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

[Andreas Kemnade <andreas@kemnade.info>]

Am Mon, 7 Oct 2024 09:15:43 -0300
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;
>         }
> 
hmm, that looks nice for a regression fix.

Does it make sense to adopt dt so that the common code can be used to
ease future maintenance?

Regards,
Andreas