[linux-dvb] Re: setting voltage takes TONS of time

[Johannes Stezenbach <js@convergence.de>]

On Tue, Jul 30, 2002 at 02:53:42PM -0400, Jeremy Hall wrote:
> 
> I have discovered that an unmodified driver that is told to
> SEC_SET_VOLTAGE takes over 11ms to complete this task.
> 
> The two calls that seem to generate the most amount of time are:
> 
> setPids(0,0,0,0,0); // takes up to 3 or 4 ms
> 
> return SecSetVoltage(val); takes upwards of 7.5 ms.  Can you think of a
> reason for this to take so long? The kernel is 2.4.19-RC1 + ll + preempt +
> firm timers.  The low latency and preempt patches help overall execution
> of RT processes and firm timres helps with nanosleep, select, and other
> sleepy tasks.  Without these, you don't get adequate sleep time, you may
> overshoot by several ms.
> 
> thoughts?
> 
> This is with the HEAD CVS branch, not newstruct.

You did not tell us what DVB Card you use, but I suspect that the
preempt patch conflicts with the I2C driver which generates correct
timing with usleep() and msleep().

Does the driver work in your kernel without preempt patch?


Johannes


-- 
Info:
To unsubscribe send a mail to listar@linuxtv.org with "unsubscribe linux-dvb" as subject.