Re: [PATCH] iommu/arm: Cleanup resources in case of probe error path

[Robin Murphy]

On 2021-06-30 14:48, Marek Szyprowski wrote:
> On 30.06.2021 14:59, Will Deacon wrote:
> > On Wed, Jun 30, 2021 at 02:48:15PM +0200, Marek Szyprowski wrote:
> > > On 08.06.2021 18:45, Amey Narkhede wrote:
> > > > If device registration fails, remove sysfs attribute
> > > > and if setting bus callbacks fails, unregister the device
> > > > and cleanup the sysfs attribute.
> > > >
> > > > Signed-off-by: Amey Narkhede <ameynarkhede03@xxxxxxxxx>
> > > This patch landed in linux-next some time ago as commit 249c9dc6aa0d
> > > ("iommu/arm: Cleanup resources in case of probe error path"). After
> > > bisecting and some manual searching I finally found that it is
> > > responsible for breaking s2idle on DragonBoard 410c. Here is the log
> > > (captured with no_console_suspend):
> > >
> > > # time rtcwake -s10 -mmem
> > > rtcwake: wakeup from "mem" using /dev/rtc0 at Thu Jan  1 00:02:13 1970
> > > PM: suspend entry (s2idle)
> > > Filesystems sync: 0.002 seconds
> > > Freezing user space processes ... (elapsed 0.006 seconds) done.
> > > OOM killer disabled.
> > > Freezing remaining freezable tasks ... (elapsed 0.004 seconds) done.
> > > Unable to handle kernel NULL pointer dereference at virtual address
> > > 0000000000000070
> > > Mem abort info:
> > >      ESR = 0x96000006
> > >      EC = 0x25: DABT (current EL), IL = 32 bits
> > >      SET = 0, FnV = 0
> > >      EA = 0, S1PTW = 0
> > >      FSC = 0x06: level 2 translation fault
> > > Data abort info:
> > >      ISV = 0, ISS = 0x00000006
> > >      CM = 0, WnR = 0
> > > user pgtable: 4k pages, 48-bit VAs, pgdp=000000008ad08000
> > > [0000000000000070] pgd=0800000085c3c003, p4d=0800000085c3c003,
> > > pud=0800000088dcf003, pmd=0000000000000000
> > > Internal error: Oops: 96000006 [#1] PREEMPT SMP
> > > Modules linked in: bluetooth ecdh_generic ecc rfkill ipv6 ax88796b
> > > venus_enc venus_dec videobuf2_dma_contig asix crct10dif_ce adv7511
> > > snd_soc_msm8916_analog qcom_spmi_temp_alarm rtc_pm8xxx qcom_pon
> > > qcom_camss qcom_spmi_vadc videobuf2_dma_sg qcom_vadc_common msm
> > > venus_core v4l2_fwnode v4l2_async snd_soc_msm8916_digital
> > > videobuf2_memops snd_soc_lpass_apq8016 snd_soc_lpass_cpu v4l2_mem2mem
> > > snd_soc_lpass_platform snd_soc_apq8016_sbc videobuf2_v4l2
> > > snd_soc_qcom_common qcom_rng videobuf2_common i2c_qcom_cci qnoc_msm8916
> > > videodev mc icc_smd_rpm mdt_loader socinfo display_connector rmtfs_mem
> > > CPU: 1 PID: 1522 Comm: rtcwake Not tainted 5.13.0-next-20210629 #3592
> > > Hardware name: Qualcomm Technologies, Inc. APQ 8016 SBC (DT)
> > > pstate: 80000005 (Nzcv daif -PAN -UAO -TCO BTYPE=--)
> > > pc : msm_runtime_suspend+0x1c/0x60 [msm]
> > > lr : msm_pm_suspend+0x18/0x38 [msm]
> > > ...
> > > Call trace:
> > >     msm_runtime_suspend+0x1c/0x60 [msm]
> > >     msm_pm_suspend+0x18/0x38 [msm]
> > >     dpm_run_callback+0x84/0x378
> > I wonder if we're missing a pm_runtime_disable() call on the failure path?
> > i.e. something like the diff below...
>
> I've checked and it doesn't fix anything.

What's happened previously? Has an IOMMU actually failed to probe, or is 
this a fiddly "code movement unveils latent bug elsewhere" kind of 
thing? There doesn't look to be much capable of going wrong in 
msm_runtime_suspend() itself, so is the DRM driver also in a broken 
half-probed state where it's left its pm_runtime_ops behind without its 
drvdata being valid?

Robin.

> > Will
> >
> > --->8
> >
> > diff --git a/drivers/iommu/arm/arm-smmu/qcom_iommu.c b/drivers/iommu/arm/arm-smmu/qcom_iommu.c
> > index 25ed444ff94d..ce8f354755d0 100644
> > --- a/drivers/iommu/arm/arm-smmu/qcom_iommu.c
> > +++ b/drivers/iommu/arm/arm-smmu/qcom_iommu.c
> > @@ -836,14 +836,14 @@ static int qcom_iommu_device_probe(struct platform_device *pdev)
> >           ret = devm_of_platform_populate(dev);
> >           if (ret) {
> >                   dev_err(dev, "Failed to populate iommu contexts\n");
> > -               return ret;
> > +               goto err_pm_disable;
> >           }
> >    
> >           ret = iommu_device_sysfs_add(&qcom_iommu->iommu, dev, NULL,
> >                                        dev_name(dev));
> >           if (ret) {
> >                   dev_err(dev, "Failed to register iommu in sysfs\n");
> > -               return ret;
> > +               goto err_pm_disable;
> >           }
> >    
> >           ret = iommu_device_register(&qcom_iommu->iommu, &qcom_iommu_ops, dev);
> > @@ -869,6 +869,9 @@ static int qcom_iommu_device_probe(struct platform_device *pdev)
> >    
> >    err_sysfs_remove:
> >           iommu_device_sysfs_remove(&qcom_iommu->iommu);
> > +
> > +err_pm_disable:
> > +       pm_runtime_disable(dev);
> >           return ret;
> >    }
> Best regards