[Skiboot] [PATCH 6/8] astbmc/p8dnu: Enable PCI slot's power supply on PEX9733 in hot-add path

[Gavin Shan]

This issue is reported from superMicro's "p8dnu" platform. PEX9733
is connected to PHB direct slot. We create dynamic PCI slots for
its (5) downstream ports and all of them support surprise hotplug
capability. The problem is power supply lost on hot-remove and it
isn't turned on automatically on hot-add. It means the PCIe link
behind the slot isn't up and the PCI adapter behind the slot can't
be probed successfully.

This fixes the issue by forcing to turn on the power supply on
hardware when user (kernel) requests to do so. Those PCI slots
are identified by additional flag (PCI_SLOT_FLAG_FORCE_POWERON).

Reported-by: Hank Chang <hankmax0000 at gmail.com>
Signed-off-by: Gavin Shan <gwhsan at linux.vnet.ibm.com>
Tested-by: Willie Liauw <williel at supermicro.com.tw>
---
 core/pcie-slot.c         | 13 ++++++++++---
 include/pci-slot.h       |  1 +
 platforms/astbmc/slots.c | 13 +++++++++++++
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/core/pcie-slot.c b/core/pcie-slot.c
index 72068ba..e92aa8d 100644
--- a/core/pcie-slot.c
+++ b/core/pcie-slot.c
@@ -227,15 +227,22 @@ static int64_t pcie_slot_set_power_state_ext(struct pci_slot *slot, uint8_t val,
 	 * only concerned in surprise hotplug path. In managed hot-add path,
 	 * the PCIe link should have been ready before we power on the slot.
 	 * However, it's not harmful to do so in managed hot-add path.
+	 *
+	 * When flag PCI_SLOT_FLAG_FORCE_POWERON is set for the PCI slot, we
+	 * should turn on the slot's power supply on hardware on user's request
+	 * because that might have been lost. Otherwise, the PCIe link behind
+	 * the slot won't become ready for ever and PCI adapter behind the slot
+	 * can't be probed successfully.
 	 */
 	if (surprise_check && slot->surprise_pluggable) {
 		slot->power_state = val;
-		if (val == PCI_SLOT_POWER_ON) {
+		if (val == PCI_SLOT_POWER_OFF)
+			return OPAL_SUCCESS;
+
+		if (!pci_slot_has_flags(slot, PCI_SLOT_FLAG_FORCE_POWERON)) {
 			pci_slot_set_state(slot, PCI_SLOT_STATE_SPOWER_DONE);
 			return OPAL_ASYNC_COMPLETION;
 		}
-
-		return OPAL_SUCCESS;
 	}
 
 	pci_slot_set_state(slot, PCI_SLOT_STATE_SPOWER_START);
diff --git a/include/pci-slot.h b/include/pci-slot.h
index ce3e8dd..7f16ddd 100644
--- a/include/pci-slot.h
+++ b/include/pci-slot.h
@@ -146,6 +146,7 @@ struct pci_slot_ops {
 struct pci_slot {
 	uint32_t		flags;
 #define PCI_SLOT_FLAG_BOOTUP		0x1
+#define PCI_SLOT_FLAG_FORCE_POWERON	0x2
 
 	struct phb		*phb;
 	struct pci_device	*pd;
diff --git a/platforms/astbmc/slots.c b/platforms/astbmc/slots.c
index aeca007..f28ad7d 100644
--- a/platforms/astbmc/slots.c
+++ b/platforms/astbmc/slots.c
@@ -166,6 +166,19 @@ static void create_dynamic_slot(struct phb *phb, struct pci_device *pd)
 	slot = pcie_slot_create(phb, pd);
 	assert(slot);
 	init_slot_info(slot, true, NULL);
+
+	/* On superMicro's "p8dnu" platform, we create dynamic PCI slots
+	 * for all downstream ports of PEX9733 that is connected to PHB
+	 * direct slot. The power supply to the PCI slot is lost after
+	 * PCI adapter is removed from it. The power supply can't be
+	 * turned on when the slot is in empty state. The power supply
+	 * isn't turned on automatically when inserting PCI adapter to
+	 * the slot at later point. We set a flag to the slot here, to
+	 * turn on the power supply in (suprise or managed) hot-add path.
+	 */
+	if (dt_node_is_compatible(dt_root, "supermicro,p8dnu") &&
+	    slot->pd && slot->pd->vdid == 0x973310b5)
+		pci_slot_add_flags(slot, PCI_SLOT_FLAG_FORCE_POWERON);
 }
 
 void slot_table_get_slot_info(struct phb *phb, struct pci_device *pd)
-- 
2.7.4