[Skiboot] [PATCH] hw/port80: Squash No SYNC error

[Oliver O'Halloran]

On Aspeed BMCs can be configured to route LPC IO address 0x80 to a GPIO
port. Some systems use this to implement a boot progress indicator, but
not all of them.

There's no easy way to tell if this has been setup or not and if it
hasn't we get an LPC SYNC no-response error from out LPC master. When we
reach Linux and enable interrupts this results in this spurious error
being printed:

    LPC[000]: Got SYNC no-response error. Error address reg: 0xd0010082

lpc_probe_write() is intended to catch situations where the peripherial
being written to might not be configured, so use that instead of
lpc_outb() to squash the error.

Cc: Ranga <stewart at flamingspork.com>
Cc: Andrew Jeffery <andrew at aj.id.au>
Signed-off-by: Oliver O'Halloran <oohall at gmail.com>
---
Stewart, do you know what systems actually implment this feature?
Seem like you added op_display_lpc() to add the BMC systems, but
I'm guessing only a few of them actually support it.
---
 hw/lpc-port80h.c      | 7 ++++---
 hw/test/run-port80h.c | 5 ++++-
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/hw/lpc-port80h.c b/hw/lpc-port80h.c
index eb1378c8ad2b..b373af7bcc8f 100644
--- a/hw/lpc-port80h.c
+++ b/hw/lpc-port80h.c
@@ -164,9 +164,10 @@ void op_display_lpc(enum op_severity s, enum op_module m, uint16_t c)
 		return;
 
 	port80_val = op_display_to_port80(port80_val, s, m, c);
-	lpc_outb(port80_val, 0x80);
 	port8x_val = op_display_to_port8x(port8x_val, s, m, c);
-	lpc_outb(port8x_val >> 8, 0x81);
-	lpc_outb(port8x_val & 0xFF, 0x82);
+
+	lpc_probe_write(OPAL_LPC_IO, 0x80, port80_val,        1);
+	lpc_probe_write(OPAL_LPC_IO, 0x81, port8x_val >> 8,   1);
+	lpc_probe_write(OPAL_LPC_IO, 0x82, port8x_val & 0xff, 1);
 }
 
diff --git a/hw/test/run-port80h.c b/hw/test/run-port80h.c
index 85e8d8721244..4964f4836ba8 100644
--- a/hw/test/run-port80h.c
+++ b/hw/test/run-port80h.c
@@ -15,15 +15,18 @@
 uint8_t port80;
 uint16_t port8x;
 
-static inline void lpc_outb(uint8_t data, uint32_t addr)
+static int64_t lpc_probe_write(int addr_type __unused, uint32_t addr,
+                        uint32_t data, uint32_t sz)
 {
 	assert((addr - 0x80) <= 2);
+	assert(sz == 1);
 	if (addr == 0x80)
 		port80 = data;
 	if (addr == 0x81)
 		port8x = data << 8 | (port8x & 0xff);
 	if (addr == 0x82)
 		port8x = (port8x & 0xff00) | data;
+	return 0;
 }
 
 #include "op-panel.h"
-- 
2.21.0