[PATCH 10/10] carl9170: phy: add periodic runtime IQ calibration

[Masi Osmani <mas-i@hotmail.de>]

Add periodic runtime I/Q calibration triggered from the existing
survey statistics work handler (carl9170_stat_work).  The AR9170
hardware performs initial IQ calibration during channel setup, but
I/Q imbalance drifts with temperature over time, degrading EVM
and increasing packet error rate.

The new carl9170_run_iq_calibration() function sets the DO_IQCAL
bit in PHY_TIMING_CTRL4 for both chains, which triggers the
hardware to re-measure I/Q imbalance and update the correction
coefficients automatically.  This is a non-blocking operation --
the hardware runs the calibration in the background without
interrupting normal traffic.

The ath9k driver performs similar periodic calibration via its
longcal timer (every 30s).  carl9170_stat_work runs at a
comparable interval, making it a natural trigger point.

Signed-off-by: Masi Osmani <mas-i@hotmail.de>
---
 drivers/net/wireless/ath/carl9170/carl9170.h |  1 +
 drivers/net/wireless/ath/carl9170/main.c     |  2 ++
 drivers/net/wireless/ath/carl9170/phy.c      | 36 ++++++++++++++++++++
 3 files changed, 39 insertions(+)

diff --git a/drivers/net/wireless/ath/carl9170/carl9170.h b/drivers/net/wireless/ath/carl9170/carl9170.h
index 2eedb2f..0175f8e 100644
--- a/drivers/net/wireless/ath/carl9170/carl9170.h
+++ b/drivers/net/wireless/ath/carl9170/carl9170.h
@@ -605,6 +605,7 @@ int carl9170_set_channel(struct ar9170 *ar, struct ieee80211_channel *channel,
 			 enum nl80211_channel_type bw);
 int carl9170_get_noisefloor(struct ar9170 *ar);
 void carl9170_update_channel_maxpower(struct ar9170 *ar);
+int carl9170_run_iq_calibration(struct ar9170 *ar);
 
 /* FW */
 int carl9170_parse_firmware(struct ar9170 *ar);
diff --git a/drivers/net/wireless/ath/carl9170/main.c b/drivers/net/wireless/ath/carl9170/main.c
index ebf9fa9..50c0922 100644
--- a/drivers/net/wireless/ath/carl9170/main.c
+++ b/drivers/net/wireless/ath/carl9170/main.c
@@ -910,6 +910,8 @@ static void carl9170_stat_work(struct work_struct *work)
 
 	mutex_lock(&ar->mutex);
 	err = carl9170_update_survey(ar, false, true);
+	if (!err)
+		carl9170_run_iq_calibration(ar);
 	mutex_unlock(&ar->mutex);
 
 	if (err)
diff --git a/drivers/net/wireless/ath/carl9170/phy.c b/drivers/net/wireless/ath/carl9170/phy.c
index c294df7..b145e9e 100644
--- a/drivers/net/wireless/ath/carl9170/phy.c
+++ b/drivers/net/wireless/ath/carl9170/phy.c
@@ -1637,6 +1637,42 @@ void carl9170_update_channel_maxpower(struct ar9170 *ar)
 	}
 }
 
+int carl9170_run_iq_calibration(struct ar9170 *ar)
+{
+	u32 val;
+	int err;
+
+	if (!ar->channel)
+		return 0;
+
+	/*
+	 * Trigger runtime IQ calibration.  The hardware measures
+	 * I/Q imbalance and updates the correction coefficients
+	 * automatically when DO_IQCAL is set.  We trigger on both
+	 * chains and re-enable the IQ correction afterwards.
+	 */
+	err = carl9170_read_reg(ar, AR9170_PHY_REG_TIMING_CTRL4(0), &val);
+	if (err)
+		return err;
+
+	val |= AR9170_PHY_TIMING_CTRL4_DO_IQCAL;
+	err = carl9170_write_reg(ar, AR9170_PHY_REG_TIMING_CTRL4(0), val);
+	if (err)
+		return err;
+
+	/* chain 2 */
+	err = carl9170_read_reg(ar, AR9170_PHY_REG_TIMING_CTRL4(2), &val);
+	if (err)
+		return err;
+
+	val |= AR9170_PHY_TIMING_CTRL4_DO_IQCAL;
+	err = carl9170_write_reg(ar, AR9170_PHY_REG_TIMING_CTRL4(2), val);
+	if (err)
+		return err;
+
+	return 0;
+}
+
 static int carl9170_set_radar_detection(struct ar9170 *ar,
 					struct ieee80211_channel *channel)
 {
-- 
2.51.0