Input: i8042 - try to get stable CTR value when initializing

If user presses keys while i8042 is being initialized there is a chance
that keyboard data will be mistaken for results of Read Control Register
command causing futher troubles. Work around this issue by reading CTR
several times and stop when we get matching results.

Reported-and-tested-by: Dave Young <[e-mail]>
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/serio/i8042.c

···
 static int i8042_controller_init(void)
 {
 	unsigned long flags;
+	int n = 0;
+	unsigned char ctr[2];
 
 /*
- * Save the CTR for restoral on unload / reboot.
+ * Save the CTR for restore on unload / reboot.
  */
 
-	if (i8042_command(&i8042_ctr, I8042_CMD_CTL_RCTR)) {
-		printk(KERN_ERR "i8042.c: Can't read CTR while initializing i8042.\n");
-		return -EIO;
-	}
+	do {
+		if (n >= 10) {
+			printk(KERN_ERR
+				"i8042.c: Unable to get stable CTR read.\n");
+			return -EIO;
+		}
 
-	i8042_initial_ctr = i8042_ctr;
+		if (n != 0)
+			udelay(50);
+
+		if (i8042_command(&ctr[n++ % 2], I8042_CMD_CTL_RCTR)) {
+			printk(KERN_ERR
+				"i8042.c: Can't read CTR while initializing i8042.\n");
+			return -EIO;
+		}
+
+	} while (n < 2 || ctr[0] != ctr[1]);
+
+	i8042_initial_ctr = i8042_ctr = ctr[0];
 
 /*
  * Disable the keyboard interface and interrupt.
···
 		return -EIO;
 	}
 
+/*
+ * Flush whatever accumulated while we were disabling keyboard port.
+ */
+
+	i8042_flush();
+
 	return 0;
 }
 
···
 	i8042_ctr |= I8042_CTR_KBDDIS | I8042_CTR_AUXDIS;
 	i8042_ctr &= ~(I8042_CTR_KBDINT | I8042_CTR_AUXINT);
 
-	if (i8042_command(&i8042_initial_ctr, I8042_CMD_CTL_WCTR))
+	if (i8042_command(&i8042_ctr, I8042_CMD_CTL_WCTR))
 		printk(KERN_WARNING "i8042.c: Can't write CTR while resetting.\n");
 
 /*