[Skiboot] [PATCH v2] phb4/capp: Calculate STQ/DMA read engines based on link-width for PEC

[Vaibhav Jain]

Presently in CAPI mode the number of STQ/DMA-read engines allocated on
PEC2 for CAPP is fixed to 6 and 0-30 respectively irrespective of the
PCI link width. These values are only suitable for x8 cards and
quickly run out if a x16 card is plugged to a PEC2 attached slot. This
usually manifests as CAPP reporting TLBI timeout due to these messages
getting stalled due to insufficient STQs.

To fix this we update enable_capi_mode() to check if PEC2 chiplet is
in x16 mode and if yes then we allocate 4/0-47 STQ/DMA-read engines
for the CAPP traffic.

Cc: stable # v5.7+
Fixes: 37ea3cfdc852("capi: Enable capi mode for PHB4")
Reviewed-by: Andrew Donnellan <andrew.donnellan at au1.ibm.com>
Signed-off-by: Vaibhav Jain <vaibhav at linux.ibm.com>
---
Change-log:
v2 ->	Updated code comment to mention DMA read machines
   	enabled. [Andrew]
	Marked the patch for stable inclusion [Andrew]
---
 hw/phb4.c           | 36 +++++++++++++++++++++++++++---------
 include/phb4-regs.h |  6 ++++++
 2 files changed, 33 insertions(+), 9 deletions(-)

diff --git a/hw/phb4.c b/hw/phb4.c
index ae584d67..2dfcb8dd 100644
--- a/hw/phb4.c
+++ b/hw/phb4.c
@@ -3918,8 +3918,6 @@ static int64_t enable_capi_mode(struct phb4 *p, uint64_t pe_number,
 		return OPAL_HARDWARE;
 	}
 
-	/* CAPP Control Register. Enable CAPP Mode */
-	reg = 0x8000000000000000ULL; /* PEC works in CAPP Mode */
 	if (p->index == CAPP0_PHB_INDEX) {
 		/* PBCQ is operating as a x16 stack
 		 * - The maximum number of engines give to CAPP will be
@@ -3929,17 +3927,37 @@ static int64_t enable_capi_mode(struct phb4 *p, uint64_t pe_number,
 		stq_eng = 0x000E000000000000ULL; /* 14 CAPP msg engines */
 		dma_eng = 0x0000FFFFFFFFFFFFULL; /* 48 CAPP Read machines */
 	}
+
 	if (p->index == CAPP1_PHB_INDEX) {
-		/* PBCQ is operating as a x8 stack
-		 * - The maximum number of engines given to CAPP should
-		 * be 6 and will be assigned in the order of 7 to 2.
-		 * - 0-30 (Read machines) are available for capp use.
-		 */
-		stq_eng = 0x0006000000000000ULL; /* 6 CAPP msg engines */
-		dma_eng = 0x0000FFFFF00E0000ULL; /* 30 Read machines for CAPP Minus 20-27 for DMA */
+		/* Check if PEC is in x8 or x16 mode */
+		xscom_read(p->chip_id, XPEC_PCI2_CPLT_CONF1, &reg);
+
+		if ((reg & XPEC_PCI2_IOVALID_MASK) == XPEC_PCI2_IOVALID_X16) {
+			/* PBCQ is operating as a x16 stack
+			 * - The maximum number of engines give to CAPP will be
+			 * 14 and will be assigned in the order of STQ 15 to 2.
+			 * - 0-47 (Read machines) are available for capp use.
+			 */
+			stq_eng = 0x000E000000000000ULL;
+			dma_eng = 0x0000FFFFFFFFFFFFULL;
+		} else {
+
+			/* PBCQ is operating as a x8 stack
+			 * - The maximum number of engines given to CAPP should
+			 * be 6 and will be assigned in the order of 7 to 2.
+			 * - 0-30 (Read machines) are available for capp use.
+			 */
+			stq_eng = 0x0006000000000000ULL;
+			/* 30 Read machines for CAPP Minus 20-27 for DMA */
+			dma_eng = 0x0000FFFFF00E0000ULL;
+		}
 	}
+
 	if (capp_eng & CAPP_MIN_STQ_ENGINES)
 		stq_eng = 0x0002000000000000ULL; /* 2 capp msg engines */
+
+	/* CAPP Control Register. Enable CAPP Mode */
+	reg = 0x8000000000000000ULL; /* PEC works in CAPP Mode */
 	reg |= stq_eng;
 	if (capp_eng & CAPP_MAX_DMA_READ_ENGINES)
 		dma_eng = 0x0000FF0000000000ULL; /* 16 CAPP Read machines */
diff --git a/include/phb4-regs.h b/include/phb4-regs.h
index 3f87ddcd..e7a190ee 100644
--- a/include/phb4-regs.h
+++ b/include/phb4-regs.h
@@ -400,6 +400,12 @@
 #define   XETU_HV_IND_ADDR_AUTOINC		PPC_BIT(2)
 #define XETU_HV_IND_DATA			0x1
 
+
+/* PCI Chiplet Config Register */
+#define XPEC_PCI2_CPLT_CONF1			0x000000000F000009ULL
+#define XPEC_PCI2_IOVALID_MASK			PPC_BITMASK(4, 6)
+#define XPEC_PCI2_IOVALID_X16			PPC_BIT(4)
+
 /*
  * IODA3 on-chip tables
  */
-- 
2.17.1