ath9k: add spectral scan feature

Adds the spectral scan feature for ath9k. AR92xx and AR93xx chips
are supported for now. The spectral scan is triggered by configuring
a mode through a debugfs control file. Samples can be gathered via
another relay debugfs file.

Essentially, to try it out:

echo chanscan > /sys/kernel/debug/ieee80211/phy0/ath9k/spectral_scan_ctl
iw dev wlan0 scan
cat /sys/kernel/debug/ieee80211/phy0/ath9k/spectral_scan0 > samples
echo disable > /sys/kernel/debug/ieee80211/phy0/ath9k/spectral_scan_ctl

This feature is still experimental.

The special "chanscan" mode is used to perform spectral scan while
mac80211 is scanning for channels. To allow this,
sw_scan_start/complete() ops have been added.

The patch contains code snippets and information from Zefir Kurtisi and
information provided by Adrian Chadd and Felix Fietkau.

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Mathias Kretschmer <mathias.kretschmer@fokus.fraunhofer.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/ath9k.h

@@ -670,6 +670,23 @@ struct ath9k_vif_iter_data {
 	int nadhocs;   /* number of adhoc vifs */
 };
 
+/* enum spectral_mode:
+ *
+ * @SPECTRAL_DISABLED: spectral mode is disabled
+ * @SPECTRAL_BACKGROUND: hardware sends samples when it is not busy with
+ *	something else.
+ * @SPECTRAL_MANUAL: spectral scan is enabled, triggering for samples
+ *	is performed manually.
+ * @SPECTRAL_CHANSCAN: Like manual, but also triggered when changing channels
+ *	during a channel scan.
+ */
+enum spectral_mode {
+	SPECTRAL_DISABLED = 0,
+	SPECTRAL_BACKGROUND,
+	SPECTRAL_MANUAL,
+	SPECTRAL_CHANSCAN,
+};
+
 struct ath_softc {
 	struct ieee80211_hw *hw;
 	struct device *dev;
@@ -738,6 +755,10 @@ struct ath_softc {
 	u8 ant_tx, ant_rx;
 	struct dfs_pattern_detector *dfs_detector;
 	u32 wow_enabled;
+	/* relay(fs) channel for spectral scan */
+	struct rchan *rfs_chan_spec_scan;
+	enum spectral_mode spectral_mode;
+	int scanning;
 
 #ifdef CONFIG_PM_SLEEP
 	atomic_t wow_got_bmiss_intr;
@@ -746,6 +767,133 @@ struct ath_softc {
 #endif
 };
 
+#define SPECTRAL_SCAN_BITMASK		0x10
+/* Radar info packet format, used for DFS and spectral formats. */
+struct ath_radar_info {
+	u8 pulse_length_pri;
+	u8 pulse_length_ext;
+	u8 pulse_bw_info;
+} __packed;
+
+/* The HT20 spectral data has 4 bytes of additional information at it's end.
+ *
+ * [7:0]: all bins {max_magnitude[1:0], bitmap_weight[5:0]}
+ * [7:0]: all bins  max_magnitude[9:2]
+ * [7:0]: all bins {max_index[5:0], max_magnitude[11:10]}
+ * [3:0]: max_exp (shift amount to size max bin to 8-bit unsigned)
+ */
+struct ath_ht20_mag_info {
+	u8 all_bins[3];
+	u8 max_exp;
+} __packed;
+
+#define SPECTRAL_HT20_NUM_BINS		56
+
+/* WARNING: don't actually use this struct! MAC may vary the amount of
+ * data by -1/+2. This struct is for reference only.
+ */
+struct ath_ht20_fft_packet {
+	u8 data[SPECTRAL_HT20_NUM_BINS];
+	struct ath_ht20_mag_info mag_info;
+	struct ath_radar_info radar_info;
+} __packed;
+
+#define SPECTRAL_HT20_TOTAL_DATA_LEN	(sizeof(struct ath_ht20_fft_packet))
+
+/* Dynamic 20/40 mode:
+ *
+ * [7:0]: lower bins {max_magnitude[1:0], bitmap_weight[5:0]}
+ * [7:0]: lower bins  max_magnitude[9:2]
+ * [7:0]: lower bins {max_index[5:0], max_magnitude[11:10]}
+ * [7:0]: upper bins {max_magnitude[1:0], bitmap_weight[5:0]}
+ * [7:0]: upper bins  max_magnitude[9:2]
+ * [7:0]: upper bins {max_index[5:0], max_magnitude[11:10]}
+ * [3:0]: max_exp (shift amount to size max bin to 8-bit unsigned)
+ */
+struct ath_ht20_40_mag_info {
+	u8 lower_bins[3];
+	u8 upper_bins[3];
+	u8 max_exp;
+} __packed;
+
+#define SPECTRAL_HT20_40_NUM_BINS		128
+
+/* WARNING: don't actually use this struct! MAC may vary the amount of
+ * data. This struct is for reference only.
+ */
+struct ath_ht20_40_fft_packet {
+	u8 data[SPECTRAL_HT20_40_NUM_BINS];
+	struct ath_ht20_40_mag_info mag_info;
+	struct ath_radar_info radar_info;
+} __packed;
+
+
+#define SPECTRAL_HT20_40_TOTAL_DATA_LEN	(sizeof(struct ath_ht20_40_fft_packet))
+
+/* grabs the max magnitude from the all/upper/lower bins */
+static inline u16 spectral_max_magnitude(u8 *bins)
+{
+	return (bins[0] & 0xc0) >> 6 |
+	       (bins[1] & 0xff) << 2 |
+	       (bins[2] & 0x03) << 10;
+}
+
+/* return the max magnitude from the all/upper/lower bins */
+static inline u8 spectral_max_index(u8 *bins)
+{
+	s8 m = (bins[2] & 0xfc) >> 2;
+
+	/* TODO: this still doesn't always report the right values ... */
+	if (m > 32)
+		m |= 0xe0;
+	else
+		m &= ~0xe0;
+
+	return m + 29;
+}
+
+/* return the bitmap weight from the all/upper/lower bins */
+static inline u8 spectral_bitmap_weight(u8 *bins)
+{
+	return bins[0] & 0x3f;
+}
+
+/* FFT sample format given to userspace via debugfs.
+ *
+ * Please keep the type/length at the front position and change
+ * other fields after adding another sample type
+ *
+ * TODO: this might need rework when switching to nl80211-based
+ * interface.
+ */
+enum ath_fft_sample_type {
+	ATH_FFT_SAMPLE_HT20 = 0,
+};
+
+struct fft_sample_tlv {
+	u8 type;	/* see ath_fft_sample */
+	u16 length;
+	/* type dependent data follows */
+} __packed;
+
+struct fft_sample_ht20 {
+	struct fft_sample_tlv tlv;
+
+	u8 __alignment;
+
+	u16 freq;
+	s8 rssi;
+	s8 noise;
+
+	u16 max_magnitude;
+	u8 max_index;
+	u8 bitmap_weight;
+
+	u64 tsf;
+
+	u16 data[SPECTRAL_HT20_NUM_BINS];
+} __packed;
+
 void ath9k_tasklet(unsigned long data);
 int ath_cabq_update(struct ath_softc *);
 
@@ -768,6 +916,10 @@ void ath9k_set_hw_capab(struct ath_softc *sc, struct ieee80211_hw *hw);
 void ath9k_reload_chainmask_settings(struct ath_softc *sc);
 
 bool ath9k_uses_beacons(int type);
+void ath9k_spectral_scan_trigger(struct ieee80211_hw *hw);
+int ath9k_spectral_scan_config(struct ieee80211_hw *hw,
+			       enum spectral_mode spectral_mode);
+
 
 #ifdef CONFIG_ATH9K_PCI
 int ath_pci_init(void);