MTD: Provide XIP support for Intel flash chips.

This allows for MTD support to be used on flash memory which is also used
for XIP purposes, either XIP kernel or XIP userspace.  The whole idea is
to relocate functions actually modifying the flash state away from array mode
to ram and run them with interrupt disabled.  When the flash needs some time
to complete a certain operation, we poll the processor for pending (but still
masked) interrupts, and when they occur we suspend the flash operation in order
to unmask interrupts and let the system run again.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

2 files changed, 102 insertions, 1 deletions

diff --git a/include/linux/mtd/flashchip.h b/include/linux/mtd/flashchip.h
index c3ac4df7273f..c66ba812bf90 100644
--- a/include/linux/mtd/flashchip.h
+++ b/include/linux/mtd/flashchip.h
@@ -6,7 +6,7 @@
  *
  * (C) 2000 Red Hat. GPLd.
  *
- * $Id: flashchip.h,v 1.14 2004/06/15 16:44:59 nico Exp $
+ * $Id: flashchip.h,v 1.15 2004/11/05 22:41:06 nico Exp $
  *
  */
 
@@ -37,6 +37,8 @@ typedef enum {
 	FL_LOCKING,
 	FL_UNLOCKING,
 	FL_POINT,
+	FL_XIP_WHILE_ERASING,
+	FL_XIP_WHILE_WRITING,
 	FL_UNKNOWN
 } flstate_t;
 
diff --git a/include/linux/mtd/xip.h b/include/linux/mtd/xip.h
new file mode 100644
index 000000000000..521aa8e826ee
--- /dev/null
+++ b/include/linux/mtd/xip.h
@@ -0,0 +1,99 @@
+/*
+ * MTD primitives for XIP support
+ *
+ * Author:	Nicolas Pitre
+ * Created:	Nov 2, 2004
+ * Copyright:	(C) 2004 MontaVista Software, Inc.
+ *
+ * This XIP support for MTD has been loosely inspired
+ * by an earlier patch authored by David Woodhouse.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * $Id: xip.h,v 1.1 2004/11/05 22:41:06 nico Exp $
+ */
+
+#ifndef __LINUX_MTD_XIP_H__
+#define __LINUX_MTD_XIP_H__
+
+#include <linux/config.h>
+
+#ifdef CONFIG_MTD_XIP
+
+/*
+ * Function that are modifying the flash state away from array mode must
+ * obviously not be running from flash.  The __xipram is therefore marking
+ * those functions so they get relocated to ram.
+ */
+#define __xipram __attribute__ ((__section__ (".data")))
+
+/*
+ * We really don't want gcc to guess anything.
+ * We absolutely _need_ proper inlining.
+ */
+#include <linux/compiler.h>
+
+/*
+ * Each architecture has to provide the following macros.  They must access
+ * the hardware directly and not rely on any other (XIP) functions since they
+ * won't be available when used (flash not in array mode).
+ *
+ * xip_irqpending()
+ *
+ * 	return non zero when any hardware interrupt is pending.
+ *
+ * xip_currtime()
+ *
+ * 	return a platform specific time reference to be used with
+ * 	xip_elapsed_since().
+ *
+ * xip_elapsed_since(x)
+ *
+ * 	return in usecs the elapsed timebetween now and the reference x as
+ * 	returned by xip_currtime().
+ *
+ * 	note 1: convertion to usec can be approximated, as long as the
+ * 		returned value is <= the real elapsed time.
+ * 	note 2: this should be able to cope with a few seconds without
+ * 		overflowing.
+ */
+
+#if defined(CONFIG_ARCH_SA1100) || defined(CONFIG_ARCH_PXA)
+
+#include <asm/hardware.h>
+#ifdef CONFIG_ARCH_PXA
+#include <asm/arch/pxa-regs.h>
+#endif
+
+#define xip_irqpending()	(ICIP & ICMR)
+
+/* we sample OSCR and convert desired delta to usec (1/4 ~= 1000000/3686400) */
+#define xip_currtime()		(OSCR)
+#define xip_elapsed_since(x)	(signed)((OSCR - (x)) / 4)
+
+#else
+#error "missing IRQ and timer primitives for XIP MTD support"
+#endif
+
+/*
+ * xip_cpu_idle() is used when waiting for a delay equal or larger than
+ * the system timer tick period.  This should put the CPU into idle mode
+ * to save power and to be woken up only when some interrupts are pending.
+ * As above, this should not rely upon standard kernel code.
+ */
+
+#if defined(CONFIG_CPU_XSCALE)
+#define xip_cpu_idle()  asm volatile ("mcr p14, 0, %0, c7, c0, 0" :: "r" (1))
+#else
+#define xip_cpu_idle()  do { } while (0)
+#endif
+
+#else
+
+#define __xipram
+
+#endif /* CONFIG_MTD_XIP */
+
+#endif /* __LINUX_MTD_XIP_H__ */