2022-12-06 09:46:08

by Arun Ramadoss

[permalink] [raw]
Subject: [Patch net-next v2 01/13] net: dsa: microchip: ptp: add the posix clock support

From: Christian Eggers <[email protected]>

This patch implement routines (adjfine, adjtime, gettime and settime)
for manipulating the chip's PTP clock. It registers the ptp caps
to posix clock register.

Signed-off-by: Christian Eggers <[email protected]>
Co-developed-by: Arun Ramadoss <[email protected]>
Signed-off-by: Arun Ramadoss <[email protected]>

---
v1 -> v2
- added arri in copyright message
- Deleted setting 8021_1as bit and added P2P bit in ksz_ptp_clock_register()
- Renamed error_return label to unlock
- Assigned the ptp_clock_info directly instead of const struct
- moved the semicolon in ksz_rmw16 after 0x%x:
- moved ts_info to next patch

RFC v2 -> Patch v1
- Repharsed the Kconfig help text
- Removed IS_ERR_OR_NULL check in ptp_clock_unregister
- Add the check for ptp_data->clock in ksz_ptp_ts_info
- Renamed MAX_DRIFT_CORR to KSZ_MAX_DRIFT_CORR
- Removed the comments
- Variables declaration in reverse christmas tree
- Added the ptp_clock_optional
---
drivers/net/dsa/microchip/Kconfig | 11 ++
drivers/net/dsa/microchip/Makefile | 5 +
drivers/net/dsa/microchip/ksz_common.c | 13 +-
drivers/net/dsa/microchip/ksz_common.h | 16 ++
drivers/net/dsa/microchip/ksz_ptp.c | 237 ++++++++++++++++++++++++
drivers/net/dsa/microchip/ksz_ptp.h | 42 +++++
drivers/net/dsa/microchip/ksz_ptp_reg.h | 52 ++++++
7 files changed, 375 insertions(+), 1 deletion(-)
create mode 100644 drivers/net/dsa/microchip/ksz_ptp.c
create mode 100644 drivers/net/dsa/microchip/ksz_ptp.h
create mode 100644 drivers/net/dsa/microchip/ksz_ptp_reg.h

diff --git a/drivers/net/dsa/microchip/Kconfig b/drivers/net/dsa/microchip/Kconfig
index 913f83ef013c..0546c573668a 100644
--- a/drivers/net/dsa/microchip/Kconfig
+++ b/drivers/net/dsa/microchip/Kconfig
@@ -11,6 +11,7 @@ menuconfig NET_DSA_MICROCHIP_KSZ_COMMON
config NET_DSA_MICROCHIP_KSZ9477_I2C
tristate "KSZ series I2C connected switch driver"
depends on NET_DSA_MICROCHIP_KSZ_COMMON && I2C
+ depends on PTP_1588_CLOCK_OPTIONAL
select REGMAP_I2C
help
Select to enable support for registering switches configured through I2C.
@@ -18,10 +19,20 @@ config NET_DSA_MICROCHIP_KSZ9477_I2C
config NET_DSA_MICROCHIP_KSZ_SPI
tristate "KSZ series SPI connected switch driver"
depends on NET_DSA_MICROCHIP_KSZ_COMMON && SPI
+ depends on PTP_1588_CLOCK_OPTIONAL
select REGMAP_SPI
help
Select to enable support for registering switches configured through SPI.

+config NET_DSA_MICROCHIP_KSZ_PTP
+ bool "Support for the PTP clock on the KSZ9563/LAN937x Ethernet Switch"
+ depends on NET_DSA_MICROCHIP_KSZ_COMMON && PTP_1588_CLOCK
+ help
+ Select to enable support for timestamping & PTP clock manipulation in
+ KSZ8563/KSZ9563/LAN937x series of switches. KSZ9563/KSZ8563 supports
+ only one step timestamping. LAN937x switch supports both one step and
+ two step timestamping.
+
config NET_DSA_MICROCHIP_KSZ8863_SMI
tristate "KSZ series SMI connected switch driver"
depends on NET_DSA_MICROCHIP_KSZ_COMMON
diff --git a/drivers/net/dsa/microchip/Makefile b/drivers/net/dsa/microchip/Makefile
index 28873559efc2..48360cc9fc68 100644
--- a/drivers/net/dsa/microchip/Makefile
+++ b/drivers/net/dsa/microchip/Makefile
@@ -4,6 +4,11 @@ ksz_switch-objs := ksz_common.o
ksz_switch-objs += ksz9477.o
ksz_switch-objs += ksz8795.o
ksz_switch-objs += lan937x_main.o
+
+ifdef CONFIG_NET_DSA_MICROCHIP_KSZ_PTP
+ksz_switch-objs += ksz_ptp.o
+endif
+
obj-$(CONFIG_NET_DSA_MICROCHIP_KSZ9477_I2C) += ksz9477_i2c.o
obj-$(CONFIG_NET_DSA_MICROCHIP_KSZ_SPI) += ksz_spi.o
obj-$(CONFIG_NET_DSA_MICROCHIP_KSZ8863_SMI) += ksz8863_smi.o
diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c
index 8c8db315317d..da717feca30a 100644
--- a/drivers/net/dsa/microchip/ksz_common.c
+++ b/drivers/net/dsa/microchip/ksz_common.c
@@ -24,6 +24,7 @@
#include <net/switchdev.h>

#include "ksz_common.h"
+#include "ksz_ptp.h"
#include "ksz8.h"
#include "ksz9477.h"
#include "lan937x.h"
@@ -2016,10 +2017,16 @@ static int ksz_setup(struct dsa_switch *ds)
}
}

+ ret = ksz_ptp_clock_register(ds);
+ if (ret) {
+ dev_err(dev->dev, "Failed to register PTP clock: %d\n", ret);
+ goto out_pirq;
+ }
+
ret = ksz_mdio_register(dev);
if (ret < 0) {
dev_err(dev->dev, "failed to register the mdio");
- goto out_pirq;
+ goto out_ptp_clock_unregister;
}

/* start switch */
@@ -2028,6 +2035,8 @@ static int ksz_setup(struct dsa_switch *ds)

return 0;

+out_ptp_clock_unregister:
+ ksz_ptp_clock_unregister(ds);
out_pirq:
if (dev->irq > 0)
dsa_switch_for_each_user_port(dp, dev->ds)
@@ -2044,6 +2053,8 @@ static void ksz_teardown(struct dsa_switch *ds)
struct ksz_device *dev = ds->priv;
struct dsa_port *dp;

+ ksz_ptp_clock_unregister(ds);
+
if (dev->irq > 0) {
dsa_switch_for_each_user_port(dp, dev->ds)
ksz_irq_free(&dev->ports[dp->index].pirq);
diff --git a/drivers/net/dsa/microchip/ksz_common.h b/drivers/net/dsa/microchip/ksz_common.h
index c6726cbd5465..78b4101553c6 100644
--- a/drivers/net/dsa/microchip/ksz_common.h
+++ b/drivers/net/dsa/microchip/ksz_common.h
@@ -15,6 +15,8 @@
#include <net/dsa.h>
#include <linux/irq.h>

+#include "ksz_ptp.h"
+
#define KSZ_MAX_NUM_PORTS 8

struct ksz_device;
@@ -141,6 +143,7 @@ struct ksz_device {
u16 port_mask;
struct mutex lock_irq; /* IRQ Access */
struct ksz_irq girq;
+ struct ksz_ptp_data ptp_data;
};

/* List of supported models */
@@ -444,6 +447,19 @@ static inline int ksz_write32(struct ksz_device *dev, u32 reg, u32 value)
return ret;
}

+static inline int ksz_rmw16(struct ksz_device *dev, u32 reg, u16 mask,
+ u16 value)
+{
+ int ret;
+
+ ret = regmap_update_bits(dev->regmap[1], reg, mask, value);
+ if (ret)
+ dev_err(dev->dev, "can't rmw 16bit reg 0x%x: %pe\n", reg,
+ ERR_PTR(ret));
+
+ return ret;
+}
+
static inline int ksz_write64(struct ksz_device *dev, u32 reg, u64 value)
{
u32 val[2];
diff --git a/drivers/net/dsa/microchip/ksz_ptp.c b/drivers/net/dsa/microchip/ksz_ptp.c
new file mode 100644
index 000000000000..68b1770da6ca
--- /dev/null
+++ b/drivers/net/dsa/microchip/ksz_ptp.c
@@ -0,0 +1,237 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Microchip KSZ PTP Implementation
+ *
+ * Copyright (C) 2020 ARRI Lighting
+ * Copyright (C) 2022 Microchip Technology Inc.
+ */
+
+#include <linux/kernel.h>
+#include <linux/ptp_classify.h>
+#include <linux/ptp_clock_kernel.h>
+
+#include "ksz_common.h"
+#include "ksz_ptp.h"
+#include "ksz_ptp_reg.h"
+
+#define ptp_caps_to_data(d) container_of((d), struct ksz_ptp_data, caps)
+#define ptp_data_to_ksz_dev(d) container_of((d), struct ksz_device, ptp_data)
+
+/* Sub-nanoseconds-adj,max * sub-nanoseconds / 40ns * 1ns
+ * = (2^30-1) * (2 ^ 32) / 40 ns * 1 ns = 6249999
+ */
+#define KSZ_MAX_DRIFT_CORR 6249999
+
+#define KSZ_PTP_INC_NS 40 /* HW clock is incremented every 40 ns (by 40) */
+#define KSZ_PTP_SUBNS_BITS 32
+
+static int _ksz_ptp_gettime(struct ksz_device *dev, struct timespec64 *ts)
+{
+ u32 nanoseconds;
+ u32 seconds;
+ u8 phase;
+ int ret;
+
+ /* Copy current PTP clock into shadow registers and read */
+ ret = ksz_rmw16(dev, REG_PTP_CLK_CTRL, PTP_READ_TIME, PTP_READ_TIME);
+ if (ret)
+ return ret;
+
+ ret = ksz_read8(dev, REG_PTP_RTC_SUB_NANOSEC__2, &phase);
+ if (ret)
+ return ret;
+
+ ret = ksz_read32(dev, REG_PTP_RTC_NANOSEC, &nanoseconds);
+ if (ret)
+ return ret;
+
+ ret = ksz_read32(dev, REG_PTP_RTC_SEC, &seconds);
+ if (ret)
+ return ret;
+
+ ts->tv_sec = seconds;
+ ts->tv_nsec = nanoseconds + phase * 8;
+
+ return 0;
+}
+
+static int ksz_ptp_gettime(struct ptp_clock_info *ptp, struct timespec64 *ts)
+{
+ struct ksz_ptp_data *ptp_data = ptp_caps_to_data(ptp);
+ struct ksz_device *dev = ptp_data_to_ksz_dev(ptp_data);
+ int ret;
+
+ mutex_lock(&ptp_data->lock);
+ ret = _ksz_ptp_gettime(dev, ts);
+ mutex_unlock(&ptp_data->lock);
+
+ return ret;
+}
+
+static int ksz_ptp_settime(struct ptp_clock_info *ptp,
+ const struct timespec64 *ts)
+{
+ struct ksz_ptp_data *ptp_data = ptp_caps_to_data(ptp);
+ struct ksz_device *dev = ptp_data_to_ksz_dev(ptp_data);
+ int ret;
+
+ mutex_lock(&ptp_data->lock);
+
+ /* Write to shadow registers and Load PTP clock */
+ ret = ksz_write16(dev, REG_PTP_RTC_SUB_NANOSEC__2, PTP_RTC_0NS);
+ if (ret)
+ goto unlock;
+
+ ret = ksz_write32(dev, REG_PTP_RTC_NANOSEC, ts->tv_nsec);
+ if (ret)
+ goto unlock;
+
+ ret = ksz_write32(dev, REG_PTP_RTC_SEC, ts->tv_sec);
+ if (ret)
+ goto unlock;
+
+ ret = ksz_rmw16(dev, REG_PTP_CLK_CTRL, PTP_LOAD_TIME, PTP_LOAD_TIME);
+
+unlock:
+ mutex_unlock(&ptp_data->lock);
+
+ return ret;
+}
+
+static int ksz_ptp_adjfine(struct ptp_clock_info *ptp, long scaled_ppm)
+{
+ struct ksz_ptp_data *ptp_data = ptp_caps_to_data(ptp);
+ struct ksz_device *dev = ptp_data_to_ksz_dev(ptp_data);
+ int ret;
+
+ mutex_lock(&ptp_data->lock);
+
+ if (scaled_ppm) {
+ s64 ppb, adj;
+ u32 data32;
+
+ /* see scaled_ppm_to_ppb() in ptp_clock.c for details */
+ ppb = 1 + scaled_ppm;
+ ppb *= 125;
+ ppb *= KSZ_PTP_INC_NS;
+ ppb <<= KSZ_PTP_SUBNS_BITS - 13;
+ adj = div_s64(ppb, NSEC_PER_SEC);
+
+ data32 = abs(adj);
+ data32 &= PTP_SUBNANOSEC_M;
+ if (adj >= 0)
+ data32 |= PTP_RATE_DIR;
+
+ ret = ksz_write32(dev, REG_PTP_SUBNANOSEC_RATE, data32);
+ if (ret)
+ goto unlock;
+
+ ret = ksz_rmw16(dev, REG_PTP_CLK_CTRL, PTP_CLK_ADJ_ENABLE,
+ PTP_CLK_ADJ_ENABLE);
+ if (ret)
+ goto unlock;
+ } else {
+ ret = ksz_rmw16(dev, REG_PTP_CLK_CTRL, PTP_CLK_ADJ_ENABLE, 0);
+ if (ret)
+ goto unlock;
+ }
+
+unlock:
+ mutex_unlock(&ptp_data->lock);
+ return ret;
+}
+
+static int ksz_ptp_adjtime(struct ptp_clock_info *ptp, s64 delta)
+{
+ struct ksz_ptp_data *ptp_data = ptp_caps_to_data(ptp);
+ struct ksz_device *dev = ptp_data_to_ksz_dev(ptp_data);
+ s32 sec, nsec;
+ u16 data16;
+ int ret;
+
+ mutex_lock(&ptp_data->lock);
+
+ /* do not use ns_to_timespec64(),
+ * both sec and nsec are subtracted by hw
+ */
+ sec = div_s64_rem(delta, NSEC_PER_SEC, &nsec);
+
+ ret = ksz_write32(dev, REG_PTP_RTC_NANOSEC, abs(nsec));
+ if (ret)
+ goto unlock;
+
+ ret = ksz_write32(dev, REG_PTP_RTC_SEC, abs(sec));
+ if (ret)
+ goto unlock;
+
+ ret = ksz_read16(dev, REG_PTP_CLK_CTRL, &data16);
+ if (ret)
+ goto unlock;
+
+ data16 |= PTP_STEP_ADJ;
+
+ /* PTP_STEP_DIR -- 0: subtract, 1: add */
+ if (delta < 0)
+ data16 &= ~PTP_STEP_DIR;
+ else
+ data16 |= PTP_STEP_DIR;
+
+ ret = ksz_write16(dev, REG_PTP_CLK_CTRL, data16);
+
+unlock:
+ mutex_unlock(&ptp_data->lock);
+ return ret;
+}
+
+static int ksz_ptp_start_clock(struct ksz_device *dev)
+{
+ return ksz_rmw16(dev, REG_PTP_CLK_CTRL, PTP_CLK_ENABLE, PTP_CLK_ENABLE);
+}
+
+int ksz_ptp_clock_register(struct dsa_switch *ds)
+{
+ struct ksz_device *dev = ds->priv;
+ struct ksz_ptp_data *ptp_data;
+ int ret;
+
+ ptp_data = &dev->ptp_data;
+ mutex_init(&ptp_data->lock);
+
+ ptp_data->caps.owner = THIS_MODULE;
+ snprintf(ptp_data->caps.name, 16, "Microchip Clock");
+ ptp_data->caps.max_adj = KSZ_MAX_DRIFT_CORR;
+ ptp_data->caps.gettime64 = ksz_ptp_gettime;
+ ptp_data->caps.settime64 = ksz_ptp_settime;
+ ptp_data->caps.adjfine = ksz_ptp_adjfine;
+ ptp_data->caps.adjtime = ksz_ptp_adjtime;
+
+ ret = ksz_ptp_start_clock(dev);
+ if (ret)
+ return ret;
+
+ /* Currently only P2P mode is supported */
+ ret = ksz_rmw16(dev, REG_PTP_MSG_CONF1, PTP_TC_P2P, PTP_TC_P2P);
+ if (ret)
+ return ret;
+
+ ptp_data->clock = ptp_clock_register(&ptp_data->caps, dev->dev);
+ if (IS_ERR_OR_NULL(ptp_data->clock))
+ return PTR_ERR(ptp_data->clock);
+
+ return 0;
+}
+
+void ksz_ptp_clock_unregister(struct dsa_switch *ds)
+{
+ struct ksz_device *dev = ds->priv;
+ struct ksz_ptp_data *ptp_data;
+
+ ptp_data = &dev->ptp_data;
+
+ if (ptp_data->clock)
+ ptp_clock_unregister(ptp_data->clock);
+}
+
+MODULE_AUTHOR("Christian Eggers <[email protected]>");
+MODULE_AUTHOR("Arun Ramadoss <[email protected]>");
+MODULE_DESCRIPTION("PTP support for KSZ switch");
+MODULE_LICENSE("GPL");
diff --git a/drivers/net/dsa/microchip/ksz_ptp.h b/drivers/net/dsa/microchip/ksz_ptp.h
new file mode 100644
index 000000000000..8930047da764
--- /dev/null
+++ b/drivers/net/dsa/microchip/ksz_ptp.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Microchip KSZ PTP Implementation
+ *
+ * Copyright (C) 2020 ARRI Lighting
+ * Copyright (C) 2022 Microchip Technology Inc.
+ */
+
+#ifndef _NET_DSA_DRIVERS_KSZ_PTP_H
+#define _NET_DSA_DRIVERS_KSZ_PTP_H
+
+#if IS_ENABLED(CONFIG_NET_DSA_MICROCHIP_KSZ_PTP)
+
+#include <linux/ptp_clock_kernel.h>
+
+struct ksz_ptp_data {
+ struct ptp_clock_info caps;
+ struct ptp_clock *clock;
+ /* Serializes all operations on the PTP hardware clock */
+ struct mutex lock;
+};
+
+int ksz_ptp_clock_register(struct dsa_switch *ds);
+
+void ksz_ptp_clock_unregister(struct dsa_switch *ds);
+
+#else
+
+struct ksz_ptp_data {
+ /* Serializes all operations on the PTP hardware clock */
+ struct mutex lock;
+};
+
+static inline int ksz_ptp_clock_register(struct dsa_switch *ds)
+{
+ return 0;
+}
+
+static inline void ksz_ptp_clock_unregister(struct dsa_switch *ds) { }
+
+#endif /* End of CONFIG_NET_DSA_MICROCHIP_KSZ_PTP */
+
+#endif
diff --git a/drivers/net/dsa/microchip/ksz_ptp_reg.h b/drivers/net/dsa/microchip/ksz_ptp_reg.h
new file mode 100644
index 000000000000..4ca4ad4bba7e
--- /dev/null
+++ b/drivers/net/dsa/microchip/ksz_ptp_reg.h
@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Microchip KSZ PTP register definitions
+ * Copyright (C) 2022 Microchip Technology Inc.
+ */
+
+#ifndef __KSZ_PTP_REGS_H
+#define __KSZ_PTP_REGS_H
+
+/* 5 - PTP Clock */
+#define REG_PTP_CLK_CTRL 0x0500
+
+#define PTP_STEP_ADJ BIT(6)
+#define PTP_STEP_DIR BIT(5)
+#define PTP_READ_TIME BIT(4)
+#define PTP_LOAD_TIME BIT(3)
+#define PTP_CLK_ADJ_ENABLE BIT(2)
+#define PTP_CLK_ENABLE BIT(1)
+#define PTP_CLK_RESET BIT(0)
+
+#define REG_PTP_RTC_SUB_NANOSEC__2 0x0502
+
+#define PTP_RTC_SUB_NANOSEC_M 0x0007
+#define PTP_RTC_0NS 0x00
+
+#define REG_PTP_RTC_NANOSEC 0x0504
+
+#define REG_PTP_RTC_SEC 0x0508
+
+#define REG_PTP_SUBNANOSEC_RATE 0x050C
+
+#define PTP_SUBNANOSEC_M 0x3FFFFFFF
+#define PTP_RATE_DIR BIT(31)
+#define PTP_TMP_RATE_ENABLE BIT(30)
+
+#define REG_PTP_SUBNANOSEC_RATE_L 0x050E
+
+#define REG_PTP_RATE_DURATION 0x0510
+#define REG_PTP_RATE_DURATION_H 0x0510
+#define REG_PTP_RATE_DURATION_L 0x0512
+
+#define REG_PTP_MSG_CONF1 0x0514
+
+#define PTP_802_1AS BIT(7)
+#define PTP_ENABLE BIT(6)
+#define PTP_ETH_ENABLE BIT(5)
+#define PTP_IPV4_UDP_ENABLE BIT(4)
+#define PTP_IPV6_UDP_ENABLE BIT(3)
+#define PTP_TC_P2P BIT(2)
+#define PTP_MASTER BIT(1)
+#define PTP_1STEP BIT(0)
+
+#endif
--
2.36.1


2022-12-06 10:47:47

by Christian Eggers

[permalink] [raw]
Subject: Re: [Patch net-next v2 01/13] net: dsa: microchip: ptp: add the posix clock support

Hi Arun,

On Tuesday, 6 December 2022, 10:14:16 CET, Arun Ramadoss wrote:
> From: Christian Eggers <[email protected]>
>
> This patch implement routines (adjfine, adjtime, gettime and settime)
> for manipulating the chip's PTP clock. It registers the ptp caps
> to posix clock register.
>
> Signed-off-by: Christian Eggers <[email protected]>
> Co-developed-by: Arun Ramadoss <[email protected]>
> Signed-off-by: Arun Ramadoss <[email protected]>
>
> ---
> v1 -> v2
> - added arri in copyright message
> - Deleted setting 8021_1as bit and added P2P bit in ksz_ptp_clock_register()

did I miss the discussion about this change? I thought that the first goal is
to use KSZ switches as a boundary clock which implies using the 802.1AS feature.

Using the KSZ in P2P transparent clock mode IMHO requires writing the peer delays
into switch registers (which needs to be implemented in a companion
application/script for ptp4p).

As far as I remember, there is also no support using ptp4l with 1-step transparent
clock switches.

regards
Christian




2022-12-06 11:05:23

by Vladimir Oltean

[permalink] [raw]
Subject: Re: [Patch net-next v2 01/13] net: dsa: microchip: ptp: add the posix clock support

On Tue, Dec 06, 2022 at 11:37:26AM +0100, Christian Eggers wrote:
> > v1 -> v2
> > - Deleted setting 8021_1as bit and added P2P bit in ksz_ptp_clock_register()
>
> did I miss the discussion about this change? I thought that the first goal is
> to use KSZ switches as a boundary clock which implies using the 802.1AS feature.
>
> Using the KSZ in P2P transparent clock mode IMHO requires writing the peer delays
> into switch registers (which needs to be implemented in a companion
> application/script for ptp4p).
>
> As far as I remember, there is also no support using ptp4l with 1-step transparent
> clock switches.

If it was in response to something I said, I just asked to add a comment
as to what the 802.1AS bit does, not to delete it...

2022-12-07 04:42:45

by Arun Ramadoss

[permalink] [raw]
Subject: Re: [Patch net-next v2 01/13] net: dsa: microchip: ptp: add the posix clock support

Hi Vladimir,
On Tue, 2022-12-06 at 12:48 +0200, Vladimir Oltean wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you
> know the content is safe
>
> On Tue, Dec 06, 2022 at 11:37:26AM +0100, Christian Eggers wrote:
> > > v1 -> v2
> > > - Deleted setting 8021_1as bit and added P2P bit in
> > > ksz_ptp_clock_register()
> >
> > did I miss the discussion about this change? I thought that the
> > first goal is
> > to use KSZ switches as a boundary clock which implies using the
> > 802.1AS feature.
> >
> > Using the KSZ in P2P transparent clock mode IMHO requires writing
> > the peer delays
> > into switch registers (which needs to be implemented in a companion
> > application/script for ptp4p).
> >
> > As far as I remember, there is also no support using ptp4l with 1-
> > step transparent
> > clock switches.
>
> If it was in response to something I said, I just asked to add a
> comment
> as to what the 802.1AS bit does, not to delete it...

I got confused with the review comments like Is this bit required for
p2p 1 step timestamping and also because this bit is mentioned reserved
in datasheet for KSZ9563.
When the 802.1AS bit is set in PTP_MSG_CONF1 register, it forwards all
the PTP frames to cpu port and not to other ports.
Since, the 2 step timestamping does not work in KSZ9563, this bit is
made as reserved in the datasheet.
I will revert the changes back to setting 802.1AS bit and add
appropriate comment in the code/commit description.