From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: Date: Wed, 30 Aug 2017 08:45:37 +0200 From: Greg Kroah-Hartman To: Lukas Wunner Cc: Mathias Nyman , Mason , Felipe Balbi , linux-pci , linux-usb , Linux ARM , Bjorn Helgaas , Alan Stern Subject: Re: Possible regression between 4.9 and 4.13 Message-ID: <20170830064537.GA8856@kroah.com> References: <8ac92197-907a-282b-2165-f50d1b09bd55@free.fr> <61d34811-f17c-6faf-252f-c4c81feb9e89@free.fr> <59A3D6BF.7010400@linux.intel.com> <0b089b17-00fc-5a7c-baa3-e6141029b191@free.fr> <59A56C15.2000403@linux.intel.com> <20170829133852.GA13355@wunner.de> <20170829144725.GB22532@kroah.com> <20170829153456.GA13712@wunner.de> <20170829155138.GA32369@kroah.com> <20170830063623.GA16076@wunner.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20170830063623.GA16076@wunner.de> List-ID: On Wed, Aug 30, 2017 at 08:36:23AM +0200, Lukas Wunner wrote: > On Tue, Aug 29, 2017 at 05:51:38PM +0200, Greg Kroah-Hartman wrote: > > On Tue, Aug 29, 2017 at 05:34:56PM +0200, Lukas Wunner wrote: > > > On Tue, Aug 29, 2017 at 04:47:25PM +0200, Greg Kroah-Hartman wrote: > > > > On Tue, Aug 29, 2017 at 03:38:52PM +0200, Lukas Wunner wrote: > > > Is 0xffffffff not a valid value to be stored in and read from mmio space? > > > > For a specific register, doubtful > > Well, "doubtful" means you don't know for sure. > > It's fine to check for "all ones" as a heuristic if that's not a valid > value for the register read, however a hotplug notification is a > *definitive* indication the hardware is gone. > > I you seem to prefer forgoing a *definitive* indication for a mere > heuristic, that doesn't make sense from my point of view. I still don't know what you are arguing about here. The _driver_ knows if a specific read allows all ones as a valid return value. If it isn't, then the driver knows the device is now gone. It's that simple, don't do that type of check if all ones is a valid read. And that's not what is happening here anyway, so again, what is this discussion about? Unless there's something specific we can do here for the xhci driver, I think this thread is dead until someone determines what is going wrong with the hardware the original reporter posted about. greg k-h From mboxrd@z Thu Jan 1 00:00:00 1970 From: gregkh@linuxfoundation.org (Greg Kroah-Hartman) Date: Wed, 30 Aug 2017 08:45:37 +0200 Subject: Possible regression between 4.9 and 4.13 In-Reply-To: <20170830063623.GA16076@wunner.de> References: <8ac92197-907a-282b-2165-f50d1b09bd55@free.fr> <61d34811-f17c-6faf-252f-c4c81feb9e89@free.fr> <59A3D6BF.7010400@linux.intel.com> <0b089b17-00fc-5a7c-baa3-e6141029b191@free.fr> <59A56C15.2000403@linux.intel.com> <20170829133852.GA13355@wunner.de> <20170829144725.GB22532@kroah.com> <20170829153456.GA13712@wunner.de> <20170829155138.GA32369@kroah.com> <20170830063623.GA16076@wunner.de> Message-ID: <20170830064537.GA8856@kroah.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Aug 30, 2017 at 08:36:23AM +0200, Lukas Wunner wrote: > On Tue, Aug 29, 2017 at 05:51:38PM +0200, Greg Kroah-Hartman wrote: > > On Tue, Aug 29, 2017 at 05:34:56PM +0200, Lukas Wunner wrote: > > > On Tue, Aug 29, 2017 at 04:47:25PM +0200, Greg Kroah-Hartman wrote: > > > > On Tue, Aug 29, 2017 at 03:38:52PM +0200, Lukas Wunner wrote: > > > Is 0xffffffff not a valid value to be stored in and read from mmio space? > > > > For a specific register, doubtful > > Well, "doubtful" means you don't know for sure. > > It's fine to check for "all ones" as a heuristic if that's not a valid > value for the register read, however a hotplug notification is a > *definitive* indication the hardware is gone. > > I you seem to prefer forgoing a *definitive* indication for a mere > heuristic, that doesn't make sense from my point of view. I still don't know what you are arguing about here. The _driver_ knows if a specific read allows all ones as a valid return value. If it isn't, then the driver knows the device is now gone. It's that simple, don't do that type of check if all ones is a valid read. And that's not what is happening here anyway, so again, what is this discussion about? Unless there's something specific we can do here for the xhci driver, I think this thread is dead until someone determines what is going wrong with the hardware the original reporter posted about. greg k-h