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: <20190427073200.GB30973@kroah.com> Date: Sat, 27 Apr 2019 09:32:00 +0200 To: Serge Semin Cc: Richard Leitner , Serge Semin , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org List-ID: T24gU2F0LCBBcHIgMjcsIDIwMTkgYXQgMTA6MTA6MjdBTSArMDMwMCwgU2VyZ2UgU2VtaW4gd3Jv dGU6Cj4gT24gU2F0LCBBcHIgMjcsIDIwMTkgYXQgMDk6MDA6NDJBTSArMDIwMCwgR3JlZyBLcm9h aC1IYXJ0bWFuIHdyb3RlOgo+ID4gT24gRnJpLCBBcHIgMjYsIDIwMTkgYXQgMDE6NDY6NTBQTSAr MDMwMCwgU2VyZ2UgU2VtaW4gd3JvdGU6Cj4gPiA+IFNNQnVzIHNsYXZlIGNvbmZpZ3VyYXRpb24g aXMgYWN0aXZhdGVkIGJ5IENGR19TRUxbMTowXT0weDEgcGlucwo+ID4gPiBzdGF0ZS4gVGhpcyBp cyB0aGUgbW9kZSB0aGUgaHViIGlzIHN1cHBvc2VkIHRvIGJlIHRvIGxldCB0aGlzIGRyaXZlcgo+ ID4gPiB3b3JrIGNvcnJlY3RseS4gQnV0IGEgcmFjZSBjb25kaXRpb24gbWlnaHQgaGFwcGVuIHJp Z2h0IGFmdGVyIHJlc2V0Cj4gPiA+IGlzIGNsZWFyZWQgZHVlIHRvIENGR19TRUxbMF0gcGluIGJl aW5nIG11bHRpcGxleGVkIHdpdGggU01CdXMgU0NMCj4gPiA+IGZ1bmN0aW9uLiBJbiBjYXNlIGlm IHRoZSByZXNldCBwaW4gaXMgaGFuZGxlZCBieSBhIGkyYyBHUElPIGV4cGFuZGVyLAo+ID4gPiB3 aGljaCBpcyBhbHNvIHBsYWNlZCBhdCB0aGUgc2FtZSBpMmMtYnVzIHNlZ21lbnQgYXMgdGhlIHVz YjI1MXgKPiA+ID4gU01CLWludGVyZmFjZSBjb25uZWN0ZWQgdG8sIHRoZW4gdGhlIGh1YiByZXNl dCBjbGVhcmFuY2UgbWlnaHQKPiA+ID4gY2F1c2UgdGhlIENGR19TRUxbMF0gYmVpbmcgbGF0Y2hl ZCBpbiB1bnByZWRpY3RhYmxlIHN0YXRlLiBTbwo+ID4gPiBzb21ldGltZXMgdGhlIGh1YiBjb25m aWd1cmF0aW9uIG1vZGUgbWlnaHQgYmUgMHgxIChhcyBleHBlY3RlZCksCj4gPiA+IGJ1dCBzb21l dGltZXMgYmVpbmcgMHgwLCB3aGljaCBkb2Vzbid0IGltcGx5IHRvIGhhdmUgdGhlIGh1YiBTTUJ1 cy1zbGF2ZQo+ID4gPiBpbnRlcmZhY2UgYWN0aXZhdGVkIGFuZCBjb25zZXF1ZW50bHkgY2F1c2Vz IHRoaXMgZHJpdmVyIGZhaWx1cmUuCj4gPiA+IAo+ID4gPiBJbiBvcmRlciB0byBmaXggdGhlIHBy b2JsZW0gd2UgbXVzdCBtYWtlIHN1cmUgdGhlIEdQSU8tcmVzZXQgY2hpcCBkb2Vzbid0Cj4gPiA+ IHJlc2lkZSB0aGUgc2FtZSBpMmMtYnVzIHNlZ21lbnQgYXMgdGhlIFNNQnVzLWludGVyZmFjZSBv ZiB0aGUgaHViLiBJZgo+ID4gPiBpdCBkb2Vzbid0LCB3ZSBjYW4gc2FmZWx5IGJsb2NrIHRoZSBz ZWdtZW50IGZvciB0aGUgdGltZSB0aGUgcmVzZXQgaXMKPiA+ID4gY2xlYXJlZCB0byBwcmV2ZW50 IGFueW9uZSBnZW5lcmF0aW5nIGEgdHJhZmZpYyBhdCB0aGUgaTJjLWJ1cyBTQ0wgbGFuZQo+ID4g PiBjb25uZWN0ZWQgdG8gdGhlIENGR19TRUxbMF0gcGluLiBCdXQgaWYgaXQgZG9lcywgbm90aGlu ZyB3ZSBjYW4gZG8sIHNvCj4gPiA+IGp1c3QgcmV0dXJuIGFuIGVycm9yLiBJZiB3ZSBsb2NrZWQg dGhlIGkyYy1idXMgc2VnbWVudCBhbmQgdHJpZWQgdG8KPiA+ID4gY29tbXVuaWNhdGUgd2l0aCB0 aGUgR1BJTy1leHBhbmRlciwgaXQgd291bGQgY2F1c2UgYSBkZWFkbG9jay4gSWYgd2UgZGlkbid0 Cj4gPiA+IGxvY2sgdGhlIGkyYy1idXMgc2VnbWVudCwgaXQgd291bGQgcmFuZG9tbHkgY2F1c2Ug dGhlIENGR19TRUxbMF0gYml0IGZsaXAuCj4gPiA+IAo+ID4gPiBTaWduZWQtb2ZmLWJ5OiBTZXJn ZSBTZW1pbiA8ZmFuY2VyLmxhbmNlckBnbWFpbC5jb20+Cj4gPiA+IFNpZ25lZC1vZmYtYnk6IEdy ZWcgS3JvYWgtSGFydG1hbiA8Z3JlZ2toQGxpbnV4Zm91bmRhdGlvbi5vcmc+Cj4gPiAKPiA+IEkg c2lnbmVkIG9mZiBvbiB0aGlzPyAgV2hlcmU/ICBXaGVuPwo+ID4gCj4gPiBuZXZlciBhZGQgYSBz LW8tYiBsaW5lIHRoYXQgeW91IGRpZCBub3QgY3JlYXRlLCB0aGF0IGltcGxpZXMgYSBsZWdhbAo+ ID4gYWdyZWVtZW50Lgo+ID4gCj4gCj4gQWgsIHNoaXQuIFNvcnJ5LiBJIHNob3VsZCBoYXZlIGFk ZGVkIEFja2VkLWJ5LiBUaGF0J3Mgd2hhdCBJIHdhcyBnb2luZyB0byBkbywKPiBzaW5jZSB5b3Ug YWxyZWFkeSBhZGRlZCB0aGUgZmlyc3QgdmVyc2lvbiBvZiB0aGlzIGludG8gbGludXgtbmV4dCB0 cmVlLiBCdXQKPiBhcHBhcmVudGx5IGNvcHktcGFzdGVkIGFuZCBsZWZ0IGFzIGlzLi4uCgpJZiBJ IGhhdmUgYWxyZWFkeSBhcHBsaWVkIGEgcGF0Y2gsIEkgY2FuJ3QgYXBwbHkgaXQgYWdhaW4gKG9y IGEKZGlmZmVyZW50IHZlcnNpb24uKSAgWW91IG5lZWQgdG8gc2VuZCBhIGZpeC11cCBwYXRjaCBm b3IgdGhlIHJlcG9ydGVkCmlzc3VlLCBub3QgYSB3aG9sZSBuZXcgb25lIGFzIEkgY2FuIG5vdCBn byBiYWNrIGluIHRpbWUgYW5kIHJld3JpdGUKaGlzdG9yeS4KCnRoYW5rcywKCmdyZWcgay1oCg== 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 3CCD0C43219 for ; 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Sat, 27 Apr 2019 07:32:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556350323; bh=dh5f3T4cJp3SsaYCcSL9UdFWlx3AnkR8jybNow6zaJY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Wdy5R0BELeIPD6005t7eU9cvAIAW0veU1r7IIuKdKcufUc8o6y0zuxiCXtq7S2C0W lzrOsMMfMPR6+N+IeuDIZXlHm03HgLK+eqgilU+TA1CnPR0kPMg3Eu+iYlDhrOd7Rc mepHt+UsbCymYCjF1D3FQf9mlMUKsKcL7BRR8U3g= Date: Sat, 27 Apr 2019 09:32:00 +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: <20190427073200.GB30973@kroah.com> References: <20190424144914.10580-1-fancer.lancer@gmail.com> <20190426104650.30240-1-fancer.lancer@gmail.com> <20190427070042.GD28250@kroah.com> <20190427071025.hdrm3e5abnl4yock@mobilestation> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline In-Reply-To: <20190427071025.hdrm3e5abnl4yock@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: <20190427073200.sVHC4Yd4TLSzfvIj5jzPC0sJaxijsXYFhkBK-ejt9FM@z> 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