ad1848: fix schedule while atomic, simplify MCE down code



The function snd_ad1848_mce_down() called msleep() while holding a spinlock

with IRQs disabled.



A polling loop to check for ACI to go down was more convoluted than it needed

to be.  New loop should be more efficient and it a lot simpler.



A polling loop to check for the device to leaving INIT mode is removed.  The

device must have already left init for the previous ACI loop to have finished.



Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>

diff -r 50502c13d2cf isa/ad1848/ad1848_lib.c
--- a/isa/ad1848/ad1848_lib.c	Mon Sep 17 19:08:32 2007 +0200
+++ b/isa/ad1848/ad1848_lib.c	Mon Sep 17 12:57:05 2007 -0700
@@ -205,7 +205,6 @@ static void snd_ad1848_mce_down(struct s
 {
 	unsigned long flags;
 	int timeout;
-	unsigned long end_time;
 
 	spin_lock_irqsave(&chip->reg_lock, flags);
 	for (timeout = 5; timeout > 0; timeout--)
@@ -231,39 +230,28 @@ static void snd_ad1848_mce_down(struct s
 		return;
 	}
 
-	/*
-	 * Wait for (possible -- during init auto-calibration may not be set)
-	 * calibration process to start. Needs upto 5 sample periods on AD1848
-	 * which at the slowest possible rate of 5.5125 kHz means 907 us.
+	/* 
+	 * Wait for auto-calibration (AC) process to finish, i.e. ACI to go
+	 * low.  It may take up to 5 sample periods (at most 907 us @ 5.5125
+	 * kHz) for the process to _start_, so it is important to wait at least
+	 * that long before checking.  Otherwise we might think AC has finished
+	 * when it has in fact not begun.  It should take 128 (no AC) or 384
+	 * (AC) cycles for ACI to drop.  This gives a range of at most 70 ms
+	 * with a more typical value of just under 3 ms.  With a 3 ms wait, we
+	 * will probably finish on the first loop.
 	 */
-	msleep(1);
-
-	snd_printdd("(2) jiffies = %lu\n", jiffies);
-
-	end_time = jiffies + msecs_to_jiffies(250);
-	while (snd_ad1848_in(chip, AD1848_TEST_INIT) & AD1848_CALIB_IN_PROGRESS) {
-		spin_unlock_irqrestore(&chip->reg_lock, flags);
-		if (time_after(jiffies, end_time)) {
-			snd_printk(KERN_ERR "mce_down - auto calibration time out (2)\n");
-			return;
-		}
-		msleep(1);
+	/* give up at ~1/4 sec at 3 ms per loop */
+ 	for(timeout = 85; timeout > 0; timeout--) {
+		msleep(3);
 		spin_lock_irqsave(&chip->reg_lock, flags);
-	}
-
-	snd_printdd("(3) jiffies = %lu\n", jiffies);
-
-	end_time = jiffies + msecs_to_jiffies(100);
-	while (inb(AD1848P(chip, REGSEL)) & AD1848_INIT) {
-		spin_unlock_irqrestore(&chip->reg_lock, flags);
-		if (time_after(jiffies, end_time)) {
-			snd_printk(KERN_ERR "mce_down - auto calibration time out (3)\n");
-			return;
-		}
-		msleep(1);
-		spin_lock_irqsave(&chip->reg_lock, flags);
-	}
-	spin_unlock_irqrestore(&chip->reg_lock, flags);
+		if (snd_ad1848_in(chip, AD1848_TEST_INIT) & AD1848_CALIB_IN_PROGRESS)
+			break;
+	}
+	spin_unlock_irqrestore(&chip->reg_lock, flags);
+	if (!timeout) {
+		snd_printk(KERN_ERR "mce_down - auto calibration time out (2)\n");
+		return;
+	}
 
 	snd_printdd("(4) jiffies = %lu\n", jiffies);
 	snd_printd("mce_down - exit = 0x%x\n", inb(AD1848P(chip, REGSEL)));