Re: [PATCH wireless-next v2 2/7] wifi: rt2800: calibrate the crystal of RT3593 with the beacons

[Stanislaw Gruszka <stf_xl@wp.pl>]

Hi,

On Sun, Nov 01, 2026 at 12:51:09AM +0800, Ho Jie Feng wrote:
> 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@gmail.com>
> ---
>  drivers/net/wireless/ralink/rt2x00/rt2800.h   |   1 +
>  .../net/wireless/ralink/rt2x00/rt2800lib.c    | 101 ++++++++++++++++++
>  .../net/wireless/ralink/rt2x00/rt2800lib.h    |   4 +
>  .../net/wireless/ralink/rt2x00/rt2800usb.c    |   1 +
>  drivers/net/wireless/ralink/rt2x00/rt2x00.h   |   6 ++
>  .../net/wireless/ralink/rt2x00/rt2x00lib.h    |   2 +
>  .../net/wireless/ralink/rt2x00/rt2x00link.c   |   9 ++
>  7 files changed, 124 insertions(+)
> 
> diff --git a/drivers/net/wireless/ralink/rt2x00/rt2800.h b/drivers/net/wireless/ralink/rt2x00/rt2800.h
> index 8930589b4967d..b9f6de3a462e3 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 2e2e382b62475..e7b6edf485099 100644
> --- a/drivers/net/wireless/ralink/rt2x00/rt2800lib.c
> +++ b/drivers/net/wireless/ralink/rt2x00/rt2800lib.c
> @@ -897,6 +897,28 @@ static int rt2800_agc_to_rssi(struct rt2x00_dev *rt2x00dev, u32 rxwi_w2)
>  	return (int)max(rssi0, rssi2);
>  }
>  
> +static void rt2800_rx_freq_offset(struct queue_entry *entry,
> +				  struct rxdone_entry_desc *rxdesc)
> +{
> +	struct rt2800_drv_data *drv_data = entry->queue->rt2x00dev->drv_data;
> +	__le32 *rxwi = (__le32 *) entry->skb->data;
> +	struct ieee80211_hdr *hdr =
> +	    (void *)(entry->skb->data + entry->queue->winfo_size);
> +	u32 word;
> +
> +	if (!(rxdesc->dev_flags & RXDONE_MY_BSS) ||
> +	    (rxdesc->flags & RX_FLAG_FAILED_FCS_CRC) ||
> +	    !ieee80211_is_beacon(hdr->frame_control))
> +		return;
> +
> +	word = rt2x00_desc_read(rxwi, 3);
> +
> +	spin_lock_bh(&drv_data->bcn_lock);
> +	drv_data->bcn_freq_offset = rt2x00_get_field32(word, RXWI_W3_FOFFSET);
> +	drv_data->bcn_rate_mode = rxdesc->rate_mode;
> +	spin_unlock_bh(&drv_data->bcn_lock);
> +}
> +
>  void rt2800_process_rxwi(struct queue_entry *entry,
>  			 struct rxdone_entry_desc *rxdesc)
>  {
> @@ -935,6 +957,14 @@ 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 of the beacons is used for the frequency
> +	 * calibration.
> +	 */
> +	if (rt2x00_rt(entry->queue->rt2x00dev, RT3593))
> +		rt2800_rx_freq_offset(entry, rxdesc);
> +

I dislike fact that this is part of ->fill_rxdone() callback.
I think it would be better to add new field in rxdesc and
add flag there indicating the bcn_freq_offset is valid. 

Then add new function in rt2x00lib_rxdone_skb().

Regards
Stanislaw