[PATCH net] net: stmmac: ptp: fix support for PTP_EXTTS_REQUEST2 ioctl

[James Clark <jjc@jclark.com>]

Commit 7c571ac57d9d ("net: ptp: introduce .supported_extts_flags to
ptp_clock_info") modified the PTP core to validate the supported flags
of external timestamp requests, rather than relying on each driver to
check them.

stmmac_enable() and dwmac1000_ptp_enable() ignore the flags, and
neither stmmac_ptp_clock_ops nor dwmac1000_ptp_clock_ops was given any
.supported_extts_flags. Since PTP_EXTTS_REQUEST2 always implies
PTP_STRICT_FLAGS, the core now rejects every PTP_EXTTS_REQUEST2 for
this driver with -EOPNOTSUPP, where before that commit the same
requests succeeded. Only the PTP_EXTTS_REQUEST ioctl still works.

Tests on an NXP i.MX 8M Plus (FRDM-IMX8MPLUS, GMAC 5.10a) show that the
auxiliary snapshot inputs timestamp just the rising edge. The reference
manuals for the STM32MP13 (GMAC 4.20a) and the Cyclone V HPS (GMAC
3.70a, which uses dwmac1000_ptp_clock_ops) say the same.

Encode this in .supported_extts_flags. A PTP_EXTTS_REQUEST2 for the
rising edge then succeeds, and one for the falling edge or for both
edges fails with -EOPNOTSUPP.

Fixes: 7c571ac57d9d ("net: ptp: introduce .supported_extts_flags to ptp_clock_info")
Cc: stable@vger.kernel.org
Signed-off-by: James Clark <jjc@jclark.com>
---
I used an LLM coding assistant to help prepare this patch.

 drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
index a37405534beb..31a66e855d6b 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
@@ -277,6 +277,7 @@ const struct ptp_clock_info stmmac_ptp_clock_ops = {
 	.n_per_out = 0, /* will be overwritten in stmmac_ptp_register */
 	.n_pins = 0,
 	.pps = 0,
+	.supported_extts_flags = PTP_RISING_EDGE | PTP_STRICT_FLAGS,
 	.adjfine = stmmac_adjust_freq,
 	.adjtime = stmmac_adjust_time,
 	.gettimex64 = stmmac_get_timex,
@@ -294,6 +295,7 @@ const struct ptp_clock_info dwmac1000_ptp_clock_ops = {
 	.n_per_out = 0,
 	.n_pins = 0,
 	.pps = 0,
+	.supported_extts_flags = PTP_RISING_EDGE | PTP_STRICT_FLAGS,
 	.adjfine = stmmac_adjust_freq,
 	.adjtime = stmmac_adjust_time,
 	.gettimex64 = stmmac_get_timex,
-- 
2.56.0