Messages in this thread Patch in this message | | | From | Nikhil Gupta <> | Subject | RE: [PATCH] ptp_qoriq: fix latency in ptp_qoriq_adjtime() operation. | Date | Tue, 10 Jan 2023 11:53:43 +0000 |
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++ Richard Cochran
-----Original Message----- From: nikhil.gupta@nxp.com <nikhil.gupta@nxp.com> Sent: Tuesday, January 10, 2023 5:00 PM To: linux-arm-kernel@lists.infradead.org; Y.B. Lu <yangbo.lu@nxp.com>; netdev@vger.kernel.org; linux-kernel@vger.kernel.org Cc: Vakul Garg <vakul.garg@nxp.com>; Rajan Gupta <rajan.gupta@nxp.com>; Nikhil Gupta <nikhil.gupta@nxp.com> Subject: [PATCH] ptp_qoriq: fix latency in ptp_qoriq_adjtime() operation.
From: Nikhil Gupta <nikhil.gupta@nxp.com>
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 loses about 1us. Instead, tmr_offset register should be programmed with the delta nanoseconds This won't lead to timer counter stopping and losing time while tmr_cnt_write() is being done. This Patch adds api for tmr_offset_read/write to program the delta nanoseconds in the Timer offset Register.
Signed-off-by: Nikhil Gupta <nikhil.gupta@nxp.com> Reviewed-by: Yangbo Lu <yangbo.lu@nxp.com> --- drivers/ptp/ptp_qoriq.c | 36 ++++++++++++++++++++++++++++++------ 1 file changed, 30 insertions(+), 6 deletions(-)
diff --git a/drivers/ptp/ptp_qoriq.c b/drivers/ptp/ptp_qoriq.c index 08f4cf0ad9e3..5b6ea6d590be 100644 --- 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(®s->ctrl_regs->tmr_cnt_h, hi); } +static void tmr_offset_write(struct ptp_qoriq *ptp_qoriq, u64 delta_ns) +{ + struct ptp_qoriq_registers *regs = &ptp_qoriq->regs; + u32 hi = delta_ns >> 32; + u32 lo = delta_ns & 0xffffffff; + + ptp_qoriq->write(®s->ctrl_regs->tmroff_l, lo); + ptp_qoriq->write(®s->ctrl_regs->tmroff_h, hi); } + +static u64 tmr_offset_read(struct ptp_qoriq *ptp_qoriq) { + struct ptp_qoriq_registers *regs = &ptp_qoriq->regs; + u64 ns; + u32 lo, hi; + + lo = ptp_qoriq->read(®s->ctrl_regs->tmroff_l); + hi = ptp_qoriq->read(®s->ctrl_regs->tmroff_h); + ns = ((u64) hi) << 32; + ns |= lo; + return ns; +} + /* 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 +232,12 @@ 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); spin_lock_irqsave(&ptp_qoriq->lock, flags); - now = tmr_cnt_read(ptp_qoriq); - now += delta; - tmr_cnt_write(ptp_qoriq, now); + tmr_offset_write(ptp_qoriq, delta); set_fipers(ptp_qoriq); spin_unlock_irqrestore(&ptp_qoriq->lock, flags); @@ -232,7 +254,7 @@ 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); @@ -251,6 +273,8 @@ int ptp_qoriq_settime(struct ptp_clock_info *ptp,
ns = timespec64_to_ns(ts);
+ tmr_offset_write(ptp_qoriq, 0); + spin_lock_irqsave(&ptp_qoriq->lock, flags);
tmr_cnt_write(ptp_qoriq, ns); -- 2.17.1
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