[Skiboot] [PATCH skiboot] hw/phb3/naples: Disable D-states

[Alexey Kardashevskiy]

Putting "Mellanox Technologies MT27700 Family [ConnectX-4] [15b3:1013]"
(more precisely, the second of 2 its PCI functions, no matter in what
order) into the D3 state causes EEH with the "PCT timeout" error.
This has been noticed on garrison machines only and firestones do not
seem to have this issue.

This disables D-states changing for devices on root buses on Naples by
installing a config space access filter (copied from PHB4).

Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
---
 hw/phb3.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/hw/phb3.c b/hw/phb3.c
index 771ccfc..04c8b78 100644
--- a/hw/phb3.c
+++ b/hw/phb3.c
@@ -573,6 +573,22 @@ static void phb3_endpoint_init(struct phb *phb,
 	pci_cfg_write32(phb, bdfn, aercap + PCIECAP_AER_CAPCTL, val32);
 }
 
+static int64_t phb3_pcicfg_no_dstate(void *dev __unused,
+				     struct pci_cfg_reg_filter *pcrf,
+				     uint32_t offset, uint32_t len __unused,
+				     uint32_t *data __unused,  bool write)
+{
+	uint32_t loff = offset - pcrf->start;
+
+	/* Disable D-state change on children of the PHB. For now we
+	 * simply block all writes to the PM control/status
+	 */
+	if (write && loff >= 4 && loff < 6)
+		return OPAL_SUCCESS;
+
+	return OPAL_PARTIAL;
+}
+
 static void phb3_check_device_quirks(struct phb *phb, struct pci_device *dev)
 {
 	struct phb3 *p = phb_to_phb3(phb);
@@ -601,6 +617,19 @@ static void phb3_check_device_quirks(struct phb *phb, struct pci_device *dev)
 		else
 			modectl &= ~PPC_BIT(14);
 		xscom_write(p->chip_id, p->pe_xscom + 0x0b, modectl);
+
+		/*
+		 * Naples has a problem with D-states at least on Mellanox CX4,
+		 * disable changing D-state on Naples like we do it for PHB4.
+		 */
+		if (PHB3_IS_NAPLES(p) &&
+		    pci_has_cap(dev, PCI_CFG_CAP_ID_PM, false)) {
+			pci_add_cfg_reg_filter(dev,
+					pci_cap(dev, PCI_CFG_CAP_ID_PM, false),
+					8,
+					PCI_REG_FLAG_WRITE,
+					phb3_pcicfg_no_dstate);
+		}
 	} else if (dev->primary_bus == 0) {
 		/*
 		 * Emulate the prefetchable window of the root port
-- 
2.17.1