[Skiboot] [PATCH 2/2] phb4: Disable nodal scoped DMA accesses when PB pump mode is enabled

[Alistair Popple]

When pump mode is enabled on the PowerBus each chip is in a different group
rather than a different node so disable nodal broadcasts when pump mode is
enabled. This provides a performance boost on some systems, particularly
those utilising GPU direct with NVLink2.

Signed-off-by: Alistair Popple <alistair at popple.id.au>
---
 hw/phb4.c           | 11 +++++++++++
 include/phb4-regs.h |  2 ++
 2 files changed, 13 insertions(+)

diff --git a/hw/phb4.c b/hw/phb4.c
index 7f188684..8ba3eb78 100644
--- a/hw/phb4.c
+++ b/hw/phb4.c
@@ -3983,6 +3983,17 @@ static int64_t enable_capi_mode(struct phb4 *p, uint64_t pe_number,
 			 XPEC_NEST_PBCQ_HW_CONFIG_PBINIT,
 			 XPEC_NEST_PBCQ_HW_CONFIG_PBINIT);
 
+	/* If pump mode is enabled don't do nodal broadcasts.
+	 */
+	xscom_read(p->chip_id, PB_CENT_HP_MODE_CURR, &reg);
+	if (reg & PB_CFG_PUMP_MODE) {
+		reg = XPEC_NEST_PBCQ_HW_CONFIG_DIS_NODAL;
+		reg |= XPEC_NEST_PBCQ_HW_CONFIG_DIS_RNNN;
+		xscom_write_mask(p->chip_id,
+				 p->pe_xscom + XPEC_NEST_PBCQ_HW_CONFIG,
+				 reg, reg);
+	}
+
 	/* PEC Phase 4 (PHB) registers adjustment
 	 * Inbound CAPP traffic: The CAPI can send both CAPP packets and
 	 * I/O packets. A PCIe packet is indentified as a CAPP packet in
diff --git a/include/phb4-regs.h b/include/phb4-regs.h
index e7a190ee..d7b551f3 100644
--- a/include/phb4-regs.h
+++ b/include/phb4-regs.h
@@ -344,6 +344,8 @@
 #define XPEC_NEST_PBCQ_HW_CONFIG		0x0
 #define   XPEC_NEST_PBCQ_HW_CONFIG_PBINIT	PPC_BIT(12)
 #define   XPEC_NEST_PBCQ_HW_CONFIG_CH_STR	PPC_BIT(33)
+#define   XPEC_NEST_PBCQ_HW_CONFIG_DIS_NODAL	PPC_BIT(50)
+#define   XPEC_NEST_PBCQ_HW_CONFIG_DIS_RNNN	PPC_BIT(52)
 #define XPEC_NEST_CAPP_CNTL			0x7
 
 /* Nest base per-stack registers */
-- 
2.11.0