[Gta04-owner] Host AP mode

Andreas Kemnade andreas at kemnade.info
Wed May 30 08:23:49 CEST 2012


On Tue, 29 May 2012 23:11:01 +0200
Christoph Mair <christoph.mair at gmail.com> wrote:

> > But my earlier mentioned wifi performance problem with 3.x, which does
> > not exist in 2.6.32, is not better with the libertas_tf driver.
> > Could the SD/MMC host driver be the bottleneck?
> I tried to debug the MMC interface and found out that the chip
> interface runs at 25MHz. I've read somewhere that the module should
> support up to 50MHz but I could not convince the module to use this
> speed. Anyways, 25MHz with a 4 bits wide interface should be enough
> for everyone [TM].
Hmm, that transfers the 640KByte, which are enough for everyone in
approx 50ms. Maybe people can live with that.
Does the data get collected from there in time? Are interrupts
correctly handled?

> Unfortunately I could not find out why the chip does not use higher
> data rates than 5MBit/s. I've seen very short periods where iwconfig
> displayed higher data rates (up to 48MBits/s) but the value returned
> immediately to 5MBits/s when I called iwconfig again (a few times).

The libertastf driver adjusts the bit rates to higher values but
that does not lead to higher data rates.

But why does the standard wifi driver in kernel 2.6.32 does not
have the problem? Does the improved power management in 3.x play a
role here?
The most interesting question is probably when the problem did start.
We know:
2.6.32: no problem
3.2, 3.3, 3.4: problem

Is that problem only with GTA04A4+Kernel3.x or also with GTA04A3+Kernel3.x?
What about the first 3.x kernels?  
How to bisect that problem? Do some minimal gta04 porting for the kernels,
so that only the most important devices work? 

Andreas Kemnade
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