From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Subject: [v2] usb: usb251xb: Lock i2c-bus segment the hub resides From: Greg Kroah-Hartman Message-Id: <20190427075323.GA31478@kroah.com> Date: Sat, 27 Apr 2019 09:53:23 +0200 To: Serge Semin Cc: Richard Leitner , Serge Semin , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org List-ID: T24gU2F0LCBBcHIgMjcsIDIwMTkgYXQgMTA6Mzk6NDFBTSArMDMwMCwgU2VyZ2UgU2VtaW4gd3Jv dGU6Cj4gT24gU2F0LCBBcHIgMjcsIDIwMTkgYXQgMDk6MzI6MDBBTSArMDIwMCwgR3JlZyBLcm9h aC1IYXJ0bWFuIHdyb3RlOgo+ID4gT24gU2F0LCBBcHIgMjcsIDIwMTkgYXQgMTA6MTA6MjdBTSAr MDMwMCwgU2VyZ2UgU2VtaW4gd3JvdGU6Cj4gPiA+IE9uIFNhdCwgQXByIDI3LCAyMDE5IGF0IDA5 OjAwOjQyQU0gKzAyMDAsIEdyZWcgS3JvYWgtSGFydG1hbiB3cm90ZToKPiA+ID4gPiBPbiBGcmks IEFwciAyNiwgMjAxOSBhdCAwMTo0Njo1MFBNICswMzAwLCBTZXJnZSBTZW1pbiB3cm90ZToKPiA+ ID4gPiA+IFNNQnVzIHNsYXZlIGNvbmZpZ3VyYXRpb24gaXMgYWN0aXZhdGVkIGJ5IENGR19TRUxb MTowXT0weDEgcGlucwo+ID4gPiA+ID4gc3RhdGUuIFRoaXMgaXMgdGhlIG1vZGUgdGhlIGh1YiBp cyBzdXBwb3NlZCB0byBiZSB0byBsZXQgdGhpcyBkcml2ZXIKPiA+ID4gPiA+IHdvcmsgY29ycmVj dGx5LiBCdXQgYSByYWNlIGNvbmRpdGlvbiBtaWdodCBoYXBwZW4gcmlnaHQgYWZ0ZXIgcmVzZXQK PiA+ID4gPiA+IGlzIGNsZWFyZWQgZHVlIHRvIENGR19TRUxbMF0gcGluIGJlaW5nIG11bHRpcGxl eGVkIHdpdGggU01CdXMgU0NMCj4gPiA+ID4gPiBmdW5jdGlvbi4gSW4gY2FzZSBpZiB0aGUgcmVz ZXQgcGluIGlzIGhhbmRsZWQgYnkgYSBpMmMgR1BJTyBleHBhbmRlciwKPiA+ID4gPiA+IHdoaWNo IGlzIGFsc28gcGxhY2VkIGF0IHRoZSBzYW1lIGkyYy1idXMgc2VnbWVudCBhcyB0aGUgdXNiMjUx eAo+ID4gPiA+ID4gU01CLWludGVyZmFjZSBjb25uZWN0ZWQgdG8sIHRoZW4gdGhlIGh1YiByZXNl dCBjbGVhcmFuY2UgbWlnaHQKPiA+ID4gPiA+IGNhdXNlIHRoZSBDRkdfU0VMWzBdIGJlaW5nIGxh dGNoZWQgaW4gdW5wcmVkaWN0YWJsZSBzdGF0ZS4gU28KPiA+ID4gPiA+IHNvbWV0aW1lcyB0aGUg aHViIGNvbmZpZ3VyYXRpb24gbW9kZSBtaWdodCBiZSAweDEgKGFzIGV4cGVjdGVkKSwKPiA+ID4g PiA+IGJ1dCBzb21ldGltZXMgYmVpbmcgMHgwLCB3aGljaCBkb2Vzbid0IGltcGx5IHRvIGhhdmUg dGhlIGh1YiBTTUJ1cy1zbGF2ZQo+ID4gPiA+ID4gaW50ZXJmYWNlIGFjdGl2YXRlZCBhbmQgY29u c2VxdWVudGx5IGNhdXNlcyB0aGlzIGRyaXZlciBmYWlsdXJlLgo+ID4gPiA+ID4gCj4gPiA+ID4g PiBJbiBvcmRlciB0byBmaXggdGhlIHByb2JsZW0gd2UgbXVzdCBtYWtlIHN1cmUgdGhlIEdQSU8t cmVzZXQgY2hpcCBkb2Vzbid0Cj4gPiA+ID4gPiByZXNpZGUgdGhlIHNhbWUgaTJjLWJ1cyBzZWdt ZW50IGFzIHRoZSBTTUJ1cy1pbnRlcmZhY2Ugb2YgdGhlIGh1Yi4gSWYKPiA+ID4gPiA+IGl0IGRv ZXNuJ3QsIHdlIGNhbiBzYWZlbHkgYmxvY2sgdGhlIHNlZ21lbnQgZm9yIHRoZSB0aW1lIHRoZSBy ZXNldCBpcwo+ID4gPiA+ID4gY2xlYXJlZCB0byBwcmV2ZW50IGFueW9uZSBnZW5lcmF0aW5nIGEg dHJhZmZpYyBhdCB0aGUgaTJjLWJ1cyBTQ0wgbGFuZQo+ID4gPiA+ID4gY29ubmVjdGVkIHRvIHRo ZSBDRkdfU0VMWzBdIHBpbi4gQnV0IGlmIGl0IGRvZXMsIG5vdGhpbmcgd2UgY2FuIGRvLCBzbwo+ ID4gPiA+ID4ganVzdCByZXR1cm4gYW4gZXJyb3IuIElmIHdlIGxvY2tlZCB0aGUgaTJjLWJ1cyBz ZWdtZW50IGFuZCB0cmllZCB0bwo+ID4gPiA+ID4gY29tbXVuaWNhdGUgd2l0aCB0aGUgR1BJTy1l eHBhbmRlciwgaXQgd291bGQgY2F1c2UgYSBkZWFkbG9jay4gSWYgd2UgZGlkbid0Cj4gPiA+ID4g PiBsb2NrIHRoZSBpMmMtYnVzIHNlZ21lbnQsIGl0IHdvdWxkIHJhbmRvbWx5IGNhdXNlIHRoZSBD RkdfU0VMWzBdIGJpdCBmbGlwLgo+ID4gPiA+ID4gCj4gPiA+ID4gPiBTaWduZWQtb2ZmLWJ5OiBT ZXJnZSBTZW1pbiA8ZmFuY2VyLmxhbmNlckBnbWFpbC5jb20+Cj4gPiA+ID4gPiBTaWduZWQtb2Zm LWJ5OiBHcmVnIEtyb2FoLUhhcnRtYW4gPGdyZWdraEBsaW51eGZvdW5kYXRpb24ub3JnPgo+ID4g PiA+IAo+ID4gPiA+IEkgc2lnbmVkIG9mZiBvbiB0aGlzPyAgV2hlcmU/ICBXaGVuPwo+ID4gPiA+ IAo+ID4gPiA+IG5ldmVyIGFkZCBhIHMtby1iIGxpbmUgdGhhdCB5b3UgZGlkIG5vdCBjcmVhdGUs IHRoYXQgaW1wbGllcyBhIGxlZ2FsCj4gPiA+ID4gYWdyZWVtZW50Lgo+ID4gPiA+IAo+ID4gPiAK PiA+ID4gQWgsIHNoaXQuIFNvcnJ5LiBJIHNob3VsZCBoYXZlIGFkZGVkIEFja2VkLWJ5LiBUaGF0 J3Mgd2hhdCBJIHdhcyBnb2luZyB0byBkbywKPiA+ID4gc2luY2UgeW91IGFscmVhZHkgYWRkZWQg dGhlIGZpcnN0IHZlcnNpb24gb2YgdGhpcyBpbnRvIGxpbnV4LW5leHQgdHJlZS4gQnV0Cj4gPiA+ IGFwcGFyZW50bHkgY29weS1wYXN0ZWQgYW5kIGxlZnQgYXMgaXMuLi4KPiA+IAo+ID4gSWYgSSBo YXZlIGFscmVhZHkgYXBwbGllZCBhIHBhdGNoLCBJIGNhbid0IGFwcGx5IGl0IGFnYWluIChvciBh Cj4gPiBkaWZmZXJlbnQgdmVyc2lvbi4pICBZb3UgbmVlZCB0byBzZW5kIGEgZml4LXVwIHBhdGNo IGZvciB0aGUgcmVwb3J0ZWQKPiA+IGlzc3VlLCBub3QgYSB3aG9sZSBuZXcgb25lIGFzIEkgY2Fu IG5vdCBnbyBiYWNrIGluIHRpbWUgYW5kIHJld3JpdGUKPiA+IGhpc3RvcnkuCj4gPiAKPiA+IHRo YW5rcywKPiA+IAo+ID4gZ3JlZyBrLWgKPiAKPiBPay4gU2hvdWxkIEkgc2VuZCBpdCBpbiByZXBs eSB0byB0aGlzIHBhdGNoIG9yIGFzIGEgY29tcGxldGVseSBzZXBhcmF0ZSBvbmU/CgpBIHNlcGFy YXRlIG9uZS4K From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS, T_DKIMWL_WL_HIGH,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CB2D5C43219 for ; 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Sat, 27 Apr 2019 07:53:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556351606; bh=F1/SyfQad7ViMMBtSYoO0HmqZF/1FHTyMgOydajuTts=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=jjmOovF3AsFUIUnOBpRiVGWYNX9ua5t6iHwnFH+5C8wi0hZ9tMIOPVWbAC6yI3TzM PQL8DAotzEF4D3V0hlkvT/tZpYs5aAwi9yh0Z7UNalaEwWhV2IJ9wqIn4nZ/fYlOSg CdTxo7cIDWteMK9yKfvJ0uLYFCBbfBNcIm1Qbeig= Date: Sat, 27 Apr 2019 09:53:23 +0200 From: Greg Kroah-Hartman To: Serge Semin Cc: Richard Leitner , Serge Semin , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] usb: usb251xb: Lock i2c-bus segment the hub resides Message-ID: <20190427075323.GA31478@kroah.com> References: <20190424144914.10580-1-fancer.lancer@gmail.com> <20190426104650.30240-1-fancer.lancer@gmail.com> <20190427070042.GD28250@kroah.com> <20190427071025.hdrm3e5abnl4yock@mobilestation> <20190427073200.GB30973@kroah.com> <20190427073940.6yzhklfus4qd6ver@mobilestation> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline In-Reply-To: <20190427073940.6yzhklfus4qd6ver@mobilestation> User-Agent: Mutt/1.11.4 (2019-03-13) Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Message-ID: <20190427075323.St2-N1MFGBB0NZACXYxu03fRSyEjLiZ4F-j6S0lQRD4@z> On Sat, Apr 27, 2019 at 10:39:41AM +0300, Serge Semin wrote: > On Sat, Apr 27, 2019 at 09:32:00AM +0200, Greg Kroah-Hartman wrote: > > On Sat, Apr 27, 2019 at 10:10:27AM +0300, Serge Semin wrote: > > > On Sat, Apr 27, 2019 at 09:00:42AM +0200, Greg Kroah-Hartman wrote: > > > > On Fri, Apr 26, 2019 at 01:46:50PM +0300, Serge Semin wrote: > > > > > SMBus slave configuration is activated by CFG_SEL[1:0]=0x1 pins > > > > > state. This is the mode the hub is supposed to be to let this driver > > > > > work correctly. But a race condition might happen right after reset > > > > > is cleared due to CFG_SEL[0] pin being multiplexed with SMBus SCL > > > > > function. In case if the reset pin is handled by a i2c GPIO expander, > > > > > which is also placed at the same i2c-bus segment as the usb251x > > > > > SMB-interface connected to, then the hub reset clearance might > > > > > cause the CFG_SEL[0] being latched in unpredictable state. So > > > > > sometimes the hub configuration mode might be 0x1 (as expected), > > > > > but sometimes being 0x0, which doesn't imply to have the hub SMBus-slave > > > > > interface activated and consequently causes this driver failure. > > > > > > > > > > In order to fix the problem we must make sure the GPIO-reset chip doesn't > > > > > reside the same i2c-bus segment as the SMBus-interface of the hub. If > > > > > it doesn't, we can safely block the segment for the time the reset is > > > > > cleared to prevent anyone generating a traffic at the i2c-bus SCL lane > > > > > connected to the CFG_SEL[0] pin. But if it does, nothing we can do, so > > > > > just return an error. If we locked the i2c-bus segment and tried to > > > > > communicate with the GPIO-expander, it would cause a deadlock. If we didn't > > > > > lock the i2c-bus segment, it would randomly cause the CFG_SEL[0] bit flip. > > > > > > > > > > Signed-off-by: Serge Semin > > > > > Signed-off-by: Greg Kroah-Hartman > > > > > > > > I signed off on this? Where? When? > > > > > > > > never add a s-o-b line that you did not create, that implies a legal > > > > agreement. > > > > > > > > > > Ah, shit. Sorry. I should have added Acked-by. That's what I was going to do, > > > since you already added the first version of this into linux-next tree. But > > > apparently copy-pasted and left as is... > > > > If I have already applied a patch, I can't apply it again (or a > > different version.) You need to send a fix-up patch for the reported > > issue, not a whole new one as I can not go back in time and rewrite > > history. > > > > thanks, > > > > greg k-h > > Ok. Should I send it in reply to this patch or as a completely separate one? A separate one.