phb4: Block D-state power management on direct slots

As current revisions of PHB4 don't properly handle the resulting
L1 link transition.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

core/pci.c

@@ -202,11 +202,21 @@ static void pci_init_aer_cap(struct phb *phb, struct pci_device *pd)
 		pci_set_cap(pd, PCIECAP_ID_AER, pos, NULL, true);
 }
 
+static void pci_init_pm_cap(struct phb *phb, struct pci_device *pd)
+{
+	int64_t pos;
+
+	pos = pci_find_cap(phb, pd->bdfn, PCI_CFG_CAP_ID_PM);
+	if (pos > 0)
+		pci_set_cap(pd, PCI_CFG_CAP_ID_PM, pos, NULL, false);
+}
+
 void pci_init_capabilities(struct phb *phb, struct pci_device *pd)
 {
 	pci_init_pcie_cap(phb, pd);
 	pci_init_aer_cap(phb, pd);
 	pci_init_iov_cap(phb, pd);
+	pci_init_pm_cap(phb, pd);
 }
 
 static struct pci_device *pci_scan_one(struct phb *phb, struct pci_device *parent,

hw/phb4.c

@@ -644,19 +644,45 @@ static void phb4_endpoint_init(struct phb *phb,
 	pci_cfg_write32(phb, bdfn, aercap + PCIECAP_AER_CAPCTL, val32);
 }
 
+static int64_t phb4_pcicfg_no_dstate(void *dev,
+				     struct pci_cfg_reg_filter *pcrf,
+				     uint32_t offset, uint32_t len,
+				     uint32_t *data,  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 phb4_check_device_quirks(struct phb *phb, struct pci_device *dev)
 {
-	// FIXME: add quirks later if necessary
+	/* Some special adapter tweaks for devices directly under the PHB */
+	if (dev->primary_bus != 1)
+		return;
+
+	/* PM quirk */
+	if (!pci_has_cap(dev, PCI_CFG_CAP_ID_PM, false))
+		return;
+
+	pci_add_cfg_reg_filter(dev,
+			       pci_cap(dev, PCI_CFG_CAP_ID_PM, false), 8,
+			       PCI_REG_FLAG_WRITE,
+			       phb4_pcicfg_no_dstate);
 }
 
 static int phb4_device_init(struct phb *phb, struct pci_device *dev,
 			    void *data __unused)
 {
 	int ecap, aercap;
 
-	/* Some special adapter tweaks for devices directly under the PHB */
-	if (dev->primary_bus == 1)
-		phb4_check_device_quirks(phb, dev);
+	/* Setup special device quirks */
+	phb4_check_device_quirks(phb, dev);
 
 	/* Common initialization for the device */
 	pci_device_init(phb, dev);

include/pci-cfg.h

@@ -108,6 +108,9 @@
 #define PCI_CFG_CAP_ID			0
 #define PCI_CFG_CAP_NEXT		1
 
+/* PCI Power Management capability */
+#define PCI_CFG_CAP_ID_PM		1
+
 /* PCI bridge subsystem ID capability */
 #define PCI_CFG_CAP_ID_SUBSYS_VID	0x0d
 #define   PCICAP_SUBSYS_VID_VENDOR	4