ptp_qoriq: fix latency in ptp_qoriq_adjtime() operation

1588 driver loses about 1us in adjtime operation at PTP slave
This is because adjtime operation uses a slow non-atomic tmr_cnt_read()
followed by tmr_cnt_write() operation.

In the above sequence, since the timer counter operation keeps
incrementing, it leads to latency. The tmr_offset register
(which is added to TMR_CNT_H/L register giving the current time)
must be programmed with the delta nanoseconds.

Signed-off-by: Nikhil Gupta <nikhil.gupta@nxp.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Tested-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/20230119204034.7969-1-nikhil.gupta@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/ptp/ptp_qoriq.c b/drivers/ptp/ptp_qoriq.c
index 08f4cf0..6153016 100644 (file)
--- a/drivers/ptp/ptp_qoriq.c
+++ b/drivers/ptp/ptp_qoriq.c
@@ -48,6 +48,29 @@ static void tmr_cnt_write(struct ptp_qoriq *ptp_qoriq, u64 ns)
        ptp_qoriq->write(&regs->ctrl_regs->tmr_cnt_h, hi);
 }
 
+static u64 tmr_offset_read(struct ptp_qoriq *ptp_qoriq)
+{
+       struct ptp_qoriq_registers *regs = &ptp_qoriq->regs;
+       u32 lo, hi;
+       u64 ns;
+
+       lo = ptp_qoriq->read(&regs->ctrl_regs->tmroff_l);
+       hi = ptp_qoriq->read(&regs->ctrl_regs->tmroff_h);
+       ns = ((u64) hi) << 32;
+       ns |= lo;
+       return ns;
+}
+
+static void tmr_offset_write(struct ptp_qoriq *ptp_qoriq, u64 delta_ns)
+{
+       struct ptp_qoriq_registers *regs = &ptp_qoriq->regs;
+       u32 lo = delta_ns & 0xffffffff;
+       u32 hi = delta_ns >> 32;
+
+       ptp_qoriq->write(&regs->ctrl_regs->tmroff_l, lo);
+       ptp_qoriq->write(&regs->ctrl_regs->tmroff_h, hi);
+}
+
 /* Caller must hold ptp_qoriq->lock. */
 static void set_alarm(struct ptp_qoriq *ptp_qoriq)
 {
@@ -55,7 +78,9 @@ static void set_alarm(struct ptp_qoriq *ptp_qoriq)
        u64 ns;
        u32 lo, hi;
 
-       ns = tmr_cnt_read(ptp_qoriq) + 1500000000ULL;
+       ns = tmr_cnt_read(ptp_qoriq) + tmr_offset_read(ptp_qoriq)
+                                    + 1500000000ULL;
+
        ns = div_u64(ns, 1000000000UL) * 1000000000ULL;
        ns -= ptp_qoriq->tclk_period;
        hi = ns >> 32;
@@ -207,15 +232,24 @@ EXPORT_SYMBOL_GPL(ptp_qoriq_adjfine);
 
 int ptp_qoriq_adjtime(struct ptp_clock_info *ptp, s64 delta)
 {
-       s64 now;
-       unsigned long flags;
        struct ptp_qoriq *ptp_qoriq = container_of(ptp, struct ptp_qoriq, caps);
+       s64 now, curr_delta;
+       unsigned long flags;
 
        spin_lock_irqsave(&ptp_qoriq->lock, flags);
 
-       now = tmr_cnt_read(ptp_qoriq);
-       now += delta;
-       tmr_cnt_write(ptp_qoriq, now);
+       /* On LS1021A, eTSEC2 and eTSEC3 do not take into account the TMR_OFF
+        * adjustment
+        */
+       if (ptp_qoriq->etsec) {
+               now = tmr_cnt_read(ptp_qoriq);
+               now += delta;
+               tmr_cnt_write(ptp_qoriq, now);
+       } else {
+               curr_delta = tmr_offset_read(ptp_qoriq);
+               curr_delta += delta;
+               tmr_offset_write(ptp_qoriq, curr_delta);
+       }
        set_fipers(ptp_qoriq);
 
        spin_unlock_irqrestore(&ptp_qoriq->lock, flags);
@@ -232,7 +266,7 @@ int ptp_qoriq_gettime(struct ptp_clock_info *ptp, struct timespec64 *ts)
 
        spin_lock_irqsave(&ptp_qoriq->lock, flags);
 
-       ns = tmr_cnt_read(ptp_qoriq);
+       ns = tmr_cnt_read(ptp_qoriq) + tmr_offset_read(ptp_qoriq);
 
        spin_unlock_irqrestore(&ptp_qoriq->lock, flags);
 
@@ -253,6 +287,7 @@ int ptp_qoriq_settime(struct ptp_clock_info *ptp,
 
        spin_lock_irqsave(&ptp_qoriq->lock, flags);
 
+       tmr_offset_write(ptp_qoriq, 0);
        tmr_cnt_write(ptp_qoriq, ns);
        set_fipers(ptp_qoriq);
 
@@ -488,6 +523,7 @@ int ptp_qoriq_init(struct ptp_qoriq *ptp_qoriq, void __iomem *base,
 
        /* The eTSEC uses differnt memory map with DPAA/ENETC */
        if (of_device_is_compatible(node, "fsl,etsec-ptp")) {
+               ptp_qoriq->etsec = true;
                ptp_qoriq->regs.ctrl_regs = base + ETSEC_CTRL_REGS_OFFSET;
                ptp_qoriq->regs.alarm_regs = base + ETSEC_ALARM_REGS_OFFSET;
                ptp_qoriq->regs.fiper_regs = base + ETSEC_FIPER_REGS_OFFSET;

diff --git a/include/linux/fsl/ptp_qoriq.h b/include/linux/fsl/ptp_qoriq.h
index 01acebe..b301bf7 100644 (file)
--- a/include/linux/fsl/ptp_qoriq.h
+++ b/include/linux/fsl/ptp_qoriq.h
@@ -149,6 +149,7 @@ struct ptp_qoriq {
        struct device *dev;
        bool extts_fifo_support;
        bool fiper3_support;
+       bool etsec;
        int irq;
        int phc_index;
        u32 tclk_period;  /* nanoseconds */