netdev - [PATCH v1 2/4] net: fec: ptp: Use hardware algorithm to adjust PTP counter.

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Message-ID: <1411632621-17429-3-git-send-email-b45643@freescale.com>
Date:	Thu, 25 Sep 2014 16:10:19 +0800
From:	Luwei Zhou <b45643@...escale.com>
To:	<davem@...emloft.net>, <richardcochran@...il.com>
CC:	<netdev@...r.kernel.org>, <shawn.guo@...aro.org>,
	<bhutchings@...arflare.com>, <R49496@...escale.com>,
	<b38611@...escale.com>, <b20596@...escale.com>,
	<stephen@...workplumber.org>
Subject: [PATCH v1 2/4] net: fec: ptp: Use hardware algorithm to adjust PTP counter.

The FEC IP supports hardware adjustment for ptp timer. Refer to the description of
ENET_ATCOR and ENET_ATINC registers in the spec about the hardware adjustment. This
patch uses hardware support to adjust the ptp offset and frequency on the slave side.

Signed-off-by: Luwei Zhou <b45643@...escale.com>
Signed-off-by: Frank Li <Frank.Li@...escale.com>
Signed-off-by: Fugang Duan <b38611@...escale.com>
---
 drivers/net/ethernet/freescale/fec_ptp.c | 68 +++++++++++++++++++++++++++-----
 1 file changed, 58 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec_ptp.c b/drivers/net/ethernet/freescale/fec_ptp.c
index 8016bdd..e2bf786 100644
--- a/drivers/net/ethernet/freescale/fec_ptp.c
+++ b/drivers/net/ethernet/freescale/fec_ptp.c
@@ -71,6 +71,7 @@
 
 #define FEC_CC_MULT	(1 << 31)
 #define FEC_COUNTER_PERIOD	(1 << 31)
+#define FEC_T_PERIOD_ONE_SEC	(1000000000UL)
 /**
  * fec_ptp_read - read raw cycle counter (to be used by time counter)
  * @cc: the cyclecounter structure
@@ -145,33 +146,65 @@ void fec_ptp_start_cyclecounter(struct net_device *ndev)
  */
 static int fec_ptp_adjfreq(struct ptp_clock_info *ptp, s32 ppb)
 {
-	u64 diff;
 	unsigned long flags;
 	int neg_adj = 0;
-	u32 mult = FEC_CC_MULT;
+	u32 i, tmp;
+	u32 ptp_ts_clk, ptp_inc;
+	u32 corr_inc, corr_period;
+	u32 corr_ns;
 
 	struct fec_enet_private *fep =
 	    container_of(ptp, struct fec_enet_private, ptp_caps);
 
+	if (ppb == 0)
+		return 0;
+
 	if (ppb < 0) {
 		ppb = -ppb;
 		neg_adj = 1;
 	}
 
-	diff = mult;
-	diff *= ppb;
-	diff = div_u64(diff, 1000000000ULL);
+	ptp_ts_clk = clk_get_rate(fep->clk_ptp);
+	ptp_inc = FEC_T_PERIOD_ONE_SEC / ptp_ts_clk;
+
+	/*
+	 * In theory, corr_inc/corr_period = ppb/FEC_T_PERIOD_ONE_SEC;
+	 * Try to find the corr_inc  between 1 to ptp_inc to meet adjustment
+	 * requirement.
+	 */
+	for (i = 1; i <= ptp_inc; i++) {
+		if (((i * FEC_T_PERIOD_ONE_SEC) / ppb) >= ptp_inc) {
+			corr_inc = i;
+			corr_period = ((i * FEC_T_PERIOD_ONE_SEC) /
+						(ptp_inc * ppb));
+			break;
+		}
+	}
+	/*
+	 * Not found? Set it to high value - double speed
+	 * correct in every clock step.
+	 */
+	if (i > ptp_inc) {
+		corr_inc = ptp_inc;
+		corr_period = 1;
+	}
+
+	if (neg_adj)
+		corr_ns = ptp_inc - corr_inc;
+	else
+		corr_ns = ptp_inc + corr_inc;
 
 	spin_lock_irqsave(&fep->tmreg_lock, flags);
+
+	tmp = readl(fep->hwp + FEC_ATIME_INC) & FEC_T_INC_MASK;
+	tmp |= corr_ns << FEC_T_INC_CORR_OFFSET;
+	writel(tmp, fep->hwp + FEC_ATIME_INC);
+	writel(corr_period, fep->hwp + FEC_ATIME_CORR);
 	/*
-	 * dummy read to set cycle_last in tc to now.
-	 * So use adjusted mult to calculate when next call
-	 * timercounter_read.
+	 * dummy read to update the timer.
 	 */
 	timecounter_read(&fep->tc);
 
-	fep->cc.mult = neg_adj ? mult - diff : mult + diff;
-
 	spin_unlock_irqrestore(&fep->tmreg_lock, flags);
 
 	return 0;
@@ -190,12 +223,20 @@ static int fec_ptp_adjtime(struct ptp_clock_info *ptp, s64 delta)
 	    container_of(ptp, struct fec_enet_private, ptp_caps);
 	unsigned long flags;
 	u64 now;
+	u32 counter;
 
 	spin_lock_irqsave(&fep->tmreg_lock, flags);
 
 	now = timecounter_read(&fep->tc);
 	now += delta;
 
+	/*
+	 * Get the timer value based on adjusted timestamp.
+	 * Update the counter with the masked value.
+	 */
+	counter = now & fep->cc.mask;
+	writel(counter, fep->hwp + FEC_ATIME);
+
 	/* reset the timecounter */
 	timecounter_init(&fep->tc, &fep->cc, now);
 
@@ -246,6 +287,7 @@ static int fec_ptp_settime(struct ptp_clock_info *ptp,
 
 	u64 ns;
 	unsigned long flags;
+	u32 counter;
 
 	mutex_lock(&fep->ptp_clk_mutex);
 	/* Check the ptp clock */
@@ -256,8 +298,14 @@ static int fec_ptp_settime(struct ptp_clock_info *ptp,
 
 	ns = ts->tv_sec * 1000000000ULL;
 	ns += ts->tv_nsec;
+	/*
+	 * Get the timer value based on timestamp.
+	 * Update the counter with the masked value.
+	 */
+	counter = ns & fep->cc.mask;
 
 	spin_lock_irqsave(&fep->tmreg_lock, flags);
+	writel(counter, fep->hwp + FEC_ATIME);
 	timecounter_init(&fep->tc, &fep->cc, ns);
 	spin_unlock_irqrestore(&fep->tmreg_lock, flags);
 	mutex_unlock(&fep->ptp_clk_mutex);
-- 
1.9.1

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