Re: [ath5k-devel] [PATCH v2] ath5k: fix I/Q calibration (for real)

[Bruno Randolf <br1@einfach.org>]

On Monday 08 March 2010 12:56:52 Luis R. Rodriguez wrote:
> On Sun, Mar 7, 2010 at 6:59 PM, Bruno Randolf <br1@einfach.org> wrote:
> > I/Q calibration was completely broken, resulting in a high number of CRC
> > errors on received packets. before i could see around 10% to 20% CRC
> > errors, with this patch they are between 0% and 3%.
> > 
> > 1.) the removal of the mask in commit "ath5k: Fix I/Q calibration
> > (f1cf2dbd0f798b71b1590e7aca6647f2caef1649)" resulted in no mask beeing
> > used when writing the I/Q values into the register. additional errors in
> > the calculation of the values (see 2.) resulted too high numbers,
> > exceeding the masks, so wrong values like 0xfffffffe were written. to be
> > safe we should always use the bitmask when writing parts of a register.
> > 
> > 2.) using a (s32) cast for q_coff is a wrong conversion to signed, since
> > we convert to a signed value later by substracting 128. this resulted in
> > too low numbers for Q many times, which were limited to -16 by the
> > boundary check later on.
> > 
> > 3.) checked everything against the HAL sources and took over comments and
> > minor optimizations from there.
> > 
> > 4.) we can't use ENABLE_BITS when we want to write a number (the number
> > can contain zeros). also always write the correction values first and
> > set ENABLE bit last, like the HAL does.
> > 
> > Signed-off-by: Bruno Randolf <br1@einfach.org>
> > ---
> > v2: use clamp() as Bob suggested
> 
> Thanks Bruno, are these stable fixes?

hi luis!

i think so. the behaviour before was completely broken, now it's better.

but i'm not sure about that whole Cc: stable@kernel.org thing... (sorry i've 
been away for a while)... i read Documentation/stable_kernel_rules.txt but 
still not sure if that applies for this patch.

given the current state of ath5k (which is usable but far from being perfect 
or performant) i think it does not really matter if this or any other of my 
fixes go into stable quickly or not... anyhow i personally don't mind either 
way and can also add the CC if you want.

bruno