[PATCH wireless-next v3 2/7] wifi: rt2800: calibrate the crystal of RT3593 with the beacons
From: Ho Jie Feng
Date: Thu Nov 12 2026 - 12:16:06 EST
On a Netgear WNDA4100 (RT3593), as the adapter warms up, the
frequency offset drifts enough to affect the link quality.
In certain cases it can cause the link speed to drop
to 1Mbit/s or below.
Add a frequency calibration step function to RT3593 to use
the frequency offset obtained from the beacon frames of the AP
for tuning.
Test results:
before after
TX 27.7 28.5
RX 31.6 69.7
Signed-off-by: Ho Jie Feng <hjf3108@xxxxxxxxx>
---
drivers/net/wireless/ralink/rt2x00/rt2800.h | 1 +
.../net/wireless/ralink/rt2x00/rt2800lib.c | 77 +++++++++++++++++++
.../net/wireless/ralink/rt2x00/rt2800lib.h | 1 +
.../net/wireless/ralink/rt2x00/rt2800usb.c | 1 +
drivers/net/wireless/ralink/rt2x00/rt2x00.h | 13 ++++
.../net/wireless/ralink/rt2x00/rt2x00dev.c | 24 ++++++
.../net/wireless/ralink/rt2x00/rt2x00lib.h | 2 +
.../net/wireless/ralink/rt2x00/rt2x00link.c | 10 +++
.../net/wireless/ralink/rt2x00/rt2x00queue.h | 5 ++
9 files changed, 134 insertions(+)
diff --git a/drivers/net/wireless/ralink/rt2x00/rt2800.h b/drivers/net/wireless/ralink/rt2x00/rt2800.h
index 8930589b49..b9f6de3a46 100644
--- a/drivers/net/wireless/ralink/rt2x00/rt2800.h
+++ b/drivers/net/wireless/ralink/rt2x00/rt2800.h
@@ -3163,6 +3163,7 @@ enum rt2800_eeprom_word {
*/
#define RXWI_W3_SNR0 FIELD32(0x000000ff)
#define RXWI_W3_SNR1 FIELD32(0x0000ff00)
+#define RXWI_W3_FOFFSET FIELD32(0xff000000)
/*
* Macros for converting txpower from EEPROM to mac80211 value
diff --git a/drivers/net/wireless/ralink/rt2x00/rt2800lib.c b/drivers/net/wireless/ralink/rt2x00/rt2800lib.c
index 4f7beca668..371b293bac 100644
--- a/drivers/net/wireless/ralink/rt2x00/rt2800lib.c
+++ b/drivers/net/wireless/ralink/rt2x00/rt2800lib.c
@@ -935,6 +935,16 @@ void rt2800_process_rxwi(struct queue_entry *entry,
* Convert descriptor AGC value to RSSI value.
*/
rxdesc->rssi = rt2800_agc_to_rssi(entry->queue->rt2x00dev, word);
+
+ /*
+ * The frequency offset is used for the frequency calibration.
+ */
+ if (rt2x00_rt(entry->queue->rt2x00dev, RT3593)) {
+ word = rt2x00_desc_read(rxwi, 3);
+ rxdesc->freq_offset = rt2x00_get_field32(word, RXWI_W3_FOFFSET);
+ rxdesc->dev_flags |= RXDONE_FREQ_OFFSET;
+ }
+
/*
* Remove RXWI descriptor from start of the buffer.
*/
@@ -2441,6 +2451,7 @@ static inline bool rt2800_clk_is_20mhz(struct rt2x00_dev *rt2x00dev)
}
#define FREQ_OFFSET_BOUND 0x5f
+#define FREQ_OFFSET_INVALID -128
static void rt2800_freq_cal_mode1(struct rt2x00_dev *rt2x00dev)
{
@@ -5631,6 +5642,72 @@ void rt2800_vco_calibration(struct rt2x00_dev *rt2x00dev)
}
EXPORT_SYMBOL_GPL(rt2800_vco_calibration);
+void rt2800_freq_calibration(struct rt2x00_dev *rt2x00dev)
+{
+ struct link *link = &rt2x00dev->link;
+ u8 activate_threshold, deactivate_threshold;
+ u8 freq_offset, rate_mode;
+ u16 eeprom;
+ s8 offset;
+
+ if (!rt2x00_rt(rt2x00dev, RT3593))
+ return;
+
+ if (!rt2x00dev->intf_associated) {
+ eeprom = rt2800_eeprom_read(rt2x00dev, EEPROM_FREQ);
+ rt2x00dev->freq_offset = rt2x00_get_field16(eeprom,
+ EEPROM_FREQ_OFFSET);
+ link->freq_cal_adjusting = false;
+ return;
+ }
+
+ spin_lock_bh(&link->bcn_lock);
+ offset = link->bcn_freq_offset;
+ rate_mode = link->bcn_rate_mode;
+ link->bcn_freq_offset = FREQ_OFFSET_INVALID;
+ spin_unlock_bh(&link->bcn_lock);
+
+ /* No beacons received */
+ if (offset == FREQ_OFFSET_INVALID)
+ return;
+
+ if (rate_mode == RATE_MODE_CCK) {
+ activate_threshold = 4;
+ deactivate_threshold = 2;
+ } else {
+ activate_threshold = 20;
+ deactivate_threshold = 10;
+ }
+
+ /* Hysteresis */
+ if (abs(offset) >= activate_threshold)
+ link->freq_cal_adjusting = true;
+ else if (abs(offset) <= deactivate_threshold)
+ link->freq_cal_adjusting = false;
+
+ if (!link->freq_cal_adjusting)
+ return;
+
+ freq_offset = rt2x00_get_field8(rt2x00dev->freq_offset, RFCSR17_CODE);
+ freq_offset = min_t(u8, freq_offset, FREQ_OFFSET_BOUND);
+
+ if (offset > 0) {
+ if (freq_offset > 0)
+ freq_offset--;
+ else
+ link->freq_cal_adjusting = false;
+ } else {
+ if (freq_offset < FREQ_OFFSET_BOUND)
+ freq_offset++;
+ else
+ link->freq_cal_adjusting = false;
+ }
+
+ rt2x00dev->freq_offset = freq_offset;
+ rt2800_freq_cal_mode1(rt2x00dev);
+}
+EXPORT_SYMBOL_GPL(rt2800_freq_calibration);
+
static void rt2800_config_retry_limit(struct rt2x00_dev *rt2x00dev,
struct rt2x00lib_conf *libconf)
{
diff --git a/drivers/net/wireless/ralink/rt2x00/rt2800lib.h b/drivers/net/wireless/ralink/rt2x00/rt2800lib.h
index a3c3a751f5..1e31a61e95 100644
--- a/drivers/net/wireless/ralink/rt2x00/rt2800lib.h
+++ b/drivers/net/wireless/ralink/rt2x00/rt2800lib.h
@@ -241,6 +241,7 @@ void rt2800_link_tuner(struct rt2x00_dev *rt2x00dev, struct link_qual *qual,
const u32 count);
void rt2800_gain_calibration(struct rt2x00_dev *rt2x00dev);
void rt2800_vco_calibration(struct rt2x00_dev *rt2x00dev);
+void rt2800_freq_calibration(struct rt2x00_dev *rt2x00dev);
int rt2800_enable_radio(struct rt2x00_dev *rt2x00dev);
void rt2800_disable_radio(struct rt2x00_dev *rt2x00dev);
diff --git a/drivers/net/wireless/ralink/rt2x00/rt2800usb.c b/drivers/net/wireless/ralink/rt2x00/rt2800usb.c
index 15de3db124..387c07e225 100644
--- a/drivers/net/wireless/ralink/rt2x00/rt2800usb.c
+++ b/drivers/net/wireless/ralink/rt2x00/rt2800usb.c
@@ -693,6 +693,7 @@ static const struct rt2x00lib_ops rt2800usb_rt2x00_ops = {
.link_tuner = rt2800_link_tuner,
.gain_calibration = rt2800_gain_calibration,
.vco_calibration = rt2800_vco_calibration,
+ .freq_calibration = rt2800_freq_calibration,
.watchdog = rt2800_watchdog,
.start_queue = rt2800usb_start_queue,
.kick_queue = rt2x00usb_kick_queue,
diff --git a/drivers/net/wireless/ralink/rt2x00/rt2x00.h b/drivers/net/wireless/ralink/rt2x00/rt2x00.h
index 7d313e86d3..415ff253cb 100644
--- a/drivers/net/wireless/ralink/rt2x00/rt2x00.h
+++ b/drivers/net/wireless/ralink/rt2x00/rt2x00.h
@@ -319,6 +319,18 @@ struct link {
*/
struct ewma_rssi avg_rssi;
+ /*
+ * Controls interval of frequency calibration
+ */
+ bool freq_cal_adjusting;
+
+ /*
+ * Frequency offset and rate mode of the last beacon from the AP
+ */
+ spinlock_t bcn_lock; /* protects bcn_freq_offset, bcn_rate_mode */
+ s8 bcn_freq_offset;
+ u8 bcn_rate_mode;
+
/*
* Work structure for scheduling periodic link tuning.
*/
@@ -559,6 +571,7 @@ struct rt2x00lib_ops {
struct link_qual *qual, const u32 count);
void (*gain_calibration) (struct rt2x00_dev *rt2x00dev);
void (*vco_calibration) (struct rt2x00_dev *rt2x00dev);
+ void (*freq_calibration) (struct rt2x00_dev *rt2x00dev);
/*
* Data queue handlers.
diff --git a/drivers/net/wireless/ralink/rt2x00/rt2x00dev.c b/drivers/net/wireless/ralink/rt2x00/rt2x00dev.c
index 4d94b7062f..7b23da0678 100644
--- a/drivers/net/wireless/ralink/rt2x00/rt2x00dev.c
+++ b/drivers/net/wireless/ralink/rt2x00/rt2x00dev.c
@@ -688,6 +688,25 @@ static void rt2x00lib_rxdone_check_ps(struct rt2x00_dev *rt2x00dev,
queue_work(rt2x00dev->workqueue, &rt2x00dev->sleep_work);
}
+static void rt2x00lib_rxdone_freq_offset(struct rt2x00_dev *rt2x00dev,
+ struct sk_buff *skb,
+ struct rxdone_entry_desc *rxdesc)
+{
+ struct ieee80211_hdr *hdr = (void *)skb->data;
+ struct link *link = &rt2x00dev->link;
+
+ if (!(rxdesc->dev_flags & RXDONE_FREQ_OFFSET) ||
+ !(rxdesc->dev_flags & RXDONE_MY_BSS) ||
+ (rxdesc->flags & RX_FLAG_FAILED_FCS_CRC) ||
+ !ieee80211_is_beacon(hdr->frame_control))
+ return;
+
+ spin_lock_bh(&link->bcn_lock);
+ link->bcn_freq_offset = rxdesc->freq_offset;
+ link->bcn_rate_mode = rxdesc->rate_mode;
+ spin_unlock_bh(&link->bcn_lock);
+}
+
static int rt2x00lib_rxdone_read_signal(struct rt2x00_dev *rt2x00dev,
struct rxdone_entry_desc *rxdesc)
{
@@ -825,6 +844,11 @@ void rt2x00lib_rxdone(struct queue_entry *entry, gfp_t gfp)
*/
rt2x00lib_rxdone_check_ba(rt2x00dev, entry->skb, &rxdesc);
+ /*
+ * Store frequency offset of the beacons for frequency calibration.
+ */
+ rt2x00lib_rxdone_freq_offset(rt2x00dev, entry->skb, &rxdesc);
+
/*
* Update extra components
*/
diff --git a/drivers/net/wireless/ralink/rt2x00/rt2x00lib.h b/drivers/net/wireless/ralink/rt2x00/rt2x00lib.h
index 2f1385baa7..a6f516ebdb 100644
--- a/drivers/net/wireless/ralink/rt2x00/rt2x00lib.h
+++ b/drivers/net/wireless/ralink/rt2x00/rt2x00lib.h
@@ -22,6 +22,8 @@
#define LINK_TUNE_INTERVAL round_jiffies_relative(LINK_TUNE_SECONDS * HZ)
#define AGC_SECONDS 4
#define VCO_SECONDS 10
+#define FREQ_SECONDS 10
+#define FREQ_ADJUST_SECONDS 1
/*
* rt2x00_rate: Per rate device information
diff --git a/drivers/net/wireless/ralink/rt2x00/rt2x00link.c b/drivers/net/wireless/ralink/rt2x00/rt2x00link.c
index fb23d409fb..d44a55b14f 100644
--- a/drivers/net/wireless/ralink/rt2x00/rt2x00link.c
+++ b/drivers/net/wireless/ralink/rt2x00/rt2x00link.c
@@ -343,6 +343,7 @@ static void rt2x00link_tuner(struct work_struct *work)
struct rt2x00_dev *rt2x00dev =
container_of(work, struct rt2x00_dev, link.work.work);
struct link *link = &rt2x00dev->link;
+ unsigned int freq_interval;
/*
* When the radio is shutting down we should
@@ -362,6 +363,14 @@ static void rt2x00link_tuner(struct work_struct *work)
(link->count % (AGC_SECONDS / LINK_TUNE_SECONDS)) == 0)
rt2x00dev->ops->lib->gain_calibration(rt2x00dev);
+ freq_interval = link->freq_cal_adjusting ?
+ FREQ_ADJUST_SECONDS : FREQ_SECONDS;
+
+ /* VCO calibration should be done after frequency calibration */
+ if (rt2x00dev->ops->lib->freq_calibration &&
+ (link->count % (freq_interval / LINK_TUNE_SECONDS)) == 0)
+ rt2x00dev->ops->lib->freq_calibration(rt2x00dev);
+
if (rt2x00dev->ops->lib->vco_calibration &&
rt2x00_has_cap_vco_recalibration(rt2x00dev) &&
(link->count % (VCO_SECONDS / LINK_TUNE_SECONDS)) == 0)
@@ -422,6 +431,7 @@ void rt2x00link_register(struct rt2x00_dev *rt2x00dev)
INIT_DELAYED_WORK(&link->work, rt2x00link_tuner);
INIT_DELAYED_WORK(&link->watchdog_work, rt2x00link_watchdog);
+ spin_lock_init(&link->bcn_lock);
if (link->watchdog_interval == 0)
link->watchdog_interval = WATCHDOG_INTERVAL;
diff --git a/drivers/net/wireless/ralink/rt2x00/rt2x00queue.h b/drivers/net/wireless/ralink/rt2x00/rt2x00queue.h
index 23739dd0bc..4caf9261a5 100644
--- a/drivers/net/wireless/ralink/rt2x00/rt2x00queue.h
+++ b/drivers/net/wireless/ralink/rt2x00/rt2x00queue.h
@@ -129,6 +129,7 @@ static inline struct skb_frame_desc* get_skb_frame_desc(struct sk_buff *skb)
* @RXDONE_CRYPTO_IV: Driver provided IV/EIV data.
* @RXDONE_CRYPTO_ICV: Driver provided ICV data.
* @RXDONE_L2PAD: 802.11 payload has been padded to 4-byte boundary.
+ * @RXDONE_FREQ_OFFSET: Driver provided the frequency offset.
*/
enum rxdone_entry_desc_flags {
RXDONE_SIGNAL_PLCP = BIT(0),
@@ -138,6 +139,7 @@ enum rxdone_entry_desc_flags {
RXDONE_CRYPTO_IV = BIT(4),
RXDONE_CRYPTO_ICV = BIT(5),
RXDONE_L2PAD = BIT(6),
+ RXDONE_FREQ_OFFSET = BIT(7),
};
/**
@@ -164,6 +166,7 @@ enum rxdone_entry_desc_flags {
* @cipher_status: Decryption status.
* @iv: IV/EIV data used during decryption.
* @icv: ICV data used during decryption.
+ * @freq_offset: Frequency offset of the received frame.
*/
struct rxdone_entry_desc {
u64 timestamp;
@@ -181,6 +184,8 @@ struct rxdone_entry_desc {
__le32 iv[2];
__le32 icv;
+
+ s8 freq_offset;
};
/**
--
2.53.0