[linux-dvb] Re: Erroneous unsupported PLL synthesizer: foundit!!

[Michael Hunold <hunold-ml@web.de>]

Hello Holger, hello Andrew,

> > Here you are.. this should also still report address errors correctly.
> looks good,
This change is not as good as it looks. It may work on dvb cards 
perfectly, but it has negative side effects on my analog saa7146 based 
cards.

For example, the video muxes (tea6415c), audio muxes (tea6420) and the 
tuners may be present on very different i2c addresses, depending what 
the engineer has chosen. Because of the fact, that the mxb driver for 
example cannot specify on which addresses it expects this devices to be, 
it uses intesive probing.

Your change now retransmits these probe i2c messages for 3 retries, even 
if the first one has already shown that the device is not there (address 
error). This greatly increases the time the driver needs for loading, 
from about 1 seconds to 5 seconds.

> but I wonder if we shouldn't add a delay'n'retry on adress 
> error for the current message only...
> (imagine the stv0299 i2c gate case: 1st msg is opening the gate, then 
> the second message has to wait a bit, but we don't want to resend the 
> entire message...)
The problem is the crappy i2c behaviour of these chipsets. I mean, i2c 
is such a simple protocol and nevertheless some engineers "succeed" in 
screwing it up. 8-/

> Anyway, I applied your patch to CVS, further optimisations can follow 
> later.
I modified it the following way: currently, all analog saa7146 based 
cards use i2c transactions with i2c irqs enabled, for better 
performance. dvb cards don't use this, since it screws up gpio/debi irqs 
and results in "gpio oops"/"debi oops" messages and ts lockup.

So your new address error behaviour is only chosen for cards that don't 
use i2c irqs (0!= SAA7146_USE_I2C_IRQ & dev->ext->flags). So dvb cards 
get the new behaviour, analog cards have the old behaviour back. Ok?

> Holger
CU
Michael.



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