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[24.31.245.230]) by smtp.gmail.com with ESMTPSA id y4sm245567oiy.56.2019.06.05.20.06.19 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Wed, 05 Jun 2019 20:06:19 -0700 (PDT) Subject: Re: [BISECTED REGRESSION] b43legacy broken on G4 PowerBook To: Aaro Koskinen , Christoph Hellwig , Christian Zigotzky , Michael Ellerman Cc: linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org, linuxppc-dev@lists.ozlabs.org References: <20190605225059.GA9953@darkstar.musicnaut.iki.fi> From: Larry Finger Message-ID: <35b3f09b-b371-e2cc-4436-120c67e2f1fb@lwfinger.net> Date: Wed, 5 Jun 2019 22:06:18 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190605225059.GA9953@darkstar.musicnaut.iki.fi> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org 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 > 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 > Tested-by: Christian Zigotzky > Signed-off-by: Michael Ellerman 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