[Skiboot] [PATCH 09/10] phb4: Add phb4_check_reg() to sanity check failures

[Michael Neuling]

This adds a function phb4_check_reg() to sanity check when we do MMIO
reads from the PHB to make sure it's not fenced.

This also adds some uses of this function in common locations where
these may occur on PHB reset and link training.

Signed-off-by: Michael Neuling <mikey at neuling.org>
---
 hw/phb4.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/hw/phb4.c b/hw/phb4.c
index 157074fd24..52b814da6c 100644
--- a/hw/phb4.c
+++ b/hw/phb4.c
@@ -306,6 +306,14 @@ static bool phb4_fenced(struct phb4 *p)
 	return true;
 }
 
+static bool phb4_check_reg(struct phb4 *p, uint64_t reg)
+{
+	if (reg == 0xffffffffffffffffUL)
+		return !phb4_fenced(p);
+	return true;
+}
+
+
 /*
  * Configuration space access
  *
@@ -2208,6 +2216,11 @@ static int64_t phb4_poll_link(struct pci_slot *slot)
 		 * link bit at all
 		 */
 		reg = in_be64(p->regs + PHB_PCIE_DLP_TRAIN_CTL);
+		if (!phb4_check_reg(p, reg)) {
+			PHBERR(p, "PHB fence waiting for electrical link\n");
+			return phb4_retry_state(slot);
+		}
+
 		if (reg & (PHB_PCIE_DLP_INBAND_PRESENCE |
 			   PHB_PCIE_DLP_TL_LINKACT)) {
 			PHBDBG(p, "LINK: Electrical link detected\n");
@@ -2224,6 +2237,10 @@ static int64_t phb4_poll_link(struct pci_slot *slot)
 		return pci_slot_set_sm_timeout(slot, msecs_to_tb(100));
 	case PHB4_SLOT_LINK_WAIT:
 		reg = in_be64(p->regs + PHB_PCIE_DLP_TRAIN_CTL);
+		if (!phb4_check_reg(p, reg)) {
+			PHBERR(p, "LINK: PHB fence waiting for link training\n");
+			return phb4_retry_state(slot);
+		}
 		if (reg & PHB_PCIE_DLP_TL_LINKACT) {
 			PHBDBG(p, "LINK: Link is up\n");
 			if (slot->ops.prepare_link_change)
-- 
2.11.0