Add facilities for tuning the "em" driver's interrupt delays without

recompiling the driver.  See the comments near the top of "if_em.h"
for descriptions of these delays.  Four new loader tunables control
the system-wide default values:

    hw.em.tx_int_delay
    hw.em.rx_int_delay
    hw.em.tx_abs_int_delay
    hw.em.rx_abs_int_delay

The tunables are specified in microseconds.  The valid range is
0-67108 usec., and 0 means that the timer is disabled.

There are also four new sysctls (actually, a set of four for each
"em" device in the system) to query and change the interrupt delays
after the system is up:

    hw.em0.tx_int_delay
    hw.em0.rx_int_delay
    hw.em0.tx_abs_int_delay (not present for 82542/3/4 adapters)
    hw.em0.rx_abs_int_delay (not present for 82542/3/4 adapters)

It seems to be OK to change these values even while the adapter is
passing traffic.

Approved by:	Prafulla Deuskar <pdeuskar@FreeBSD.ORG>
MFC after:	4 weeks

1 files changed, 11 insertions, 4 deletions

diff --git a/sys/dev/em/if_em.h b/sys/dev/em/if_em.h
index 2532740..ca85fbb 100644
--- a/sys/dev/em/if_em.h
+++ b/sys/dev/em/if_em.h
@@ -294,6 +294,13 @@ typedef enum _XSUM_CONTEXT_T {
 	OFFLOAD_UDP_IP
 } XSUM_CONTEXT_T;
 
+struct adapter;
+struct em_int_delay_info {
+	struct adapter *adapter;	/* Back-pointer to the adapter struct */
+	int offset;			/* Register offset to read/write */
+	int value;			/* Current value in usecs */
+};
+
 /* Our adapter structure */
 struct adapter {
 	struct arpcom   interface_data;
@@ -320,10 +327,10 @@ struct adapter {
 	u_int16_t       link_speed;
 	u_int16_t       link_duplex;
 	u_int32_t       smartspeed;
-	u_int32_t       tx_int_delay;
-	u_int32_t       tx_abs_int_delay;
-	u_int32_t       rx_int_delay;
-	u_int32_t       rx_abs_int_delay;
+	struct em_int_delay_info tx_int_delay;
+	struct em_int_delay_info tx_abs_int_delay;
+	struct em_int_delay_info rx_int_delay;
+	struct em_int_delay_info rx_abs_int_delay;
 
 	XSUM_CONTEXT_T  active_checksum_context;