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>

drivers/mtd/chips/Kconfig

 # drivers/mtd/chips/Kconfig
-# $Id: Kconfig,v 1.9 2004/07/16 15:32:14 dwmw2 Exp $
+# $Id: Kconfig,v 1.10 2004/11/05 22:41:04 nico Exp $
 
 menu "RAM/ROM/Flash chip drivers"
 	depends on MTD!=n
@@ -272,5 +272,14 @@ config MTD_JEDEC
 	  <http://www.jedec.org/> distributes the identification codes for the
 	  chips.
 
+config MTD_XIP
+	bool "XIP aware MTD support"
+	depends on !SMP && MTD_CFI_INTELEXT && EXPERIMENTAL
+	default y if XIP_KERNEL
+	help
+	  This allows MTD support to work with flash memory which is also
+	  used for XIP purposes.  If you're not sure what this is all about
+	  then say N.
+
 endmenu
 

drivers/mtd/chips/cfi_probe.c

 /* 
    Common Flash Interface probe code.
    (C) 2000 Red Hat. GPL'd.
-   $Id: cfi_probe.c,v 1.79 2004/10/20 23:04:01 dwmw2 Exp $
+   $Id: cfi_probe.c,v 1.83 2004/11/16 18:19:02 nico Exp $
 */
 
 #include <linux/config.h>
@@ -15,6 +15,7 @@
 #include <linux/slab.h>
 #include <linux/interrupt.h>
 
+#include <linux/mtd/xip.h>
 #include <linux/mtd/map.h>
 #include <linux/mtd/cfi.h>
 #include <linux/mtd/gen_probe.h>
@@ -31,11 +32,47 @@ static int cfi_chip_setup(struct map_info *map, struct cfi_private *cfi);
 
 struct mtd_info *cfi_probe(struct map_info *map);
 
+#ifdef CONFIG_MTD_XIP
+
+/* only needed for short periods, so this is rather simple */
+#define xip_disable()	local_irq_disable()
+
+#define xip_allowed(base, map) \
+do { \
+	(void) map_read(map, base); \
+	asm volatile (".rep 8; nop; .endr"); \
+	local_irq_enable(); \
+} while (0)
+
+#define xip_enable(base, map, cfi) \
+do { \
+	cfi_send_gen_cmd(0xF0, 0, base, map, cfi, cfi->device_type, NULL); \
+	cfi_send_gen_cmd(0xFF, 0, base, map, cfi, cfi->device_type, NULL); \
+	xip_allowed(base, map); \
+} while (0)
+
+#define xip_disable_qry(base, map, cfi) \
+do { \
+	xip_disable(); \
+	cfi_send_gen_cmd(0xF0, 0, base, map, cfi, cfi->device_type, NULL); \
+	cfi_send_gen_cmd(0xFF, 0, base, map, cfi, cfi->device_type, NULL); \
+	cfi_send_gen_cmd(0x98, 0x55, base, map, cfi, cfi->device_type, NULL); \
+} while (0)
+
+#else
+
+#define xip_disable()			do { } while (0)
+#define xip_allowed(base, map)		do { } while (0)
+#define xip_enable(base, map, cfi)	do { } while (0)
+#define xip_disable_qry(base, map, cfi) do { } while (0)
+
+#endif
+
 /* check for QRY.
    in: interleave,type,mode
    ret: table index, <0 for error
  */
-static int qry_present(struct map_info *map, __u32 base,
+static int __xipram qry_present(struct map_info *map, __u32 base,
 				struct cfi_private *cfi)
 {
 	int osf = cfi->interleave * cfi->device_type;	// scale factor
@@ -59,10 +96,10 @@ static int qry_present(struct map_info *map, __u32 base,
 	if (!map_word_equal(map, qry[2], val[2]))
 		return 0;
 
-	return 1; 	// nothing found
+	return 1; 	// "QRY" found
 }
 
-static int cfi_probe_chip(struct map_info *map, __u32 base,
+static int __xipram cfi_probe_chip(struct map_info *map, __u32 base,
 				   unsigned long *chip_map, struct cfi_private *cfi)
 {
 	int i;
@@ -79,12 +116,16 @@ static int cfi_probe_chip(struct map_info *map, __u32 base,
 			(unsigned long)base + 0x55, map->size -1);
 		return 0;
 	}
+
+	xip_disable();
 	cfi_send_gen_cmd(0xF0, 0, base, map, cfi, cfi->device_type, NULL);
 	cfi_send_gen_cmd(0xFF, 0, base, map, cfi, cfi->device_type, NULL);
 	cfi_send_gen_cmd(0x98, 0x55, base, map, cfi, cfi->device_type, NULL);
 
-	if (!qry_present(map,base,cfi))
+	if (!qry_present(map,base,cfi)) {
+		xip_enable(base, map, cfi);
 		return 0;
+	}
 
 	if (!cfi->numchips) {
 		/* This is the first time we're called. Set up the CFI 
@@ -110,6 +151,7 @@ static int cfi_probe_chip(struct map_info *map, __u32 base,
 
 			/* If the QRY marker goes away, it's an alias */
 			if (!qry_present(map, start, cfi)) {
+				xip_allowed(base, map);
 				printk(KERN_DEBUG "%s: Found an alias at 0x%x for the chip at 0x%lx\n",
 				       map->name, base, start);
 				return 0;
@@ -122,6 +164,7 @@ static int cfi_probe_chip(struct map_info *map, __u32 base,
 			cfi_send_gen_cmd(0xFF, 0, start, map, cfi, cfi->device_type, NULL);
 			
 			if (qry_present(map, base, cfi)) {
+				xip_allowed(base, map);
 				printk(KERN_DEBUG "%s: Found an alias at 0x%x for the chip at 0x%lx\n",
 				       map->name, base, start);
 				return 0;
@@ -137,6 +180,7 @@ static int cfi_probe_chip(struct map_info *map, __u32 base,
 	/* Put it back into Read Mode */
 	cfi_send_gen_cmd(0xF0, 0, base, map, cfi, cfi->device_type, NULL);
 	cfi_send_gen_cmd(0xFF, 0, base, map, cfi, cfi->device_type, NULL);
+	xip_allowed(base, map);
 
 	printk(KERN_INFO "%s: Found %d x%d devices at 0x%x in %d-bit bank\n",
 	       map->name, cfi->interleave, cfi->device_type*8, base,
@@ -145,7 +189,7 @@ static int cfi_probe_chip(struct map_info *map, __u32 base,
 	return 1;
 }
 
-static int cfi_chip_setup(struct map_info *map, 
+static int __xipram cfi_chip_setup(struct map_info *map, 
 				   struct cfi_private *cfi)
 {
 	int ofs_factor = cfi->interleave*cfi->device_type;
@@ -153,6 +197,7 @@ static int cfi_chip_setup(struct map_info *map,
 	int num_erase_regions = cfi_read_query(map, base + (0x10 + 28)*ofs_factor);
 	int i;
 
+	xip_enable(base, map, cfi);
 #ifdef DEBUG_CFI
 	printk("Number of erase regions: %d\n", num_erase_regions);
 #endif
@@ -170,9 +215,29 @@ static int cfi_chip_setup(struct map_info *map,
 	cfi->cfi_mode = CFI_MODE_CFI;
 	
 	/* Read the CFI info structure */
-	for (i=0; i<(sizeof(struct cfi_ident) + num_erase_regions * 4); i++) {
+	xip_disable_qry(base, map, cfi);
+	for (i=0; i<(sizeof(struct cfi_ident) + num_erase_regions * 4); i++)
 		((unsigned char *)cfi->cfiq)[i] = cfi_read_query(map,base + (0x10 + i)*ofs_factor);
-	}
+
+	/* Note we put the device back into Read Mode BEFORE going into Auto
+	 * Select Mode, as some devices support nesting of modes, others
+	 * don't. This way should always work.
+	 * On cmdset 0001 the writes of 0xaa and 0x55 are not needed, and
+	 * so should be treated as nops or illegal (and so put the device
+	 * back into Read Mode, which is a nop in this case).
+	 */
+	cfi_send_gen_cmd(0xf0,     0, base, map, cfi, cfi->device_type, NULL);
+	cfi_send_gen_cmd(0xaa, 0x555, base, map, cfi, cfi->device_type, NULL);
+	cfi_send_gen_cmd(0x55, 0x2aa, base, map, cfi, cfi->device_type, NULL);
+	cfi_send_gen_cmd(0x90, 0x555, base, map, cfi, cfi->device_type, NULL);
+	cfi->mfr = cfi_read_query(map, base);
+	cfi->id = cfi_read_query(map, base + ofs_factor);    
+
+	/* Put it back into Read Mode */
+	cfi_send_gen_cmd(0xF0, 0, base, map, cfi, cfi->device_type, NULL);
+	/* ... even if it's an Intel chip */
+	cfi_send_gen_cmd(0xFF, 0, base, map, cfi, cfi->device_type, NULL);
+	xip_allowed(base, map);
 
 	/* Do any necessary byteswapping */
 	cfi->cfiq->P_ID = le16_to_cpu(cfi->cfiq->P_ID);
@@ -198,25 +263,6 @@ static int cfi_chip_setup(struct map_info *map,
 #endif
 	}
 
-	/* Note we put the device back into Read Mode BEFORE going into Auto
-	 * Select Mode, as some devices support nesting of modes, others
-	 * don't. This way should always work.
-	 * On cmdset 0001 the writes of 0xaa and 0x55 are not needed, and
-	 * so should be treated as nops or illegal (and so put the device
-	 * back into Read Mode, which is a nop in this case).
-	 */
-	cfi_send_gen_cmd(0xf0,     0, base, map, cfi, cfi->device_type, NULL);
-	cfi_send_gen_cmd(0xaa, 0x555, base, map, cfi, cfi->device_type, NULL);
-	cfi_send_gen_cmd(0x55, 0x2aa, base, map, cfi, cfi->device_type, NULL);
-	cfi_send_gen_cmd(0x90, 0x555, base, map, cfi, cfi->device_type, NULL);
-	cfi->mfr = cfi_read_query(map, base);
-	cfi->id = cfi_read_query(map, base + ofs_factor);    
-
-	/* Put it back into Read Mode */
-	cfi_send_gen_cmd(0xF0, 0, base, map, cfi, cfi->device_type, NULL);
-	/* ... even if it's an Intel chip */
-	cfi_send_gen_cmd(0xFF, 0, base, map, cfi, cfi->device_type, NULL);
-
 	printk(KERN_INFO "%s: Found %d x%d devices at 0x%x in %d-bit bank\n",
 	       map->name, cfi->interleave, cfi->device_type*8, base,
 	       map->bankwidth*8);

drivers/mtd/chips/cfi_util.c

@@ -7,7 +7,7 @@
  *
  * This code is covered by the GPL.
  *
- * $Id: cfi_util.c,v 1.5 2004/08/12 06:40:23 eric Exp $
+ * $Id: cfi_util.c,v 1.7 2004/11/05 22:41:05 nico Exp $
  *
  */
 
@@ -22,13 +22,14 @@
 #include <linux/slab.h>
 #include <linux/delay.h>
 #include <linux/interrupt.h>
+#include <linux/mtd/xip.h>
 #include <linux/mtd/mtd.h>
 #include <linux/mtd/map.h>
 #include <linux/mtd/cfi.h>
 #include <linux/mtd/compatmac.h>
 
 struct cfi_extquery *
-cfi_read_pri(struct map_info *map, __u16 adr, __u16 size, const char* name)
+__xipram cfi_read_pri(struct map_info *map, __u16 adr, __u16 size, const char* name)
 {
 	struct cfi_private *cfi = map->fldrv_priv;
 	__u32 base = 0; // cfi->chips[0].start;
@@ -40,21 +41,35 @@ cfi_read_pri(struct map_info *map, __u16 adr, __u16 size, const char* name)
 	if (!adr)
 		goto out;
 
-	/* Switch it into Query Mode */
-	cfi_send_gen_cmd(0x98, 0x55, base, map, cfi, cfi->device_type, NULL);
-
 	extp = kmalloc(size, GFP_KERNEL);
 	if (!extp) {
 		printk(KERN_ERR "Failed to allocate memory\n");
 		goto out;
 	}
 
+#ifdef CONFIG_MTD_XIP
+	local_irq_disable();
+#endif
+
+	/* Switch it into Query Mode */
+	cfi_send_gen_cmd(0x98, 0x55, base, map, cfi, cfi->device_type, NULL);
+
 	/* Read in the Extended Query Table */
 	for (i=0; i<size; i++) {
 		((unsigned char *)extp)[i] = 
 			cfi_read_query(map, base+((adr+i)*ofs_factor));
 	}
 
+	/* Make sure it returns to read mode */
+	cfi_send_gen_cmd(0xf0, 0, base, map, cfi, cfi->device_type, NULL);
+	cfi_send_gen_cmd(0xff, 0, base, map, cfi, cfi->device_type, NULL);
+
+#ifdef CONFIG_MTD_XIP
+	(void) map_read(map, base);
+	asm volatile (".rep 8; nop; .endr");
+	local_irq_enable();
+#endif
+
 	if (extp->MajorVersion != '1' || 
 	    (extp->MinorVersion < '0' || extp->MinorVersion > '3')) {
 		printk(KERN_WARNING "  Unknown %s Extended Query "
@@ -62,15 +77,9 @@ cfi_read_pri(struct map_info *map, __u16 adr, __u16 size, const char* name)
 		       extp->MinorVersion);
 		kfree(extp);
 		extp = NULL;
-		goto out;
 	}
 
-out:
-	/* Make sure it's in read mode */
-	cfi_send_gen_cmd(0xf0, 0, base, map, cfi, cfi->device_type, NULL);
-	cfi_send_gen_cmd(0xff, 0, base, map, cfi, cfi->device_type, NULL);
-
-	return extp;
+ out:	return extp;
 }
 
 EXPORT_SYMBOL(cfi_read_pri);

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;
 

include/linux/mtd/xip.h

+/*
+ * 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__ */