MIPS: CFE: Add cfe_die()

Add a cfe_die() implementation which is useful when the kernel does an
early panic and no console is registered. This allows us to print
useful diagnostics such as an invalid DTB having been
configured/selected.

Since the BMIPS_GENERIC kernel can be built with support for multiple
processors, we need to do a runtime determination of the type of CPU
that we are executing on to perform the appropriate XKS01 disabling.

Since cfe_init() + cfe_die() could be conceivably called at very early
stages of the kernel boot, before cpu_probe(), we do not rely on the
structure(s) populated by cpu_probe().

Signed-off-by: Florian Fainelli <[e-mail]>
Signed-off-by: Thomas Bogendoerfer <[e-mail]>

arch/mips/fw/cfe/cfe_api.c

···
  *
  * Authors:  Mitch Lichtenberg, Chris Demetriou
  */
-
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/printk.h>
+#include <asm/mipsregs.h>
 #include <asm/fw/cfe/cfe_api.h>
 #include "cfe_api_int.h"
+
+unsigned long __initdata cfe_seal;
 
 /* Cast from a native pointer to a cfe_xptr_t and back.	 */
 #define XPTR_FROM_NATIVE(n)	((cfe_xptr_t) (intptr_t) (n))
···
 	if (xiocb.xiocb_status < 0)
 		return xiocb.xiocb_status;
 	return xiocb.plist.xiocb_buffer.buf_retlen;
+}
+
+void __init cfe_die(char *fmt, ...)
+{
+	unsigned int prid, __maybe_unused rev;
+	char msg[128];
+	va_list ap;
+	int handle;
+	unsigned int count;
+
+	va_start(ap, fmt);
+	vsprintf(msg, fmt, ap);
+	strcat(msg, "\r\n");
+
+	if (cfe_seal != CFE_EPTSEAL)
+		goto no_cfe;
+
+	prid = read_c0_prid();
+	if ((prid & PRID_COMP_MASK) != PRID_COMP_BROADCOM)
+		goto no_cfe;
+
+	rev = prid & PRID_REV_MASK;
+
+	/* disable XKS01 so that CFE can access the registers */
+	switch (prid & PRID_IMP_MASK) {
+#ifdef CONFIG_CPU_BMIPS4380
+	case PRID_IMP_BMIPS43XX:
+		if (rev >= PRID_REV_BMIPS4380_LO &&
+		    rev <= PRID_REV_BMIPS4380_HI)
+			__write_32bit_c0_register($22, 3,
+				__read_32bit_c0_register($22, 3) & ~BIT(12));
+		break;
+#endif
+#ifdef CONFIG_CPU_BMIPS5000
+	case PRID_IMP_BMIPS5000:
+	case PRID_IMP_BMIPS5200:
+		__write_32bit_c0_register($22, 5,
+			__read_32bit_c0_register($22, 5) & ~BIT(8));
+		break;
+#endif
+	default:
+		break;
+	}
+
+	handle = cfe_getstdhandle(CFE_STDHANDLE_CONSOLE);
+	if (handle < 0)
+		goto no_cfe;
+
+	cfe_write(handle, msg, strlen(msg));
+
+	for (count = 0; count < 0x7fffffff; count++)
+		mb();
+	cfe_exit(0, 1);
+	while (1)
+		;
+
+no_cfe:
+	/* probably won't print anywhere useful */
+	panic("%s", msg);
+
+	va_end(ap);
 }

arch/mips/include/asm/fw/cfe/cfe_api.h

···
 int cfe_write(int handle, const char *buffer, int length);
 int cfe_writeblk(int handle, int64_t offset, const char *buffer,
 		 int length);
+extern unsigned long cfe_seal;
+__printf(1, 2) void cfe_die(char *fmt, ...);
 
 #endif				/* CFE_API_H */