[PATCH 27/38] MIPS: SGI-IP27: dispatch the early console between IOC3 and IOC4

[Imre Kaloz <kaloz@kernel.org>]

ip27-console.c casts the console UART to struct ioc3 unconditionally,
wrong for a Tezro's IOC4, whose UARTs sit at other offsets.

console_t.type reads back 0x0300fafa there, neither chip's PCI id, so on
IP35 dispatch on uart_base, which both chips populate correctly. A Hub
keeps the IOC3 path.

Signed-off-by: Imre Kaloz <kaloz@kernel.org>
---
 arch/mips/sgi-ip27/ip27-console.c | 47 ++++++++++++++++++++++++++++++-
 1 file changed, 46 insertions(+), 1 deletion(-)

diff --git a/arch/mips/sgi-ip27/ip27-console.c b/arch/mips/sgi-ip27/ip27-console.c
index 7737a88c6569..a1bcb4376f66 100644
--- a/arch/mips/sgi-ip27/ip27-console.c
+++ b/arch/mips/sgi-ip27/ip27-console.c
@@ -12,6 +12,7 @@
 #include <asm/sn/agent.h>
 #include <asm/sn/klconfig.h>
 #include <asm/sn/ioc3.h>
+#include <asm/sn/ioc4.h>
 
 #include <linux/serial.h>
 #include <linux/serial_core.h>
@@ -32,9 +33,53 @@ static inline struct ioc3_uartregs *console_uart(void)
 	return &ioc3->sregs.uarta;
 }
 
+/*
+ * On IP35 a Tezro drives its console off IOC4, a Fuel off IOC3.
+ * console_t.type cannot tell them apart -- a Tezro reads it back as
+ * 0x0300fafa, which is neither chip's PCI id -- while uart_base is
+ * populated on both, so dispatch on whether that lands on IOC3's own UART.
+ */
+static inline bool console_is_ioc4(nasid_t nasid)
+{
+	unsigned long uart_base;
+
+	if (!system_is_ip35)
+		return false;
+
+	uart_base = KL_CONFIG_CH_CONS_INFO(nasid)->uart_base;
+	if (!uart_base)
+		return false;
+
+	/* NODE_SWIN_ADDR() aliases widget 0 away; the console sits on 0xf. */
+	if (uart_base < RAW_NODE_SWIN_BASE(nasid, 0) ||
+	    uart_base >= RAW_NODE_SWIN_BASE(nasid, SWIN_WIDGET_MASK) +
+			 SWIN_SIZE)
+		return false;
+
+	return uart_base != (unsigned long)console_uart();
+}
+
+static inline struct ioc4_uartregs *console_uart_ioc4(nasid_t nasid)
+{
+	return (struct ioc4_uartregs *)KL_CONFIG_CH_CONS_INFO(nasid)->uart_base;
+}
+
 void prom_putchar(char c)
 {
-	struct ioc3_uartregs *uart = console_uart();
+	struct ioc3_uartregs *uart;
+	nasid_t nasid;
+
+	nasid = (master_nasid == INVALID_NASID) ? get_nasid() : master_nasid;
+	if (console_is_ioc4(nasid)) {
+		struct ioc4_uartregs *ioc4_uart = console_uart_ioc4(nasid);
+
+		while ((readb(&ioc4_uart->i4u_lsr) & 0x20) == 0)
+			;
+		writeb(c, &ioc4_uart->i4u_thr);
+		return;
+	}
+
+	uart = console_uart();
 
 	while ((readb(&uart->iu_lsr) & 0x20) == 0)
 		;
-- 
2.47.3