linux-kernel - Re: [PATCH V9] i2c: i2c-qcom-geni: Add shutdown callback for i2c

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 7 May 2021 13:09:21 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     rojay@...eaurora.org
Cc:     wsa@...nel.org, dianders@...omium.org,
        saiprakash.ranjan@...eaurora.org, gregkh@...uxfoundation.org,
        mka@...omium.org, skananth@...eaurora.org,
        msavaliy@....qualcomm.com, skakit@...eaurora.org,
        rnayak@...eaurora.org, agross@...nel.org,
        bjorn.andersson@...aro.org, linux-arm-msm@...r.kernel.org,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        sumit.semwal@...aro.org, linux-media@...r.kernel.org
Subject: Re: [PATCH V9] i2c: i2c-qcom-geni: Add shutdown callback for i2c

Quoting rojay@...eaurora.org (2021-05-07 03:07:42)
> On 2021-05-05 07:08, Stephen Boyd wrote:
> > Quoting Roja Rani Yarubandi (2021-04-20 04:13:55)
>
> > In fact, where is that code? I'd expect to see i2c_del_adapter() in
> > here
> > so we know the adapter can't accept transfers anymore. Maybe
> > i2c_del_adapter() could be called, and then there's nothing to do after
> > that? This whole patch is trying to rip the adapter out from under the
> > i2c core framework, when we should take the opposite approach and
> > remove
> > it from the core framework so that it can't transfer anything anymore
> > and thus the IOMMU can remove the mapping.
> >
>
> IIUC about probe/remove/shutdown calls, during "remove" we will unplug
> the
> device with opposite calls to "probe's" plug operations.
> For example i2c_add_adapter() from 'probe' and i2c_del_adapter() from
> 'remove'.
> For "shutdown", as system is going to shutdown, there is no need of
> unplug
> operations to be done.
>
> And also, I had a glance on other upstream i2c drivers, and noticed
> "i2c-i801.c"
> driver has i2c_del_adapter() called from remove callback but not from
> shutdown
> callback.

Sure, other drivers could also be broken.

>
> And actually I tried calling i2c_del_adapter() from geni_i2c_shutdown(),
> and it resulted in below WARNING trace
> [   90.320282] Call trace:
> [   90.322807]  _regulator_put+0xc4/0xcc
> [   90.326583]  regulator_bulk_free+0x48/0x6c
> [   90.330808]  devm_regulator_bulk_release+0x20/0x2c
> [   90.335744]  release_nodes+0x1d0/0x244
> [   90.339609]  devres_release_all+0x3c/0x54
> [   90.343735]  device_release_driver_internal+0x108/0x194
> [   90.349109]  device_release_driver+0x24/0x30
> [   90.353510]  bus_remove_device+0xd0/0xf4
> [   90.357548]  device_del+0x1a8/0x2f8
> [   90.361143]  device_unregister+0x1c/0x34
> [   90.365181]  __unregister_client+0x78/0x88
> [   90.369397]  device_for_each_child+0x64/0xb4
> [   90.373797]  i2c_del_adapter+0xf0/0x1d4
> [   90.377745]  geni_i2c_shutdown+0x9c/0xc0
> [   90.381783]  platform_drv_shutdown+0x28/0x34
> [   90.386182]  device_shutdown+0x148/0x1f0
>
> Can you please suggest me what might be missing here?
>

It looks like some device that is on the i2c bus is putting a regulator
in the remove path without disabling it. Can you print out which device
driver it is and fix that driver to call regulator_disable() on the
driver remove path? I'll try locally and see if I can find the driver
too.