Device Polling code for -current.

Non-SMP, i386-only, no polling in the idle loop at the moment.

To use this code you must compile a kernel with

        options DEVICE_POLLING

and at runtime enable polling with

        sysctl kern.polling.enable=1

The percentage of CPU reserved to userland can be set with

        sysctl kern.polling.user_frac=NN (default is 50)

while the remainder is used by polling device drivers and netisr's.
These are the only two variables that you should need to touch. There
are a few more parameters in kern.polling but the default values
are adequate for all purposes. See the code in kern_poll.c for
more details on them.

Polling in the idle loop will be implemented shortly by introducing
a kernel thread which does the job. Until then, the amount of CPU
dedicated to polling will never exceed (100-user_frac).
The equivalent (actually, better) code for -stable is at

	http://info.iet.unipi.it/~luigi/polling/

and also supports polling in the idle loop.

NOTE to Alpha developers:
There is really nothing in this code that is i386-specific.
If you move the 2 lines supporting the new option from
sys/conf/{files,options}.i386 to sys/conf/{files,options} I am
pretty sure that this should work on the Alpha as well, just that
I do not have a suitable test box to try it. If someone feels like
trying it, I would appreciate it.

NOTE to other developers:
sure some things could be done better, and as always I am open to
constructive criticism, which a few of you have already given and
I greatly appreciated.
However, before proposing radical architectural changes, please
take some time to possibly try out this code, or at the very least
read the comments in kern_poll.c, especially re. the reason why I
am using a soft netisr and cannot (I believe) replace it with a
simple timeout.

Quick description of files touched by this commit:

sys/conf/files.i386
        new file kern/kern_poll.c
sys/conf/options.i386
        new option
sys/i386/i386/trap.c
        poll in trap (disabled by default)
sys/kern/kern_clock.c
        initialization and hardclock hooks.
sys/kern/kern_intr.c
        minor swi_net changes
sys/kern/kern_poll.c
        the bulk of the code.
sys/net/if.h
        new flag
sys/net/if_var.h
        declaration for functions used in device drivers.
sys/net/netisr.h
        NETISR_POLL
sys/dev/fxp/if_fxp.c
sys/dev/fxp/if_fxpvar.h
sys/pci/if_dc.c
sys/pci/if_dcreg.h
sys/pci/if_sis.c
sys/pci/if_sisreg.h
        device driver modifications

2 files changed, 63 insertions, 2 deletions

diff --git a/sys/dev/fxp/if_fxp.c b/sys/dev/fxp/if_fxp.c
index 840ed87..27b7843 100644
--- a/sys/dev/fxp/if_fxp.c
+++ b/sys/dev/fxp/if_fxp.c
@@ -1141,6 +1141,38 @@ tbdinit:
 	}
 }
 
+static void fxp_intr_body(struct fxp_softc *sc, u_int8_t statack, int count);
+
+#ifdef DEVICE_POLLING
+static poll_handler_t fxp_poll;
+
+static void
+fxp_poll(struct ifnet *ifp, enum poll_cmd cmd, int count)  
+{
+	struct fxp_softc *sc = ifp->if_softc;
+	u_int8_t statack ;
+
+	if (cmd == POLL_DEREGISTER) {	/* final call, enable interrupts */
+		CSR_WRITE_1(sc, FXP_CSR_SCB_INTRCNTL, 0);
+		return;
+	}
+	statack = FXP_SCB_STATACK_CXTNO | FXP_SCB_STATACK_CNA |
+		FXP_SCB_STATACK_FR ;
+	if (cmd == POLL_AND_CHECK_STATUS) {
+		u_int8_t tmp ;
+		tmp = CSR_READ_1(sc, FXP_CSR_SCB_STATACK);
+		if (tmp == 0xff || tmp == 0)
+			return ; /* nothing to do */
+		tmp &= ~statack ;
+		/* ack what we can */
+		if (tmp != 0)
+			CSR_WRITE_1(sc, FXP_CSR_SCB_STATACK, tmp);
+		statack |= tmp ;
+	}
+	fxp_intr_body(sc, statack, count);
+}
+#endif /* DEVICE_POLLING */
+
 /*
  * Process interface interrupts.
  */
@@ -1148,9 +1180,21 @@ static void
 fxp_intr(void *xsc)
 {
 	struct fxp_softc *sc = xsc;
-	struct ifnet *ifp = &sc->sc_if;
 	u_int8_t statack;
 
+#ifdef DEVICE_POLLING
+	struct ifnet *ifp = &sc->sc_if;
+
+	if (ifp->if_ipending & IFF_POLLING)
+		return ;
+	if (ether_poll_register(fxp_poll, ifp)) {
+		/* disable interrupts */
+		CSR_WRITE_1(sc, FXP_CSR_SCB_INTRCNTL, FXP_SCB_INTR_DISABLE);
+		fxp_poll(ifp, 0, 1);
+		return ;
+	}
+#endif
+
 	if (sc->suspended) {
 		return;
 	}
@@ -1169,6 +1213,14 @@ fxp_intr(void *xsc)
 		 * First ACK all the interrupts in this pass.
 		 */
 		CSR_WRITE_1(sc, FXP_CSR_SCB_STATACK, statack);
+		fxp_intr_body(sc, statack, -1);
+	}
+}
+
+static void
+fxp_intr_body(struct fxp_softc *sc, u_int8_t statack, int count)
+{
+	struct ifnet *ifp = &sc->sc_if;
 
 		/*
 		 * Free any finished transmit mbuf chains.
@@ -1220,6 +1272,9 @@ rcvloop:
 			rfa = (struct fxp_rfa *)(m->m_ext.ext_buf +
 			    RFA_ALIGNMENT_FUDGE);
 
+#ifdef DEVICE_POLLING /* loop at most count times if count >=0 */
+			if (count < 0 || count-- > 0)
+#endif
 			if (rfa->rfa_status & FXP_RFA_STATUS_C) {
 				/*
 				 * Remove first packet from the chain.
@@ -1276,7 +1331,6 @@ rcvloop:
 				fxp_scb_cmd(sc, FXP_SCB_COMMAND_RU_START);
 			}
 		}
-	}
 }
 
 /*
@@ -1404,6 +1458,9 @@ fxp_stop(struct fxp_softc *sc)
 	ifp->if_flags &= ~(IFF_RUNNING | IFF_OACTIVE);
 	ifp->if_timer = 0;
 
+#ifdef DEVICE_POLLING
+	ether_poll_deregister(ifp);
+#endif
 	/*
 	 * Cancel stats updater.
 	 */
diff --git a/sys/dev/fxp/if_fxpvar.h b/sys/dev/fxp/if_fxpvar.h
index 23fdaa4..b2ae9b2 100644
--- a/sys/dev/fxp/if_fxpvar.h
+++ b/sys/dev/fxp/if_fxpvar.h
@@ -57,7 +57,11 @@
  * Number of receive frame area buffers. These are large so chose
  * wisely.
  */
+#ifdef DEVICE_POLLING
+#define FXP_NRFABUFS	192
+#else
 #define FXP_NRFABUFS    64
+#endif
 
 /*
  * Maximum number of seconds that the receiver can be idle before we