[linux-dvb] tda1004x slow freq switch times

[Peter Siering <lists@siering.org>]

Hi,

there has been some discussion on slow channel switching times (>10s)
with a tda1004x frontend (Nova/Budget-T boards). I've compared two
different driver releases last night - where I started:

- dvb driver 1.0.x (pretty old I know): tuning fast, even when switching
frequency/transponder

- dvb driver 1.1.1+y (dvb-kernel from cvs for 2.4): tuning slow, when
switching frequency/transponder

here are my findings:

- if loading frontend module with tda1004x_debug with the newer driver I
see multiple calls(?) to tda1004x_set_frequency and very slow channel
switches (in VDR); if I use the old driver and set this option, I've
seen just one of those calls and switching is fast

- in a first attempt, I've tried to use the old frontend code with the
new driver, but had no success (switching slowly)

- afterwards I compared the dvb_frontend-code in 1.0.1 (cvs revision
1.55) with 1.1.1: there have been many changes since then so a
overhauled tuning code, but using the debug options did not get me any
further

- this morning I played around with a special option
"dvb_override_tune_delay" and voila: by changing this to 800 the time it
takes to switch frequency/transponder gets close to the old driver (most
of the time ;-)); I do not see multiple calls to tda1004x_set_frequency
anymore.

May someone confirm or reproduce this? (I've just tried it with one PC,
400 MHz PII)

Does this point to a problem in the tuning code?

Peter