[PATCH] x86 reboot: Add reboot fixup for gx1/cs5530a

This patch by Jaya Kumar introduces a generic infrastructure to deal with
x86 chipsets with nonstandard reset sequences, and adds support for the
Geode gx1/cs5530a chipset.

Signed-off-by: Jaya Kumar <jayalk@intworks.biz>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/Kconfig

@@ -653,6 +653,24 @@ config I8K
 	  Say Y if you intend to run this kernel on a Dell Inspiron 8000.
 	  Say N otherwise.
 
+config X86_REBOOTFIXUPS
+	bool "Enable X86 board specific fixups for reboot"
+	depends on X86
+	default n
+	---help---
+	  This enables chipset and/or board specific fixups to be done
+	  in order to get reboot to work correctly. This is only needed on
+	  some combinations of hardware and BIOS. The symptom, for which
+	  this config is intended, is when reboot ends with a stalled/hung
+	  system.
+
+	  Currently, the only fixup is for the Geode GX1/CS5530A/TROM2.1.
+	  combination.
+
+	  Say Y if you want to enable the fixup. Currently, it's safe to
+	  enable this option even if you don't need it.
+	  Say N otherwise.
+
 config MICROCODE
 	tristate "/dev/cpu/microcode - Intel IA32 CPU microcode support"
 	---help---

arch/i386/kernel/Makefile

@@ -23,6 +23,7 @@ obj-$(CONFIG_X86_TRAMPOLINE)	+= trampoline.o
 obj-$(CONFIG_X86_MPPARSE)	+= mpparse.o
 obj-$(CONFIG_X86_LOCAL_APIC)	+= apic.o nmi.o
 obj-$(CONFIG_X86_IO_APIC)	+= io_apic.o
+obj-$(CONFIG_X86_REBOOTFIXUPS)	+= reboot_fixups.o
 obj-$(CONFIG_X86_NUMAQ)		+= numaq.o
 obj-$(CONFIG_X86_SUMMIT_NUMA)	+= summit.o
 obj-$(CONFIG_KPROBES)		+= kprobes.o

arch/i386/kernel/reboot.c

@@ -13,6 +13,7 @@
 #include <asm/uaccess.h>
 #include <asm/apic.h>
 #include "mach_reboot.h"
+#include <linux/reboot_fixups.h>
 
 /*
  * Power off function, if any
@@ -348,6 +349,7 @@ void machine_restart(char * __unused)
 		/* rebooting needs to touch the page at absolute addr 0 */
 		*((unsigned short *)__va(0x472)) = reboot_mode;
 		for (;;) {
+			mach_reboot_fixups(); /* for board specific fixups */
 			mach_reboot();
 			/* That didn't work - force a triple fault.. */
 			__asm__ __volatile__("lidt %0": :"m" (no_idt));

arch/i386/kernel/reboot_fixups.c

@@ -0,0 +1,56 @@
+/*
+ * linux/arch/i386/kernel/reboot_fixups.c
+ *
+ * This is a good place to put board specific reboot fixups.
+ *
+ * List of supported fixups:
+ * geode-gx1/cs5530a - Jaya Kumar <jayalk@intworks.biz>
+ *
+ */
+
+#include <asm/delay.h>
+#include <linux/pci.h>
+
+static void cs5530a_warm_reset(struct pci_dev *dev)
+{
+	/* writing 1 to the reset control register, 0x44 causes the
+	cs5530a to perform a system warm reset */
+	pci_write_config_byte(dev, 0x44, 0x1);
+	udelay(50); /* shouldn't get here but be safe and spin-a-while */
+	return;
+}
+
+struct device_fixup {
+	unsigned int vendor;
+	unsigned int device;
+	void (*reboot_fixup)(struct pci_dev *);
+};
+
+static struct device_fixup fixups_table[] = {
+{ PCI_VENDOR_ID_CYRIX, PCI_DEVICE_ID_CYRIX_5530_LEGACY, cs5530a_warm_reset },
+};
+
+/*
+ * we see if any fixup is available for our current hardware. if there
+ * is a fixup, we call it and we expect to never return from it. if we
+ * do return, we keep looking and then eventually fall back to the
+ * standard mach_reboot on return.
+ */
+void mach_reboot_fixups(void)
+{
+	struct device_fixup *cur;
+	struct pci_dev *dev;
+	int i;
+
+	for (i=0; i < (sizeof(fixups_table)/sizeof(fixups_table[0])); i++) {
+		cur = &(fixups_table[i]);
+		dev = pci_get_device(cur->vendor, cur->device, 0);
+		if (!dev)
+			continue;
+
+		cur->reboot_fixup(dev);
+	}
+
+	printk(KERN_WARNING "No reboot fixup found for your hardware\n");
+}
+

include/linux/reboot_fixups.h

@@ -0,0 +1,10 @@
+#ifndef _LINUX_REBOOT_FIXUPS_H
+#define _LINUX_REBOOT_FIXUPS_H
+
+#ifdef CONFIG_X86_REBOOTFIXUPS
+extern void mach_reboot_fixups(void);
+#else
+#define mach_reboot_fixups() ((void)(0))
+#endif
+
+#endif /* _LINUX_REBOOT_FIXUPS_H */