[PATCH wireless-next v2 0/5] b43: N-PHY: fix calibrations on rev7+ (BCM43228)

[Luca Casati <luk00casati@gmail.com>]

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: every delay was about twice wl's, so the
    first run was stopped while it was running and SCAP read 0
    instead of 8, detuning the TX low-pass filter.
 5. A missing field in the rev7 TX_PU RF override.

The traces, and excerpts of the operations behind each patch next to
the same operations from b43, are at:

  https://github.com/Luca00casati/b43patch/blob/755c2d8/traces/README.md

Each changelog links its excerpts.

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. With v1, 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+).

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.

Changes in v2:
- Dropped the comments the patches added.
- Patch 2: the changelog said the coefficients match wl's; they are
  close, not equal.
- Patch 4: replaced. v1 waited for the first RC cal run and explained
  it wrongly: wl stops that run right away too, just sooner. v2 uses
  wl's delays throughout the cal instead.
- Linked the mmiotrace excerpts from each changelog.

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: use wl's delays in the 2057 RC calibration
  b43: N-PHY: add the missing override to the rev7 TX_PU command

 drivers/net/wireless/broadcom/b43/phy_n.c | 115 +++++++++++++++++-----
 1 file changed, 90 insertions(+), 25 deletions(-)


base-commit: 028ef9c96e96197026887c0f092424679298aae8
-- 
2.43.0