[linux-dvb] Fix to the jerking problem with tda10045h

[Andrew de Quincey <adq_dvb@lidskialf.net>]

Hi, the jerking was caused by the i2c busyloop delays chewing too much CPU. 
The attached patch should fix it. 

Basically, I've made the i2c code use the busy-waiting-low-latency 
mdelay()/my_delay() combination if there is lots of data being transferred. 
Otherwise it just uses the high latency my_delay() code as previously.

Now for some soak testing.
Index: linux/drivers/media/common/saa7146_i2c.c
===================================================================
RCS file: /cvs/linuxtv/dvb-kernel/linux/drivers/media/common/saa7146_i2c.c,v
retrieving revision 1.19
diff -u -p -r1.19 saa7146_i2c.c
--- linux/drivers/media/common/saa7146_i2c.c	14 Jun 2003 20:06:03 -0000	1.19
+++ linux/drivers/media/common/saa7146_i2c.c	16 Jun 2003 10:37:18 -0000
@@ -187,7 +187,7 @@ int saa7146_i2c_reset(struct saa7146_dev
    it returns 0 if ok, -1 if the transfer failed, -2 if the transfer
    failed badly (e.g. address error) */
 static
-int saa7146_i2c_writeout(struct saa7146_dev *dev, u32* dword)
+int saa7146_i2c_writeout(struct saa7146_dev *dev, u32* dword, int short_delay)
 {
 	u32 status = 0, mc2 = 0;
 	int trial = 0;
@@ -245,7 +245,7 @@ int saa7146_i2c_writeout(struct saa7146_
 				DEB_I2C(("saa7146_i2c_writeout: timed out waiting for end of xfer\n"));
 				return -EIO;
 			}
-			if (++trial < 10)
+			if ((++trial < 20) && short_delay)
 				udelay(10);
 			else
 				my_wait(dev,1);
@@ -290,6 +290,7 @@ int saa7146_i2c_transfer(struct saa7146_
 	u32* buffer = dev->d_i2c.cpu_addr;
 	int err = 0;
         int address_err = 0;
+        int short_delay = 0;
 	
 	if (down_interruptible (&dev->i2c_lock))
 		return -ERESTARTSYS;
@@ -305,6 +306,8 @@ int saa7146_i2c_transfer(struct saa7146_
 		goto out;
 	}
 
+        if (count > 3) short_delay = 1;
+  
 	do {
 		/* reset the i2c-device if necessary */
 		err = saa7146_i2c_reset(dev);
@@ -315,7 +318,7 @@ int saa7146_i2c_transfer(struct saa7146_
 
 		/* write out the u32s one after another */
 		for(i = 0; i < count; i++) {
-			err = saa7146_i2c_writeout(dev, &buffer[i] );
+			err = saa7146_i2c_writeout(dev, &buffer[i], short_delay);
 			if ( 0 != err) {
 				/* this one is unsatisfying: some i2c slaves on some
 				   dvb cards don't acknowledge correctly, so the saa7146
@@ -370,7 +373,7 @@ out:
 	if( 0 == dev->revision ) {
 		u32 zero = 0;
 		saa7146_i2c_reset(dev);
-		if( 0 != saa7146_i2c_writeout(dev, &zero)) {
+		if( 0 != saa7146_i2c_writeout(dev, &zero, short_delay)) {
 			INFO(("revision 0 error. this should never happen.\n"));
 		}
 	}