[Skiboot] [PATCH] phb4: Reset pfir and nfir if new errors reported during ETU reset

[Vaibhav Jain]

During fast-reboot a PCI device can continue sending requests even
after ETU-Reset is asserted. This will cause new errors to be reported
in ETU fir-registers and will result in values of variables nfir_cache
and pfir_cache to be out of sync.

Presently during step-2 of CRESET nfir_cache and pfir_cache values are
used to bring the PHB out of reset state. However if these variables
are out of date the nfir/pfir registers are never reset completely and
ETU still remains frozen.

Hence this patch updates step-2 of phb4_creset to re-read the values of
nfir/pfir registers to check if any new errors were reported after
ETU-reset was asserted, report these new errors and reset the
nfir/pfir registers. This should bring the ETU out of reset
successfully.

Signed-off-by: Vaibhav Jain <vaibhav at linux.ibm.com>
---
 hw/phb4.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/hw/phb4.c b/hw/phb4.c
index d1245dce..9c4b54b5 100644
--- a/hw/phb4.c
+++ b/hw/phb4.c
@@ -3148,6 +3148,33 @@ static int64_t phb4_creset(struct pci_slot *slot)
 			xscom_write(p->chip_id, p->pe_stk_xscom + 0x1,
 				    ~p->nfir_cache);
 
+			/* Re-read errors in PFIR and NFIR and reset any new
+			 * error reported. This may happen as after fundamental
+			 * reset was asserted in previous step the device may
+			 * still be sending TLPs causing fence to be raised.
+			 */
+			xscom_read(p->chip_id, p->pci_stk_xscom +
+				   XPEC_PCI_STK_PCI_FIR, &p->pfir_cache);
+			xscom_read(p->chip_id, p->pe_stk_xscom +
+				   XPEC_NEST_STK_PCI_NFIR, &p->nfir_cache);
+
+			if (p->pfir_cache || p->nfir_cache) {
+				PHBERR(p, "CRESET: PHB still fenced !!\n");
+				PHBERR(p, "PCI FIR=0x%016llx\n",
+				       p->pfir_cache);
+				PHBERR(p, "NEST FIR=0x%016llx\n",
+				       p->nfir_cache);
+
+				/* Dump other error registers */
+				phb4_eeh_dump_regs(p);
+
+				/* Reset the PHB errors */
+				xscom_write(p->chip_id, p->pci_stk_xscom +
+					    XPEC_PCI_STK_PCI_FIR, 0);
+				xscom_write(p->chip_id, p->pe_stk_xscom +
+					    XPEC_NEST_STK_PCI_NFIR, 0);
+			}
+
 			/* Clear PHB from reset */
 			xscom_write(p->chip_id,
 				    p->pci_stk_xscom + XPEC_PCI_STK_ETU_RESET, 0x0);
-- 
2.17.1