[PATCH wireless-next 0/5] b43: N-PHY: fix calibrations on rev7+ (BCM43228)

[Luca Casati]

On a BCM43228 (14e4:4359, N-PHY rev 16, radio 2057 rev 9) b43
associates but transmits poorly: high retry counts and low rates.
Comparing mmiotraces of b43 and the proprietary wl driver
(6.30.223.271) on the same card, together with brcmsmac, turned up
several bugs in the N-PHY calibration code:

 1. The TX tone sample table was loaded as all zeros, so every
    tone-based calibration ran without a signal.
 2. TX IQ/LO calibration: inverted busy poll, reversed final copy,
    and missing rev7+ cleanup that left TX dead after a cal.
 3. RSSI calibration: wrong VCM written on rev7+, wrong distance
    formula, wrong rounding of negative offsets.
 4. 2057 RC calibration: the first run was polled before it started,
    leaving SCAP at 0 and the TX low-pass filter detuned.
 5. A missing field in the rev7 TX_PU RF override.

After these, the register writes for the cals match wl's on this card.

Patches 4 and 5 and the cleanup parts of patch 2 only affect rev7+.
Patch 1, the poll and final-copy fixes in patch 2, and the
distance/rounding fixes in patch 3 also change code that runs on older
N-PHYs (rev3+); I could only test rev 16, so testing on other N-PHY
cards would be welcome.

Tested on the BCM43228 only (2.4 GHz, 11g/HT20), on v7.0; the series
also applies to wireless-next. Throughput to the internet went from
about 5.7/4.1 to 11.1/5.2 Mbit/s down/up, with fewer TX retries. That
number is limited by the line and noisy, so take it as a rough
indication; wl reaches 21-32 Mbit/s down on the same setup, so there
is more to do (PAPD and TX power control on rev7+).

Comments and changelogs refer to wl where the fix was checked against
its register writes. If citing the proprietary driver is not
acceptable here, I am happy to reword them.

The bugs were found and the fixes drafted with the help of an AI
coding assistant (Claude Opus 5.5), working from the mmiotrace diffs
between b43 and wl and from brcmsmac. I reviewed and tested every
patch on the hardware above.

Luca Casati (5):
  b43: N-PHY: fix the TX tone sample table
  b43: N-PHY: fix TX IQ/LO calibration
  b43: N-PHY: fix rev3+ RSSI calibration
  b43: N-PHY: wait for the first 2057 RC calibration run
  b43: N-PHY: add the missing override to the rev7 TX_PU command

 drivers/net/wireless/broadcom/b43/phy_n.c | 120 +++++++++++++++++++---
 1 file changed, 106 insertions(+), 14 deletions(-)


base-commit: 028ef9c96e96197026887c0f092424679298aae8
-- 
2.43.0