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Date: Thu, 24 Jul 2008 16:05:52 -0700
From: Stephen Hemminger <shemminger@...tta.com>
To: Octavian Purdila <opurdila@...acom.com>
Cc: David Miller <davem@...emloft.net>, herbert@...dor.apana.org.au,
netdev@...r.kernel.org
Subject: Re: [RFC][PATCH 1/3] net: per skb control messages
On Fri, 25 Jul 2008 01:35:52 +0300
Octavian Purdila <opurdila@...acom.com> wrote:
> On Friday 25 July 2008, Stephen Hemminger wrote:
>
> > How hard would it be to add PLL support to use same kind of timestamp.
> > Enlist the help of some NTP/clock experts to help.
>
> Let me see if I got this correctly: modify the hardware so that the CPU is
> synchronized with the NIC timestamping unit. If so, I will agree that this is
> the cleanest possible solution.
>
> Thanks,
> tavi
Perodically, sample the hardware clock and the system time of day,
and resynchronize the clocks. I did something like this in a prototype
that never got integrated...
------------------------
Subject: sky2: hardware receive timestamp counter
Use hardware timestamp counter to stamp receive packets.
It allows for higher resolution values without the hardware overhead
of doing gettimeofday.
Signed-off-by: Stephen Hemminger <shemminger@...ux-foundation.org>
---
drivers/net/sky2.c | 159 +++++++++++++++++++++++++++++++++++++++--------------
drivers/net/sky2.h | 5 +
2 files changed, 124 insertions(+), 40 deletions(-)
--- a/drivers/net/sky2.c 2007-08-29 11:41:16.000000000 -0700
+++ b/drivers/net/sky2.c 2007-08-30 13:05:39.000000000 -0700
@@ -26,6 +26,7 @@
#include <linux/kernel.h>
#include <linux/version.h>
#include <linux/module.h>
+#include <linux/reciprocal_div.h>
#include <linux/netdevice.h>
#include <linux/dma-mapping.h>
#include <linux/etherdevice.h>
@@ -2186,6 +2187,36 @@ error:
goto resubmit;
}
+static inline u32 sky2_tist2ns(const struct sky2_hw *hw, u32 clk)
+{
+ return reciprocal_divide(clk * 1000, hw->tist_rate);
+}
+
+/*
+ * Convert hardware timestamp clock into a real time value
+ */
+static void sky2_set_timestamp(struct sk_buff *skb,
+ const struct sky2_hw *hw, u32 stamp)
+{
+ unsigned long seq;
+
+ do {
+ s32 delta;
+
+ seq = read_seqbegin(&hw->tist_lock);
+
+ /* ticks since last synchronization */
+ delta = stamp - hw->tist_base;
+
+ if (delta > 0)
+ skb->tstamp = ktime_add_ns(hw->tist_real,
+ sky2_tist2ns(hw, delta));
+ else
+ skb->tstamp = ktime_sub_ns(hw->tist_real,
+ sky2_tist2ns(hw, -delta));
+ } while (read_seqretry(&hw->tist_lock, seq));
+}
+
/* Transmit complete */
static inline void sky2_tx_done(struct net_device *dev, u16 last)
{
@@ -2262,6 +2293,16 @@ static int sky2_status_intr(struct sky2_
break;
#ifdef SKY2_VLAN_TAG_USED
+ case OP_RXTIMEVLAN:
+ sky2->rx_tag = length;
+ /* fall through */
+#endif
+ case OP_RXTIMESTAMP:
+ skb = sky2->rx_ring[sky2->rx_next].skb;
+ sky2_set_timestamp(skb, hw, status);
+ break;
+
+#ifdef SKY2_VLAN_TAG_USED
case OP_RXVLAN:
sky2->rx_tag = length;
break;
@@ -2375,9 +2416,6 @@ static void sky2_hw_intr(struct sky2_hw
{
struct pci_dev *pdev = hw->pdev;
u32 status = sky2_read32(hw, B0_HWE_ISRC);
- u32 hwmsk = sky2_read32(hw, B0_HWE_IMSK);
-
- status &= hwmsk;
if (status & Y2_IS_TIST_OV)
sky2_write8(hw, GMAC_TI_ST_CTRL, GMT_ST_CLR_IRQ);
@@ -2457,11 +2495,15 @@ static void sky2_le_error(struct sky2_hw
sky2_write32(hw, Q_ADDR(q, Q_CSR), BMU_CLR_IRQ_CHK);
}
-/* Check for lost IRQ once a second */
+/* Once a second timer for safety checking and polling for timestamp
+ *
+ * Note: receive and timer processing both happen under softirq
+ */
static void sky2_watchdog(unsigned long arg)
{
struct sky2_hw *hw = (struct sky2_hw *) arg;
+ /* Look for lost IRQ */
if (sky2_read32(hw, B0_ISRC)) {
struct net_device *dev = hw->dev[0];
@@ -2469,6 +2511,14 @@ static void sky2_watchdog(unsigned long
__netif_rx_schedule(dev);
}
+ /* Snapshot current system realtime at current timestamp value
+ * @ 150Mhz counter wraps in 28.6 secs
+ */
+ write_seqlock(&hw->tist_lock);
+ hw->tist_real = ktime_get_real();
+ hw->tist_base = sky2_read32(hw, GMAC_TI_ST_VAL);
+ write_sequnlock(&hw->tist_lock);
+
if (hw->active > 0)
mod_timer(&hw->watchdog_timer, round_jiffies(jiffies + HZ));
}
@@ -2476,9 +2526,6 @@ static void sky2_watchdog(unsigned long
/* Hardware/software error handling */
static void sky2_err_intr(struct sky2_hw *hw, u32 status)
{
- if (net_ratelimit())
- dev_warn(&hw->pdev->dev, "error interrupt status=%#x\n", status);
-
if (status & Y2_IS_HW_ERR)
sky2_hw_intr(hw);
@@ -2707,9 +2754,9 @@ static void sky2_reset(struct sky2_hw *h
/* Turn off descriptor polling */
sky2_write32(hw, B28_DPT_CTRL, DPT_STOP);
- /* Turn off receive timestamp */
- sky2_write8(hw, GMAC_TI_ST_CTRL, GMT_ST_STOP);
- sky2_write8(hw, GMAC_TI_ST_CTRL, GMT_ST_CLR_IRQ);
+ /* Turn on receive timestamp */
+ sky2_write32(hw, GMAC_TI_ST_VAL, 0);
+ sky2_write8(hw, GMAC_TI_ST_CTRL, GMT_ST_CLR_IRQ|GMT_ST_START);
/* enable the Tx Arbiters */
for (i = 0; i < hw->ports; i++)
@@ -4061,6 +4108,9 @@ static int __devinit sky2_probe(struct p
sky2_show_addr(dev1);
}
+ seqlock_init(&hw->tist_lock);
+ hw->tist_rate = reciprocal_value(sky2_mhz(hw));
+
setup_timer(&hw->watchdog_timer, sky2_watchdog, (unsigned long) hw);
INIT_WORK(&hw->restart_work, sky2_restart);
--- a/drivers/net/sky2.h 2007-08-29 11:41:16.000000000 -0700
+++ b/drivers/net/sky2.h 2007-08-30 13:01:50.000000000 -0700
@@ -352,7 +352,7 @@ enum {
/* Hardware error interrupt mask for Yukon 2 */
enum {
- Y2_IS_TIST_OV = 1<<29,/* Time Stamp Timer overflow interrupt */
+ Y2_IS_TIST_OV = 1<<29, /* Time Stamp Timer overflow interrupt */
Y2_IS_SENSOR = 1<<28, /* Sensor interrupt */
Y2_IS_MST_ERR = 1<<27, /* Master error interrupt */
Y2_IS_IRQ_STAT = 1<<26, /* Status exception interrupt */
@@ -2032,6 +2032,11 @@ struct sky2_hw {
u8 ports;
u8 active;
+ seqlock_t tist_lock;
+ ktime_t tist_real;
+ u32 tist_base;
+ u32 tist_rate;
+
struct sky2_status_le *st_le;
u32 st_idx;
dma_addr_t st_dma;
--
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