to drop frames without a preamble.

The Micrel KSZ9131 PHY supports keeping the preamble before SFD by
setting an undocumented flag, that was confirmed by NXP and Micrel. This
new feature has been added to the Micrel PHY driver for the KSZ9131 PHY.

Changes since v2:
- Instead of using phy_register_fixup add a new phy_device::dev_flags
  flag PHY_F_KEEP_PREAMBLE_BEFORE_SFD so that a MAC can request to keep
  the preamble before SFD if needed (Russell)
- Link to v2: https://lore.kernel.org/all/[email-masked]/

Changes since v1:
- Use phy_register_fixup_for_uid() instead of adding a new device tree
  property
- I will send the conversion of the micrel.txt binding as a separate
  patch series
- Link to v1: https://lore.kernel.org/all/[email-masked]/

Stefan Eichenberger (3):
  net: phy: add a new phy_device flag to keep preamble before sfd
  net: phy: micrel: add option to keep the preamble before sfd for
    KSZ9131
  net: stmmac: dwmac-imx: keep preamble before sfd on i.MX8MP

 drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c   |  6 +++++-
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c |  8 +++++++-
 drivers/net/phy/micrel.c                          | 14 +++++++++++++-
 include/linux/phy.h                               |  5 +++--
 include/linux/stmmac.h                            |  1 +
 5 files changed, 29 insertions(+), 5 deletions(-)

-- 
2.51.0