mac80211: ath10k: adjust tx power reduction for US regulatory domain

FCC allows maximum antenna gain of 6 dBi. 15.247(b)(4):

> (4) The conducted output power limit
> specified in paragraph (b) of this section
> is based on the use of antennas
> with directional gains that do not exceed
> 6 dBi. Except as shown in paragraph
> (c) of this section, if transmitting
> antennas of directional gain greater
> than 6 dBi are used, the conducted
> output power from the intentional radiator
> shall be reduced below the stated
> values in paragraphs (b)(1), (b)(2),
> and (b)(3) of this section, as appropriate,
> by the amount in dB that the
> directional gain of the antenna exceeds
> 6 dBi.

https://www.gpo.gov/fdsys/pkg/CFR-2013-title47-vol1/pdf/CFR-2013-title47-vol1-sec15-247.pdf

Signed-off-by: Sven Eckelmann <sven@narfation.org>

1 files changed, 101 insertions, 0 deletions

diff --git a/package/kernel/mac80211/patches/ath/981-ath10k-adjust-tx-power-reduction-for-US-regulatory-d.patch b/package/kernel/mac80211/patches/ath/981-ath10k-adjust-tx-power-reduction-for-US-regulatory-d.patch
new file mode 100644
index 0000000000..07247a0577
--- /dev/null
+++ b/package/kernel/mac80211/patches/ath/981-ath10k-adjust-tx-power-reduction-for-US-regulatory-d.patch
@@ -0,0 +1,101 @@
+From: Sven Eckelmann <seckelmann@datto.com>
+Date: Wed, 28 Nov 2018 16:16:27 +0100
+Subject: ath10k: adjust tx power reduction for US regulatory domain
+
+FCC allows maximum antenna gain of 6 dBi. 15.247(b)(4):
+
+> (4) The conducted output power limit
+> specified in paragraph (b) of this section
+> is based on the use of antennas
+> with directional gains that do not exceed
+> 6 dBi. Except as shown in paragraph
+> (c) of this section, if transmitting
+> antennas of directional gain greater
+> than 6 dBi are used, the conducted
+> output power from the intentional radiator
+> shall be reduced below the stated
+> values in paragraphs (b)(1), (b)(2),
+> and (b)(3) of this section, as appropriate,
+> by the amount in dB that the
+> directional gain of the antenna exceeds
+> 6 dBi.
+
+https://www.gpo.gov/fdsys/pkg/CFR-2013-title47-vol1/pdf/CFR-2013-title47-vol1-sec15-247.pdf
+
+Signed-off-by: Sven Eckelmann <seckelmann@datto.com>
+
+Forwarded: no
+
+--- a/drivers/net/wireless/ath/ath10k/mac.c
++++ b/drivers/net/wireless/ath/ath10k/mac.c
+@@ -988,6 +988,40 @@ static inline int ath10k_vdev_setup_sync
+ 	return 0;
+ }
+ 
++static u32 ath10k_get_max_antenna_gain(struct ath10k *ar,
++				       u32 ch_max_antenna_gain)
++{
++	u32 max_antenna_gain;
++
++	if (ar->dfs_detector && ar->dfs_detector->region == NL80211_DFS_FCC) {
++		/* FCC allows maximum antenna gain of 6 dBi. 15.247(b)(4):
++		 *
++		 * > (4) The conducted output power limit
++		 * > specified in paragraph (b) of this section
++		 * > is based on the use of antennas
++		 * > with directional gains that do not exceed
++		 * > 6 dBi. Except as shown in paragraph
++		 * > (c) of this section, if transmitting
++		 * > antennas of directional gain greater
++		 * > than 6 dBi are used, the conducted
++		 * > output power from the intentional radiator
++		 * > shall be reduced below the stated
++		 * > values in paragraphs (b)(1), (b)(2),
++		 * > and (b)(3) of this section, as appropriate,
++		 * > by the amount in dB that the
++		 * > directional gain of the antenna exceeds
++		 * > 6 dBi.
++		 *
++		 * https://www.gpo.gov/fdsys/pkg/CFR-2013-title47-vol1/pdf/CFR-2013-title47-vol1-sec15-247.pdf
++		 */
++		max_antenna_gain = 6;
++	} else {
++		max_antenna_gain = 0;
++	}
++
++	return max(ch_max_antenna_gain, max_antenna_gain);
++}
++
+ static int ath10k_monitor_vdev_start(struct ath10k *ar, int vdev_id)
+ {
+ 	struct cfg80211_chan_def *chandef = NULL;
+@@ -1020,7 +1054,8 @@ static int ath10k_monitor_vdev_start(str
+ 	arg.channel.min_power = 0;
+ 	arg.channel.max_power = channel->max_power * 2;
+ 	arg.channel.max_reg_power = channel->max_reg_power * 2;
+-	arg.channel.max_antenna_gain = channel->max_antenna_gain;
++	arg.channel.max_antenna_gain = ath10k_get_max_antenna_gain(ar,
++						channel->max_antenna_gain);
+ 
+ 	reinit_completion(&ar->vdev_setup_done);
+ 
+@@ -1462,7 +1497,8 @@ static int ath10k_vdev_start_restart(str
+ 	arg.channel.min_power = 0;
+ 	arg.channel.max_power = chandef->chan->max_power * 2;
+ 	arg.channel.max_reg_power = chandef->chan->max_reg_power * 2;
+-	arg.channel.max_antenna_gain = chandef->chan->max_antenna_gain;
++	arg.channel.max_antenna_gain = ath10k_get_max_antenna_gain(ar,
++					chandef->chan->max_antenna_gain);
+ 
+ 	if (arvif->vdev_type == WMI_VDEV_TYPE_AP) {
+ 		arg.ssid = arvif->u.ap.ssid;
+@@ -3139,7 +3175,8 @@ static int ath10k_update_channel_list(st
+ 			ch->min_power = 0;
+ 			ch->max_power = channel->max_power * 2;
+ 			ch->max_reg_power = channel->max_reg_power * 2;
+-			ch->max_antenna_gain = channel->max_antenna_gain;
++			ch->max_antenna_gain = ath10k_get_max_antenna_gain(ar,
++						channel->max_antenna_gain);
+ 			ch->reg_class_id = 0; /* FIXME */
+ 
+ 			/* FIXME: why use only legacy modes, why not any