[linux-dvb] Re: timing in dvb-kernel

[Michael Hunold <hunold@convergence.de>]

Hello Oliver,

> This requires two modifications:
> [1] I committed a change to 'dvb-kernel' which increases speed of the
>     I2C bus for *full-featured* cards to 275 kHz (same value as in DVB).
>     Please update file av7110.c from dvb-kernel CVS.
>
> [2] Apply the following patch to saa7146_i2c.c:
>
> -----------------  snip  ----------------------------
> diff -p -u -r1.26 saa7146_i2c.c
> --- saa7146_i2c.c	14 Nov 2003 11:42:04 -0000	1.26
> +++ saa7146_i2c.c	25 Nov 2003 03:29:29 -0000
> @@ -301,7 +301,7 @@ int saa7146_i2c_transfer(struct saa7146_
>  		goto out;
>  	}
>  
> -        if (count > 3) short_delay = 1;
> +        short_delay = 1; // OE test
>    
>  	do {
>  		/* reset the i2c-device if necessary */
> -----------------  snip  ----------------------------
>
> Note that without [2] modification [1] is almost useless,
> because each I2C access causes a delay of 10..20ms.
> I suggested several times to improve this but I was ignored...
I'm sorry if I ignored something back then. I just had a look at our 
discussion and it thought that the discussion was about the DVB driver only.

Please repeat your proposal.

In your other mail your wrote:

> The problem is that the saa7146 driver is used by different types of
> cards. IMHO we need a way to select whether short_delay should be used
> in the saa7146 driver or not.

"struct saa7146_extension" in "include/media/saa7146.h" already has a 
flag SAA7146_USE_I2C_IRQ for i2c driven i2c for analog tv cards.

You could simply add a SAA7146_I2C_SHORT_DELAY flag here and check for 
it saa7146_i2c_writeout() like this:

if( 0 != (SAA7146_I2C_SHORT_DELAY & dev->ext->flags)) {
	short_delay = 1;
}
[...]

> Oliver
CU
Michael.



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