[PATCH] drivers/net/wireless/broadcom/b43: fix transmit failure when VT is switched

[Taketo Kabe]

From: Taketo Kabe <kabe at sra-tohoku.co.jp>

Fix for b43 wireless card stopping transmission when switching VTs.

Setup:
Using BCM4306 rev.03 chip based CardBus wireless card.
IRQ is shared with yenta (cardbus bridge) and i915 (display) driver.
For firmware, installed latest but dated openfwwf 5.2
(http://netweb.ing.unibs.it/~openfwwf/)

How-to-reproduce:
Do "ssh <NetBSD-remotehost>", then "ls -lR /" to generate traffic, then
repeatedly switch VTs by Alt-F1<>Alt-F2.
Eventually (within a minute) the card stops working.
You can receive traffic but no transmission.
For unknown reason it doesn't occur when just generating traffic by
"ssh <remotehost> ls -lR /".

With CONFIG_B43_DEBUG=y kernel config, when it stops,
the debug message shows
    kernel: b43-phy1 debug: Out of order TX status report on DMA ring 1. Expected 148, but got 180
The slot offset I observed so far was always 32.

When err_out2 is not set to make error messages successive,
the debug output will be like this:
kernel: b43-phy1 debug: Out of order TX status report on DMA ring 1. Expected 116, but got 148
kernel: b43-phy1 debug: Out of order TX status report on DMA ring 1. Expected 116, but got 150
kernel: b43-phy1 debug: Out of order TX status report on DMA ring 1. Expected 116, but got 120
kernel: b43-phy1 debug: Out of order TX status report on DMA ring 1. Expected 116, but got 152
kernel: b43-phy1 debug: Out of order TX status report on DMA ring 1. Expected 116, but got 122
kernel: b43-phy1 debug: Out of order TX status report on DMA ring 1. Expected 116, but got 154
kernel: b43-phy1 debug: Out of order TX status report on DMA ring 1. Expected 116, but got 124
kernel: b43-phy1 debug: Out of order TX status report on DMA ring 1. Expected 116, but got 156
kernel: b43-phy1 debug: Out of order TX status report on DMA ring 1. Expected 116, but got 126
The TX ring alternates between 2 sequences; the ring seems
to be completely confused. Controller restart is needed.

Workaround(1):
This problem doesn't occur when using propriatory firmware
you will extract by b43-fwcutter, so it may be a bug in
openfwwf firmware, as the comment in the b43_dma_handle_txstatus() suggests.
I wasn't able to find a bug in the terse openfwwf code though.

Workaround(2):
Using "pio=1" option to not use DMA makes this problem to
not occur.

Description of the patch:
This patch will forcibly reset the controller to make it
work again. Very kludgy and doesn't look right, but
the traffic will continue to flow.

Signed-off-by: Taketo Kabe <kabe at sra-tohoku.co.jp>
---
diff -up ./drivers/net/wireless/broadcom/b43/dma.c.b43 ./drivers/net/wireless/broadcom/b43/dma.c
--- ./drivers/net/wireless/broadcom/b43/dma.c.b43	2018-05-04 15:18:12.000000000 +0900
+++ ./drivers/net/wireless/broadcom/b43/dma.c	2018-05-04 15:19:24.000000000 +0900
@@ -1524,7 +1524,9 @@ void b43_dma_handle_txstatus(struct b43_
 				b43dbg(dev->wl,
 				       "Out of order TX status report on DMA ring %d. Expected %d, but got %d\n",
 				       ring->index, firstused, slot);
-			err_out2 = 1;
+			/*err_out2 = 1;*/
+			/* Reset the controller to revive operation */
+			b43_controller_restart(dev, "Out of order TX");
 			return;
 		}
 	}

-- 
kabe