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Message-ID: <20121127224605.GA10228@electric-eye.fr.zoreil.com>
Date: Tue, 27 Nov 2012 23:46:05 +0100
From: Francois Romieu <romieu@...zoreil.com>
To: David Laight <David.Laight@...LAB.COM>
Cc: Stéphane ANCELOT <sancelot@...e.fr>,
netdev@...r.kernel.org, sancelot@...alliance.com,
Hayes Wang <hayeswang@...ltek.com>
Subject: Re: Re: RTL 8169 linux driver question
David Laight <David.Laight@...LAB.COM> :
> Stéphane ANCELOT <sancelot@...e.fr> :
> > I had problem with it, my application sends a frame that is immediately
> > transmitted back by some slaves, there was abnormally 100us lost
> > between the send and receive call.
> >
> > Finally I found it was coming from the following register setup in the
> > driver :
> >
> > RTL_W16(IntrMitigate, 0x5151);
> >
> > Can you give me some details about it, since I do not have the RTL8169
> > programming guide.
>
> That sounds like an 'interrupt mitigation' setting - which will cause
> RX interrupts to be delayed a short time in order to reduce the
> interrupt load on the kernel.
>
> There is usually an 'ethtool' setting to disable interrupt mitigation.
Something like the patch below against net-next could help once I will
have tested it.
I completely guessed the Tx usec scale factor at gigabit speed (125 us,
100 us, disabled, who knows ?) and I have no idea which specific chipsets
it should work with.
Hayes, may I expect some hindsight regarding:
1 - the availability of the IntrMitigate (0xe2) register through the
8169, 8168 and 810x line of chipsets
2 - the Tx timer unit at gigabit speed
It would save me some time.
diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
index 248f883..2623b73 100644
--- a/drivers/net/ethernet/realtek/r8169.c
+++ b/drivers/net/ethernet/realtek/r8169.c
@@ -349,6 +349,12 @@ enum rtl_registers {
RxMaxSize = 0xda,
CPlusCmd = 0xe0,
IntrMitigate = 0xe2,
+
+#define RTL_COALESCE_MASK 0x0f
+#define RTL_COALESCE_SHIFT 4
+#define RTL_COALESCE_T_MAX (RTL_COALESCE_MASK)
+#define RTL_COALESCE_FRAME_MAX (RTL_COALESCE_MASK << 2)
+
RxDescAddrLow = 0xe4,
RxDescAddrHigh = 0xe8,
EarlyTxThres = 0xec, /* 8169. Unit of 32 bytes. */
@@ -1997,10 +2003,121 @@ static void rtl8169_get_strings(struct net_device *dev, u32 stringset, u8 *data)
}
}
+static struct rtl_coalesce_scale {
+ u32 speed;
+ /* Rx / Tx */
+ u16 usecs[2];
+} rtl_coalesce_info[] = {
+ { .speed = SPEED_10, .usecs = { 8000, 10000 } },
+ { .speed = SPEED_100, .usecs = { 1000, 1000 } },
+ { .speed = SPEED_1000, .usecs = { 125, 125 } }
+};
+
+static struct rtl_coalesce_scale *rtl_coalesce_scale(struct net_device *dev)
+{
+ struct ethtool_cmd ecmd;
+ int rc, i;
+
+ rc = rtl8169_get_settings(dev, &ecmd);
+ if (rc < 0)
+ return ERR_PTR(rc);
+
+ for (i = 0; i < ARRAY_SIZE(rtl_coalesce_info); i++) {
+ if (ethtool_cmd_speed(&ecmd) == rtl_coalesce_info[i].speed)
+ return rtl_coalesce_info + i;
+ }
+
+ return ERR_PTR(-EINVAL);
+}
+
+static int rtl_get_coalesce(struct net_device *dev, struct ethtool_coalesce *ec)
+{
+ struct rtl8169_private *tp = netdev_priv(dev);
+ void __iomem *ioaddr = tp->mmio_addr;
+ struct rtl_coalesce_scale *scale;
+ struct {
+ u32 *max_frames;
+ u32 *usecs;
+ } coal_settings [] = {
+ { &ec->rx_max_coalesced_frames, &ec->rx_coalesce_usecs },
+ { &ec->tx_max_coalesced_frames, &ec->tx_coalesce_usecs }
+ }, *p = coal_settings;
+ int i;
+ u16 w;
+
+ memset(ec, 0, sizeof(*ec));
+
+ for (w = RTL_R16(IntrMitigate); w; w >>= RTL_COALESCE_SHIFT, p++) {
+ *p->max_frames = (w & RTL_COALESCE_MASK) << 2;
+ w >>= RTL_COALESCE_SHIFT;
+ *p->usecs = w & RTL_COALESCE_MASK;
+ }
+
+ /* Except for null parameeters, the meaning of coalescing parameters
+ * depends on the link speed.
+ */
+ scale = rtl_coalesce_scale(dev);
+ if (PTR_ERR(scale) && (p != coal_settings))
+ return PTR_ERR(scale);
+
+ for (i = 0; i < 2; i++) {
+ p = coal_settings + i;
+ *p->usecs *= scale->usecs[i];
+ if (!*p->usecs && !*p->max_frames)
+ *p->max_frames = 1;
+ }
+
+ return 0;
+}
+
+static int rtl_set_coalesce(struct net_device *dev, struct ethtool_coalesce *ec)
+{
+ struct rtl8169_private *tp = netdev_priv(dev);
+ void __iomem *ioaddr = tp->mmio_addr;
+ struct rtl_coalesce_scale *scale;
+ struct {
+ u32 frames;
+ u32 usecs;
+ } coal_settings [] = {
+ { ec->rx_max_coalesced_frames, ec->rx_coalesce_usecs },
+ { ec->tx_max_coalesced_frames, ec->tx_coalesce_usecs }
+ }, *p = coal_settings;
+ int i, rc;
+ u16 w = 0;
+
+ scale = rtl_coalesce_scale(dev);
+ rc = PTR_ERR(scale);
+
+ for (i = 0; i < 2; i++) {
+ u32 units;
+
+ if (!p->usecs && p->frames == 1)
+ continue;
+ if (rc < 0)
+ goto out;
+
+ units = p->usecs / scale->usecs[i];
+ if (units > RTL_COALESCE_T_MAX || p->usecs % scale->usecs[i] ||
+ p->frames > RTL_COALESCE_FRAME_MAX || p->frames % 4)
+ return -EINVAL;
+
+ w <<= RTL_COALESCE_SHIFT;
+ w |= units;
+ w <<= RTL_COALESCE_SHIFT;
+ w |= p->frames >> 2;
+ }
+
+ RTL_W16(IntrMitigate, swab16(w));
+out:
+ return rc;
+}
+
static const struct ethtool_ops rtl8169_ethtool_ops = {
.get_drvinfo = rtl8169_get_drvinfo,
.get_regs_len = rtl8169_get_regs_len,
.get_link = ethtool_op_get_link,
+ .get_coalesce = rtl_get_coalesce,
+ .set_coalesce = rtl_set_coalesce,
.get_settings = rtl8169_get_settings,
.set_settings = rtl8169_set_settings,
.get_msglevel = rtl8169_get_msglevel,
--
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