[Skiboot] [RFC] phb4: Wait for PRD to reset the CAPP Fir during recovery

[Vaibhav Jain]

During CAPP recovery do_capp_recovery_scoms() will reset the CAPP Fir
register just after CAPP recovery is completed. This has an
unintentional side effect of preventing PRD from analyzing and
reporting this error. If PRD tries to read the CAPP FIR after opal has
already reset it, then it logs a critical error complaining "No active
error bits found".

To prevent this from happening we update do_capp_recovery_scoms() to
wait for CAPP Fir to be reset by PRD just after CAPP recovery
completes and before we proceed with rest of the CAPP recovery
sequence. A timeout of 5ms is used to wait for CAPP-Fir reset before
we reset the register on our own. This is to guard against the
possibility of Opal PRD daemon crashing/not-running.

Signed-off-by: Vaibhav Jain <vaibhav at linux.ibm.com>
---
 hw/phb4.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/hw/phb4.c b/hw/phb4.c
index 10df206b..bb95a953 100644
--- a/hw/phb4.c
+++ b/hw/phb4.c
@@ -3055,7 +3055,24 @@ static int do_capp_recovery_scoms(struct phb4 *p)
 
 	/* Check if the recovery failed or passed */
 	if (reg & PPC_BIT(1)) {
+
+		PHBDBG(p, "Waiting for FIR to reset\n");
+
+		/* Wait for FIR to be reset by PRD */
+		end = mftb() + msecs_to_tb(5);
+		do {
+			xscom_read(p->chip_id, CAPP_FIR + offset, &reg);
+			time_wait_us(100);
+			if (tb_compare(mftb(), end) != TB_ABEFOREB) {
+				PHBERR(p, "CAPP: Capp FIR reset Timed-out.\n");
+				break;
+			}
+		} while (reg);
+
 		PHBDBG(p, "Doing CAPP recovery scoms\n");
+		/* clear capp fir */
+		xscom_write(p->chip_id, CAPP_FIR + offset, 0);
+
 		/* disable snoops */
 		xscom_write(p->chip_id, SNOOP_CAPI_CONFIG + offset, 0);
 		load_capp_ucode(p);
@@ -3063,9 +3080,6 @@ static int do_capp_recovery_scoms(struct phb4 *p)
 		/* clear err rpt reg*/
 		xscom_write(p->chip_id, CAPP_ERR_RPT_CLR + offset, 0);
 
-		/* clear capp fir */
-		xscom_write(p->chip_id, CAPP_FIR + offset, 0);
-
 		/* Just reset Bit-0,1 and dont touch any other bit */
 		xscom_read(p->chip_id, CAPP_ERR_STATUS_CTRL + offset, &reg);
 		reg &= ~(PPC_BIT(0) | PPC_BIT(1));
-- 
2.17.2