Messages in this thread | | | Subject | Re: [BISECTED REGRESSION] b43legacy broken on G4 PowerBook | From | Larry Finger <> | Date | Wed, 5 Jun 2019 22:06:18 -0500 |
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On 6/5/19 5:50 PM, Aaro Koskinen wrote: > Hi, > > When upgrading from v5.0 -> v5.1 on G4 PowerBook, I noticed WLAN does > not work anymore: > > [ 42.004303] b43legacy-phy0: Loading firmware version 0x127, patch level 14 (2005-04-18 02:36:27) > [ 42.184837] b43legacy-phy0 debug: Chip initialized > [ 42.184873] b43legacy-phy0 ERROR: The machine/kernel does not support the required 30-bit DMA mask > > The same happens with the current mainline. > > Bisected to: > > commit 65a21b71f948406201e4f62e41f06513350ca390 > Author: Christoph Hellwig <hch@lst.de> > Date: Wed Feb 13 08:01:26 2019 +0100 > > powerpc/dma: remove dma_nommu_dma_supported > > This function is largely identical to the generic version used > everywhere else. Replace it with the generic version. > > Signed-off-by: Christoph Hellwig <hch@lst.de> > Tested-by: Christian Zigotzky <chzigotzky@xenosoft.de> > Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Aaro,
First of all, you have my sympathy for the laborious bisection on a PowerBook G4. I have done several myself. Thank you.
I confirm your results.
The ppc code has a maximum DMA size of 31 bits, thus a 32-bit request will fail. Why the 30-bit fallback fails in b43legacy fails while it works in b43 is a mystery.
Although dma_nommu_dma_supported() may be "largely identical" to dma_direct_supported(), they obviously differ. Routine dma_nommu_dma_supported() returns 1 for 32-bit systems, but I do not know what dma_direct_supported() returns.
I am trying to find a patch.
Larry
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