From: Larry Finger Date: Sat, 05 Apr 2014 10:49:00 -0500 Subject: [PATCH][FIX 3.15] b43: N-PHY: access B43_MMIO_PSM_PHY_HDR using 16b ops In-Reply-To: <1396708524-12199-1-git-send-email-zajec5@gmail.com> References: <1396708524-12199-1-git-send-email-zajec5@gmail.com> Message-ID: <534025EC.6030600@lwfinger.net> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= , linux-wireless@vger.kernel.org, "John W. Linville" Cc: b43-dev@lists.infradead.org On 04/05/2014 09:35 AM, Rafa? Mi?ecki wrote: > Register B43_MMIO_PSM_PHY_HDR is 16 bit one, so accessing it with 32b > functions isn't safe. On my machine it causes delayed (!) CPU exception: > > Disabling lock debugging due to kernel taint > mce: [Hardware Error]: CPU 0: Machine Check Exception: 4 Bank 4: b200000000070f0f > mce: [Hardware Error]: TSC 164083803dc > mce: [Hardware Error]: PROCESSOR 2:20fc2 TIME 1396650505 SOCKET 0 APIC 0 microcode 0 > mce: [Hardware Error]: Run the above through 'mcelog --ascii' > mce: [Hardware Error]: Machine check: Processor context corrupt > Kernel panic - not syncing: Fatal machine check on current CPU > Kernel Offset: 0x0 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffff9fffffff) > > Signed-off-by: Rafa? Mi?ecki > --- > John: I think this patch it worth picking for 3.15 release. This bug > causes instability and can be triggered depending on the default state > of B43_NPHY_BANDCTL register. > It doesn't cause exception immediately, so I spent few hours tracing it. > --- I agree that this is a BUG fix that should be in 3.15, *and* in all stable versions to which it would apply. To aid John, I suggest that a better subject would be something like "b43: Fix machine check error due to improper access of B43_MMIO_PSM_PHY_HDR". That makes it more obvious that a bug is being fixed. In addition, you should add a "Cc: Stable [2.6.35+]". As I rarely run an 802.11n Broadcom device, it is unlikely that I have encountered this problem, but your evidence is convincing. Once the subject and Cc are changed, then Acked-by: Larry Finger Larry