netdev - [PATCH net-next 2/2] net/mlx5: Implement ptp_clock

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Date:   Fri,  2 Dec 2022 12:15:31 -0800
From:   Rahul Rameshbabu <rrameshbabu@...dia.com>
To:     Saeed Mahameed <saeedm@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Richard Cochran <richardcochran@...il.com>,
        Rahul Rameshbabu <rrameshbabu@...dia.com>,
        Jacob Keller <jacob.e.keller@...el.com>,
        Aya Levin <ayal@...dia.com>, Gal Pressman <gal@...dia.com>
Cc:     netdev@...r.kernel.org
Subject: [PATCH net-next 2/2] net/mlx5: Implement ptp_clock_info .getfine function

.getfine gives the driver the ability to report the frequency offset from
the device. The frequency offset from the nominal frequency is reported by
the driver in scaled 16-bit fractional parts-per-million.

Signed-off-by: Rahul Rameshbabu <rrameshbabu@...dia.com>
Reviewed-by: Gal Pressman <gal@...dia.com>
Acked-by: Saeed Mahameed <saeedm@...dia.com>
---
 .../ethernet/mellanox/mlx5/core/lib/clock.c   | 35 +++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c b/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
index 69cfe60c558a..4ecf67f617c0 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
@@ -326,6 +326,40 @@ static int mlx5_ptp_adjtime(struct ptp_clock_info *ptp, s64 delta)
 	return 0;
 }
 
+static int mlx5_ptp_getfine(struct ptp_clock_info *ptp, long *scaled_ppm)
+{
+	struct mlx5_clock *clock = container_of(ptp, struct mlx5_clock, ptp_info);
+	u32 in[MLX5_ST_SZ_DW(mtutc_reg)] = {};
+	u32 out[MLX5_ST_SZ_DW(mtutc_reg)];
+	struct mlx5_core_dev *mdev;
+	s64 delta;
+	int err;
+
+	mdev = container_of(clock, struct mlx5_core_dev, clock);
+
+	err = mlx5_core_access_reg(mdev, in, sizeof(in), out, sizeof(out),
+				   MLX5_REG_MTUTC, 0, 0);
+	if (err)
+		return err;
+
+	delta = MLX5_GET(mtutc_reg, out, freq_adjustment);
+	/* Convert parts-per-billion (10^-9) to parts-per-million (10^-6)
+	 * with a 16 bit binary fractional field
+	 *
+	 *    scaled_ppm = ppb * 2^16 / 1000
+	 *
+	 * which is equivalent to
+	 *
+	 *    scaled_ppm = ppb * 2^13 / 125
+	 */
+	delta <<= 13;
+	delta /= 125;
+
+	*scaled_ppm = delta;
+
+	return 0;
+}
+
 static int mlx5_ptp_adjfreq_real_time(struct mlx5_core_dev *mdev, s32 freq)
 {
 	u32 in[MLX5_ST_SZ_DW(mtutc_reg)] = {};
@@ -688,6 +722,7 @@ static const struct ptp_clock_info mlx5_ptp_clock_info = {
 	.n_pins		= 0,
 	.pps		= 0,
 	.adjfine	= mlx5_ptp_adjfine,
+	.getfine	= mlx5_ptp_getfine,
 	.adjtime	= mlx5_ptp_adjtime,
 	.gettimex64	= mlx5_ptp_gettimex,
 	.settime64	= mlx5_ptp_settime,
-- 
2.36.2