Re: [PATCH v2] mt76x0: run calibration after scanning

[Stanislaw Gruszka <sgruszka@redhat.com>]

On Wed, Oct 31, 2018 at 02:11:26PM +0100, Stanislaw Gruszka wrote:
> If we are associated and scanning is performed, sw_scan_complete callback
> is done after we get back to operating channel, so we do not perform
> queue cal work. Fix this queue cal work from sw_scan_complete().
> 
> We have to restore gain in MT_BBP(AGC, 8) register after scanning, as
> it was multiple times modified by channel switch code. So queue cal work
> without  any delay and reset dev->cal.low_gain to assure calibration
> code will AGC gain value.
> 
> Note patch was not tested on mt76x2, but should work and be needed
> fix as well.
> 
> Fixes: bbd10586f0df ("mt76x0: phy: do not run calibration during channel switch")
> Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
> ---
> v1 -> v2:
> only queue cal work with 0 delay an reset dev->cal.low_gain 
> 
>  drivers/net/wireless/mediatek/mt76/mt76x02_util.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/net/wireless/mediatek/mt76/mt76x02_util.c b/drivers/net/wireless/mediatek/mt76/mt76x02_util.c
> index 9f083008dbd4..747fd2c9ec45 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt76x02_util.c
> +++ b/drivers/net/wireless/mediatek/mt76/mt76x02_util.c
> @@ -553,6 +553,12 @@ void mt76x02_sw_scan_complete(struct ieee80211_hw *hw,
>  	clear_bit(MT76_SCANNING, &dev->mt76.state);
>  	if (mt76_is_mmio(dev))
>  		tasklet_enable(&dev->pre_tbtt_tasklet);
> +
> +	if (vif->bss_conf.assoc) {
> +		/* Restore AGC gain and resume calibration after scanning. */
> +		dev->cal.low_gain = -1;
> +		ieee80211_queue_delayed_work(hw, &dev->cal_work, 0);
> +	}
>  }
>  EXPORT_SYMBOL_GPL(mt76x02_sw_scan_complete);

I think this can not be sufficient fix. Something like seems
to be needed as wall to force AGC gain write to register:

diff --git a/drivers/net/wireless/mediatek/mt76/mt76x0/phy.c b/drivers/net/wireless/mediatek/mt76/mt76x0/phy.c
index 1af2a1227924..fc4085ef3e16 100644
--- a/drivers/net/wireless/mediatek/mt76/mt76x0/phy.c
+++ b/drivers/net/wireless/mediatek/mt76/mt76x0/phy.c
@@ -833,7 +833,7 @@ mt76x0_phy_update_channel_gain(struct mt76x02_dev *dev)
        low_gain = (dev->cal.avg_rssi_all > mt76x02_get_rssi_gain_thresh(dev)) +
                   (dev->cal.avg_rssi_all > mt76x02_get_low_rssi_gain_thresh(dev));
 
-       gain_change = (dev->cal.low_gain & 2) ^ (low_gain & 2);
+       gain_change = log_gain != dev->cal.low_gain;
        dev->cal.low_gain = low_gain;

but I do not fully understand this xor logic, so I'm not sure.

Thanks
Stanislaw