[PATCH 3/3] ath9k: add noise floor override option

[Simon Wunderlich]

On Friday, March 17, 2017 9:48:07 AM CET Janusz Dziedzic wrote:
> On 16 March 2017 at 16:13, Simon Wunderlich <sw at simonwunderlich.de> wrote:
> > Introduce a debugfs option to manually override the noise floor,
> > ignoring the automatically tuned noise floor of the driver/hw.
> > 
> > In my tests with a AR9580 based module and a tx99 5 MHz interferer,
> > I could tune the noisefloor to -95 dBm or above to allow communication
> > again. The automatic noise floor calibration sometimes could adapt to
> > the situation as well, but not reliably and permanently.
> > 
> > I would consider this "feature" experimental and interesting for people
> > debugging the noise floor calibration or other effects of the hardware.
> > 
> > Signed-off-by: Simon Wunderlich <sw at simonwunderlich.de>
> > Signed-off-by: Mathias Kretschmer <mathias.kretschmer at fit.fraunhofer.de>
> > ---
> > 
> >  drivers/net/wireless/ath/ath9k/calib.c |  5 ++-
> >  drivers/net/wireless/ath/ath9k/debug.c | 62
> >  ++++++++++++++++++++++++++++++++++ drivers/net/wireless/ath/ath9k/hw.h  
> >   |  1 +
> >  3 files changed, 67 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/wireless/ath/ath9k/calib.c
> > b/drivers/net/wireless/ath/ath9k/calib.c index 0f71146b781d..13ab6bc46775
> > 100644
> > --- a/drivers/net/wireless/ath/ath9k/calib.c
> > +++ b/drivers/net/wireless/ath/ath9k/calib.c
> > @@ -254,7 +254,9 @@ int ath9k_hw_loadnf(struct ath_hw *ah, struct
> > ath9k_channel *chan)> 
> >                         if ((i >= AR5416_MAX_CHAINS) &&
> >                         !IS_CHAN_HT40(chan))
> >                         
> >                                 continue;
> > 
> > -                       if (h)
> > +                       if (ah->nf_override)
> > +                               nfval = ah->nf_override;
> > +                       else if (h)
> > 
> >                                 nfval = h[i].privNF;
> >                         
> >                         else
> >                         
> >                                 nfval = default_nf;
> > 
> > @@ -348,6 +350,7 @@ int ath9k_hw_loadnf(struct ath_hw *ah, struct
> > ath9k_channel *chan)> 
> >         return 0;
> >  
> >  }
> > 
> > +EXPORT_SYMBOL(ath9k_hw_loadnf);
> > 
> >  static void ath9k_hw_nf_sanitize(struct ath_hw *ah, s16 *nf)
> > 
> > diff --git a/drivers/net/wireless/ath/ath9k/debug.c
> > b/drivers/net/wireless/ath/ath9k/debug.c index 43930c336987..2e64977a8ab6
> > 100644
> > --- a/drivers/net/wireless/ath/ath9k/debug.c
> > +++ b/drivers/net/wireless/ath/ath9k/debug.c
> > @@ -1191,6 +1191,65 @@ static const struct file_operations fops_tpc = {
> > 
> >         .llseek = default_llseek,
> >  
> >  };
> > 
> > +static ssize_t read_file_nf_override(struct file *file,
> > +                                    char __user *user_buf,
> > +                                    size_t count, loff_t *ppos)
> > +{
> > +       struct ath_softc *sc = file->private_data;
> > +       struct ath_hw *ah = sc->sc_ah;
> > +       char buf[32];
> > +       unsigned int len;
> > +
> > +       if (ah->nf_override == 0)
> > +               len = sprintf(buf, "off\n");
> > +       else
> > +               len = sprintf(buf, "%d\n", ah->nf_override);
> > +
> > +       return simple_read_from_buffer(user_buf, count, ppos, buf, len);
> > +}
> > +
> > +static ssize_t write_file_nf_override(struct file *file,
> > +                                     const char __user *user_buf,
> > +                                     size_t count, loff_t *ppos)
> > +{
> > +       struct ath_softc *sc = file->private_data;
> > +       struct ath_hw *ah = sc->sc_ah;
> > +       long val;
> > +       char buf[32];
> > +       ssize_t len;
> > +
> > +       len = min(count, sizeof(buf) - 1);
> > +       if (copy_from_user(buf, user_buf, len))
> > +               return -EFAULT;
> > +
> > +       buf[len] = '\0';
> > +       if (strncmp("off", buf, 3) == 0)
> > +               val = 0;
> > +       else if (kstrtol(buf, 0, &val))
> > +               return -EINVAL;
> > +
> > +       if (val > 0)
> > +               return -EINVAL;
> > +
> > +       if (val < -120)
> > +               return -EINVAL;
> > +
> > +       ah->nf_override = val;
> > +
> > +       if (ah->curchan)
> > +               ath9k_hw_loadnf(ah, ah->curchan);
> > +
> > +       return count;
> > +}
> > +
> > +static const struct file_operations fops_nf_override = {
> > +       .read = read_file_nf_override,
> > +       .write = write_file_nf_override,
> > +       .open = simple_open,
> > +       .owner = THIS_MODULE,
> > +       .llseek = default_llseek,
> > +};
> > +
> > 
> >  /* Ethtool support for get-stats */
> >  
> >  #define AMKSTR(nm) #nm "_BE", #nm "_BK", #nm "_VI", #nm "_VO"
> > 
> > @@ -1402,5 +1461,8 @@ int ath9k_init_debug(struct ath_hw *ah)
> > 
> >         debugfs_create_u16("airtime_flags", S_IRUSR | S_IWUSR,
> >         
> >                            sc->debug.debugfs_phy, &sc->airtime_flags);
> > 
> > +       debugfs_create_file("nf_override", S_IRUSR | S_IWUSR,
> > +                           sc->debug.debugfs_phy, sc, &fops_nf_override);
> > +
> 
> Why not simply:
>         debugfs_create_u32("nf_override", S_IRUSR|S_IWUSR ,
> sc->debug.debugfs_phy,
>                           &ah->nf_override);
> 
> One line patch :)

Thanks Janusz, good idea! That doesn't check the limits, which is probably not 
a big deal anyway. What bothers me more is that it doesn't update the noise 
floor immediately (ath9k_hw_loadnf()), which would be nice to have. Otherwise 
you have to wait up to ~30 seconds or so until the noise floor is updated next 
time. So I'd keep my variant for now, unless you have a good idea to fix the 
latter. :)

Cheers,
      Simon
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