[MTD] Fixes of performance and stability issues in CFI driver.

Fix of performance and stability issues on Intel NOR chips. It fixes:

1. Very low write performance on Sibley (perf tests demonstrated write
   performance less than 100Kb/sec when it should be over 400Kb/sec).

2. Low erase performance. (perf tests on Sibleuy demonstrated erase
   performance 246Kb/sec when it should be over 300Kb/sec).

3. Error on JFFS2 tests with CPU loading application when MTD returns
   "block erase error: (status timeout)" To fix the issue it does the
   following:
     1. Removes the timeout tuning from inval_cache_and_wait_for_operation.
     2. Waiting conditions in inval_cache_and_wait_for_operation now is
         based on timer resolution
        If timeout is lower than timer resolution then we do in cycle
	  "Checking the status"
	  udelay(1);
	  cond_resched();
        If timeout is greater than timer resolution (probably erase
        operation) We do the following
	  sleep for half of operation timeout and do in cycle the following
	    "Checking the status"
	    sleep for timer resolution

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

drivers/mtd/chips/cfi_cmdset_0001.c

@@ -908,7 +908,7 @@ static void __xipram xip_enable(struct map_info *map, struct flchip *chip,
 
 static int __xipram xip_wait_for_operation(
 		struct map_info *map, struct flchip *chip,
-		unsigned long adr, int *chip_op_time )
+		unsigned long adr, unsigned int chip_op_time )
 {
 	struct cfi_private *cfi = map->fldrv_priv;
 	struct cfi_pri_intelext *cfip = cfi->cmdset_priv;
@@ -917,7 +917,7 @@ static int __xipram xip_wait_for_operation(
 	flstate_t oldstate, newstate;
 
        	start = xip_currtime();
-	usec = *chip_op_time * 8;
+	usec = chip_op_time * 8;
 	if (usec == 0)
 		usec = 500000;
 	done = 0;
@@ -1027,8 +1027,8 @@ static int __xipram xip_wait_for_operation(
 #define XIP_INVAL_CACHED_RANGE(map, from, size)  \
 	INVALIDATE_CACHED_RANGE(map, from, size)
 
-#define INVAL_CACHE_AND_WAIT(map, chip, cmd_adr, inval_adr, inval_len, p_usec) \
-	xip_wait_for_operation(map, chip, cmd_adr, p_usec)
+#define INVAL_CACHE_AND_WAIT(map, chip, cmd_adr, inval_adr, inval_len, usec) \
+	xip_wait_for_operation(map, chip, cmd_adr, usec)
 
 #else
 
@@ -1040,64 +1040,64 @@ static int __xipram xip_wait_for_operation(
 static int inval_cache_and_wait_for_operation(
 		struct map_info *map, struct flchip *chip,
 		unsigned long cmd_adr, unsigned long inval_adr, int inval_len,
-		int *chip_op_time )
+		unsigned int chip_op_time)
 {
 	struct cfi_private *cfi = map->fldrv_priv;
 	map_word status, status_OK = CMD(0x80);
-	int z, chip_state = chip->state;
-	unsigned long timeo;
+	int chip_state = chip->state;
+	unsigned int timeo, sleep_time;
 
 	spin_unlock(chip->mutex);
 	if (inval_len)
 		INVALIDATE_CACHED_RANGE(map, inval_adr, inval_len);
-	if (*chip_op_time)
-		cfi_udelay(*chip_op_time);
 	spin_lock(chip->mutex);
 
-	timeo = *chip_op_time * 8 * HZ / 1000000;
-	if (timeo < HZ/2)
-		timeo = HZ/2;
-	timeo += jiffies;
+	/* set our timeout to 8 times the expected delay */
+	timeo = chip_op_time * 8;
+	if (!timeo)
+		timeo = 500000;
+	sleep_time = chip_op_time / 2;
 
-	z = 0;
 	for (;;) {
-		if (chip->state != chip_state) {
-			/* Someone's suspended the operation: sleep */
-			DECLARE_WAITQUEUE(wait, current);
-
-			set_current_state(TASK_UNINTERRUPTIBLE);
-			add_wait_queue(&chip->wq, &wait);
-			spin_unlock(chip->mutex);
-			schedule();
-			remove_wait_queue(&chip->wq, &wait);
-			timeo = jiffies + (HZ / 2); /* FIXME */
-			spin_lock(chip->mutex);
-			continue;
-		}
-
 		status = map_read(map, cmd_adr);
 		if (map_word_andequal(map, status, status_OK, status_OK))
 			break;
 
-		/* OK Still waiting */
-		if (time_after(jiffies, timeo)) {
+		if (!timeo) {
 			map_write(map, CMD(0x70), cmd_adr);
 			chip->state = FL_STATUS;
 			return -ETIME;
 		}
 
-		/* Latency issues. Drop the lock, wait a while and retry */
-		z++;
+		/* OK Still waiting. Drop the lock, wait a while and retry. */
 		spin_unlock(chip->mutex);
-		cfi_udelay(1);
+		if (sleep_time >= 1000000/HZ) {
+			/*
+			 * Half of the normal delay still remaining
+			 * can be performed with a sleeping delay instead
+			 * of busy waiting.
+			 */
+			msleep(sleep_time/1000);
+			timeo -= sleep_time;
+			sleep_time = 1000000/HZ;
+		} else {
+			udelay(1);
+			cond_resched();
+			timeo--;
+		}
 		spin_lock(chip->mutex);
-	}
 
-	if (!z) {
-		if (!--(*chip_op_time))
-			*chip_op_time = 1;
-	} else if (z > 1)
-		++(*chip_op_time);
+		if (chip->state != chip_state) {
+			/* Someone's suspended the operation: sleep */
+			DECLARE_WAITQUEUE(wait, current);
+			set_current_state(TASK_UNINTERRUPTIBLE);
+			add_wait_queue(&chip->wq, &wait);
+			spin_unlock(chip->mutex);
+			schedule();
+			remove_wait_queue(&chip->wq, &wait);
+			spin_lock(chip->mutex);
+		}
+	}
 
 	/* Done and happy. */
  	chip->state = FL_STATUS;
@@ -1107,8 +1107,7 @@ static int inval_cache_and_wait_for_operation(
 #endif
 
 #define WAIT_TIMEOUT(map, chip, adr, udelay) \
-	({ int __udelay = (udelay); \
-	   INVAL_CACHE_AND_WAIT(map, chip, adr, 0, 0, &__udelay); })
+	INVAL_CACHE_AND_WAIT(map, chip, adr, 0, 0, udelay);
 
 
 static int do_point_onechip (struct map_info *map, struct flchip *chip, loff_t adr, size_t len)
@@ -1332,7 +1331,7 @@ static int __xipram do_write_oneword(struct map_info *map, struct flchip *chip,
 
 	ret = INVAL_CACHE_AND_WAIT(map, chip, adr,
 				   adr, map_bankwidth(map),
-				   &chip->word_write_time);
+				   chip->word_write_time);
 	if (ret) {
 		xip_enable(map, chip, adr);
 		printk(KERN_ERR "%s: word write error (status timeout)\n", map->name);
@@ -1569,7 +1568,7 @@ static int __xipram do_write_buffer(struct map_info *map, struct flchip *chip,
 
 	ret = INVAL_CACHE_AND_WAIT(map, chip, cmd_adr,
 				   adr, len,
-				   &chip->buffer_write_time);
+				   chip->buffer_write_time);
 	if (ret) {
 		map_write(map, CMD(0x70), cmd_adr);
 		chip->state = FL_STATUS;
@@ -1704,7 +1703,7 @@ static int __xipram do_erase_oneblock(struct map_info *map, struct flchip *chip,
 
 	ret = INVAL_CACHE_AND_WAIT(map, chip, adr,
 				   adr, len,
-				   &chip->erase_time);
+				   chip->erase_time);
 	if (ret) {
 		map_write(map, CMD(0x70), adr);
 		chip->state = FL_STATUS;