git: 9bf9164fc8aa - main - e1000: Clean up ITR/EITR in preparation for AIM

The branch main has been updated by kbowling:

URL: https://cgit.FreeBSD.org/src/commit/?id=9bf9164fc8aad1ca828c725413e06462aef1e4dd

commit 9bf9164fc8aad1ca828c725413e06462aef1e4dd
Author:     Kevin Bowling <kbowling@FreeBSD.org>
AuthorDate: 2024-09-27 08:03:31 +0000
Commit:     Kevin Bowling <kbowling@FreeBSD.org>
CommitDate: 2024-09-27 08:30:05 +0000

    e1000: Clean up ITR/EITR in preparation for AIM
    
    Provide macros to derive the various needed values and make it a bit
    more clear the differences between em and igb.
    
    The igb default EITR was not landing at the right offset.
    
    Respect the 'max_interrupt_rate' tunable.
    
    MFC after:      1 week
    Sponsored by:   BBOX.io
---
 sys/dev/e1000/if_em.c | 20 ++++++++------------
 sys/dev/e1000/if_em.h | 11 +++++++++--
 2 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/sys/dev/e1000/if_em.c b/sys/dev/e1000/if_em.c
index cdadec17e355..b9c6131e6741 100644
--- a/sys/dev/e1000/if_em.c
+++ b/sys/dev/e1000/if_em.c
@@ -499,9 +499,6 @@ static driver_t igb_if_driver = {
 #define EM_TICKS_TO_USECS(ticks)	((1024 * (ticks) + 500) / 1000)
 #define EM_USECS_TO_TICKS(usecs)	((1000 * (usecs) + 512) / 1024)
 
-#define MAX_INTS_PER_SEC	8000
-#define DEFAULT_ITR		(1000000000/(MAX_INTS_PER_SEC * 256))
-
 /* Allow common code without TSO */
 #ifndef CSUM_TSO
 #define CSUM_TSO	0
@@ -551,7 +548,7 @@ SYSCTL_INT(_hw_em, OID_AUTO, eee_setting, CTLFLAG_RDTUN, &eee_setting, 0,
 /*
 ** Tuneable Interrupt rate
 */
-static int em_max_interrupt_rate = 8000;
+static int em_max_interrupt_rate = EM_INTS_PER_SEC;
 SYSCTL_INT(_hw_em, OID_AUTO, max_interrupt_rate, CTLFLAG_RDTUN,
     &em_max_interrupt_rate, 0, "Maximum interrupts per second");
 
@@ -1050,7 +1047,8 @@ em_if_attach_pre(if_ctx_t ctx)
 		    E1000_REGISTER(hw, E1000_TADV), em_tx_abs_int_delay_dflt);
 		em_add_int_delay_sysctl(sc, "itr",
 		    "interrupt delay limit in usecs/4", &sc->tx_itr,
-		    E1000_REGISTER(hw, E1000_ITR), DEFAULT_ITR);
+		    E1000_REGISTER(hw, E1000_ITR),
+			EM_INTS_TO_ITR(em_max_interrupt_rate));
 	}
 
 	hw->mac.autoneg = DO_AUTO_NEG;
@@ -2287,7 +2285,7 @@ igb_configure_queues(struct e1000_softc *sc)
 
 	/* Set the igb starting interrupt rate */
 	if (em_max_interrupt_rate > 0) {
-		newitr = (4000000 / em_max_interrupt_rate) & 0x7FFC;
+		newitr = IGB_INTS_TO_EITR(em_max_interrupt_rate);
 
 		if (hw->mac.type == e1000_82575)
 			newitr |= newitr << 16;
@@ -3386,11 +3384,9 @@ em_initialize_receive_unit(if_ctx_t ctx)
 		if (hw->mac.type >= e1000_82540) {
 			E1000_WRITE_REG(hw, E1000_RADV, sc->rx_abs_int_delay.value);
 
-			/*
-			 * Set the interrupt throttling rate. Value is calculated
-			 * as DEFAULT_ITR = 1/(MAX_INTS_PER_SEC * 256ns)
-			 */
-			E1000_WRITE_REG(hw, E1000_ITR, DEFAULT_ITR);
+			/* Set the default interrupt throttling rate */
+			E1000_WRITE_REG(hw, E1000_ITR,
+			    EM_INTS_TO_ITR(em_max_interrupt_rate));
 		}
 
 		/* XXX TEMPORARY WORKAROUND: on some systems with 82573
@@ -3418,7 +3414,7 @@ em_initialize_receive_unit(if_ctx_t ctx)
 		if (hw->mac.type == e1000_82574) {
 			for (int i = 0; i < 4; i++)
 				E1000_WRITE_REG(hw, E1000_EITR_82574(i),
-				    DEFAULT_ITR);
+				    EM_INTS_TO_ITR(em_max_interrupt_rate));
 			/* Disable accelerated acknowledge */
 			rfctl |= E1000_RFCTL_ACK_DIS;
 		}
diff --git a/sys/dev/e1000/if_em.h b/sys/dev/e1000/if_em.h
index 244762e8ed0d..7219dc57c333 100644
--- a/sys/dev/e1000/if_em.h
+++ b/sys/dev/e1000/if_em.h
@@ -244,8 +244,15 @@
 #define IGB_MEDIA_RESET		(1 << 0)
 
 /* Define the starting Interrupt rate per Queue */
-#define IGB_INTS_PER_SEC	8000
-#define IGB_DEFAULT_ITR		((1000000/IGB_INTS_PER_SEC) << 2)
+#define EM_INTS_PER_SEC		8000
+#define EM_INTS_MULTIPLIER	256
+#define EM_ITR_DIVIDEND		1000000000
+#define EM_INTS_TO_ITR(i)	(EM_ITR_DIVIDEND/(i * EM_INTS_MULTIPLIER))
+#define IGB_ITR_DIVIDEND	1000000
+#define IGB_ITR_SHIFT		2
+#define IGB_QVECTOR_MASK	0x7FFC
+#define IGB_INTS_TO_EITR(i)	(((IGB_ITR_DIVIDEND/i) & IGB_QVECTOR_MASK) << \
+				    IGB_ITR_SHIFT)
 
 #define IGB_LINK_ITR		2000
 #define I210_LINK_DELAY		1000