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

[Holger Waechtler <holger@convergence.de>]

Andrew de Quincey wrote:
> 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.
applied, please report if there're problems.

Holger


> ------------------------------------------------------------------------
>
> 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"));
>  		}
>  	}


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