Re: BUG: "iommu: Retire bus ops" breaks omap-iommu and omap3isp

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, Oct 08, 2024 at 10:08:27AM +0200, H. Nikolaus Schaller wrote:
> Hi Jason,
> 
> > Am 07.10.2024 um 14:15 schrieb Jason Gunthorpe <jgg@nvidia.com>:
> > 
> > On Sun, Oct 06, 2024 at 09:40:00AM +0200, H. Nikolaus Schaller wrote:
> >> Hi,
> >> 
> >> I found that the camera on our OMAP3 based system (GTA04) stopped working with v6.8-rc1.
> >> There was no bug in the camera driver but the OMAP3 ISP (image signal processor) emits
> >> 
> >> [   14.963684] omap3isp 480bc000.isp: failed to create ARM IOMMU mapping
> >> [   15.010192] omap3isp 480bc000.isp: unable to attach to IOMMU
> >> [   15.023376] omap3isp 480bc000.isp: isp_xclk_set_rate: cam_xclka set to 24685714 Hz (div 7)
> >> [   15.065399] omap3isp: probe of 480bc000.isp failed with error -12
> >> 
> >> Deeper analyses lead to this patch breaking operation. It is not fixed up to v6.12-rc1.
> >> 
> >> What seems to happen (in 6.8-rc1 code):
> >> 
> >> - omap_iommu_probe() passes &omap_iommu_ops to iommu_device_register()
> >> - iommu_device_register() stores the ops in iommu->ops (only)
> >> - __iommu_probe_device tries to read the ops from some fw_spec but not iommu->ops
> > 
> > Maybe like this?
> > 
> > @@ -1233,6 +1233,12 @@ static int omap_iommu_probe(struct platform_device *pdev)
> >               err = iommu_device_register(&obj->iommu, &omap_iommu_ops, &pdev->dev);
> >               if (err)
> >                       goto out_sysfs;
> > +               /*
> > +                * omap has a DT reprensetation but can't use the common DT
> > +                * code. Setting fwnode to NULL causes probe to be called for
> > +                * every device.
> > +                */
> > +               obj->iommu.fwnode = NULL;
> >               obj->has_iommu_driver = true;
> >       }
> 
> Doesn't seem to solve the problems:
> 
> root@letux:~# uname -a
> Linux letux 6.8.0-rc1-letux+ #19506 SMP PREEMPT Tue Oct  8 08:48:26 CEST 2024 armv7l GNU/Linux
> root@letux:~# dmesg|fgrep iommu
> [    0.402862] iommu: Default domain type: Translated
> [    0.402893] iommu: DMA domain TLB invalidation policy: strict mode
> [    0.405303] omap-iommu 480bd400.mmu: 480bd400.mmu registered
> [    0.405944] platform 480bc000.isp: Adding to iommu group 0

This seems like the isp device was bound to the iommu if the group was
create and the device attached to it? Does that mean it got past this problem:

	ops = iommu_fwspec_ops(dev_iommu_fwspec_get(dev));
	if (!ops)
		return -ENODEV;
?

> [   24.829071] omap3isp 480bc000.isp: iommu configuration for device failed with -ETIMEDOUT

This is strange? It is not upstream? Seems worth investigating what
this is..

Jason