[PATCH wireless] wifi: b43: don't read the LPF bandwidth on N-PHY rev 3-6 for TX calibration

[Rosen Penev <rosenp@gmail.com>]

b43_nphy_tx_cal_phy_setup() reads the LPF bandwidth control from the RF
sequence table on all N-PHY revisions from 3 on, but only uses it on
rev 7 and later, as brcmsmac only reads it there. On a BCM4716 with an
N-PHY rev 5 (ASUS RT-N16), the read causes a data bus error, so the
TX IQ/LO calibration oopses there.

b43 does not run that calibration on these revisions yet, as
nphy->perical is 2, so this only shows when it is called. Read the LPF
bandwidth control only where it is used. With this, the calibration
runs and returns success on the RT-N16.

Fixes: 40c68f20e63c ("b43; N-PHY: write most of the missing code for revs 7+")
Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 drivers/net/wireless/broadcom/b43/phy_n.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/broadcom/b43/phy_n.c b/drivers/net/wireless/broadcom/b43/phy_n.c
index 22359bd9db47..41a8ba8e8736 100644
--- a/drivers/net/wireless/broadcom/b43/phy_n.c
+++ b/drivers/net/wireless/broadcom/b43/phy_n.c
@@ -5108,13 +5108,16 @@ static void b43_nphy_tx_cal_phy_setup(struct b43_wldev *dev)
 		b43_phy_mask(dev, B43_NPHY_PAPD_EN0, ~0x0001);
 		b43_phy_mask(dev, B43_NPHY_PAPD_EN1, ~0x0001);
 
-		tmp = b43_nphy_read_lpf_ctl(dev, 0);
-		if (phy->rev >= 19)
+		/* The RF sequence table of older revisions is shorter */
+		if (phy->rev >= 19) {
+			tmp = b43_nphy_read_lpf_ctl(dev, 0);
 			b43_nphy_rf_ctl_override_rev19(dev, 0x80, tmp, 0, false,
 						       1);
-		else if (phy->rev >= 7)
+		} else if (phy->rev >= 7) {
+			tmp = b43_nphy_read_lpf_ctl(dev, 0);
 			b43_nphy_rf_ctl_override_rev7(dev, 0x80, tmp, 0, false,
 						      1);
+		}
 
 		if (nphy->use_int_tx_iq_lo_cal && true /* FIXME */) {
 			if (phy->rev >= 19) {
-- 
2.56.0