hw/phb5: Add support for 'Address-Based Interrupt Trigger' mode

The PHB5 introduces a new Address-Based Interrupt mode which extends
the notification offloading to the ESB pages. When ABT is activated,
the PHB maps the interrupt source number into the interrupt command
address. The PHB triggers the interrupt using directly the IC ESB page
of the interrupt number and does not use the notify page of the IC
anymore.

The PHB interrrupt configuration under ABT is a little different. The
'Interrupt Notify Base Address' register points to the base address of
the IC ESB pages and not to the notify page of the IC anymore as on
P9. The 'Interrupt Notify Base Index' register is unused.

This should improve overall performance. The P10 IC can handle higher
interrupt rates compared to P9 and the PHB latency should be improved
under ABT. Debug is easier as the interrupt number is now exposed on
the PowerBUS.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
[FB: port to phb4.c]
Signed-off-by: Frederic Barrat <fbarrat@linux.ibm.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>

1 files changed, 57 insertions, 6 deletions

diff --git a/hw/phb4.c b/hw/phb4.c
index d2d9f9e..d2fc274 100644
--- a/hw/phb4.c
+++ b/hw/phb4.c
@@ -159,6 +159,18 @@ static inline bool phb_pq_disable(struct phb4 *p __unused)
 	return false;
 }
 
+/*
+ * Use the ESB page of the XIVE IC for event notification. Latency
+ * improvement.
+ */
+static inline bool phb_abt_mode(struct phb4 *p __unused)
+{
+	if (is_phb5())
+		return 1;
+
+	return false;
+}
+
 static inline bool phb_can_store_eoi(struct phb4 *p)
 {
 	if (is_phb5())
@@ -5000,12 +5012,49 @@ static const struct phb_ops phb4_ops = {
 
 static void phb4_init_ioda3(struct phb4 *p)
 {
-	/* Init_18 - Interrupt Notify Base Address */
-	out_be64(p->regs + PHB_INT_NOTIFY_ADDR, p->irq_port);
+	if (is_phb5()) {
+		/*
+		 * When ABT is on, the MSIs on the PHB use the PQ state bits
+		 * of the IC and MSI triggers from the PHB are forwarded
+		 * directly to the IC ESB page. However, the LSIs are still
+		 * controlled locally on the PHB and LSI triggers use a
+		 * special offset for trigger injection.
+		 */
+		if (phb_abt_mode(p)) {
+			uint64_t mmio_base = xive2_get_esb_base(p->base_msi);
+
+			PHBDBG(p, "Using ABT mode. ESB: 0x%016llx\n", mmio_base);
+
+			/* Init_18 - Interrupt Notify Base Address */
+			out_be64(p->regs + PHB_INT_NOTIFY_ADDR,
+				 PHB_INT_NOTIFY_ADDR_64K | mmio_base);
+
+			/* Interrupt Notify Base Index is unused */
+		} else {
+			p->irq_port = xive2_get_notify_port(p->chip_id,
+						XIVE_HW_SRC_PHBn(p->index));
+
+			PHBDBG(p, "Using IC notif page at 0x%016llx\n",
+						p->irq_port);
 
-	/* Init_19 - Interrupt Notify Base Index */
-	out_be64(p->regs + PHB_INT_NOTIFY_INDEX,
-		 xive2_get_notify_base(p->base_msi));
+			/* Init_18 - Interrupt Notify Base Address */
+			out_be64(p->regs + PHB_INT_NOTIFY_ADDR, p->irq_port);
+
+			/* Init_19 - Interrupt Notify Base Index */
+			out_be64(p->regs + PHB_INT_NOTIFY_INDEX,
+				 xive2_get_notify_base(p->base_msi));
+		}
+
+	} else { /* p9 */
+		p->irq_port = xive_get_notify_port(p->chip_id,
+						   XIVE_HW_SRC_PHBn(p->index));
+		/* Init_18 - Interrupt Notify Base Address */
+		out_be64(p->regs + PHB_INT_NOTIFY_ADDR, p->irq_port);
+
+		/* Init_19 - Interrupt Notify Base Index */
+		out_be64(p->regs + PHB_INT_NOTIFY_INDEX,
+			 xive_get_notify_base(p->base_msi));
+	}
 
 	/* Init_19x - Not in spec: Initialize source ID */
 	PHBDBG(p, "Reset state SRC_ID: %016llx\n",
@@ -5384,6 +5433,8 @@ static void phb4_init_hw(struct phb4 *p)
 	val |= SETFIELD(PHB_CTRLR_TVT_ADDR_SEL, 0ull, TVT_2_PER_PE);
 	if (phb_pq_disable(p))
 		val |= PHB_CTRLR_IRQ_PQ_DISABLE;
+	if (phb_abt_mode(p))
+		val |= PHB_CTRLR_IRQ_ABT_MODE;
 	if (phb_can_store_eoi(p)) {
 		val |= PHB_CTRLR_IRQ_STORE_EOI;
 		PHBDBG(p, "store EOI is enabled\n");
@@ -5958,7 +6009,7 @@ static void phb4_create(struct dt_node *np)
 		 * ESB pages of the XIVE IC for the MSI sources instead of the
 		 * ESB pages of the PHB.
 		 */
-		if (phb_pq_disable(p)) {
+		if (phb_pq_disable(p) || phb_abt_mode(p)) {
 			xive2_register_esb_source(p->base_msi, p->num_irqs - 8);
 		} else {
 			xive2_register_hw_source(p->base_msi,