Re: [PATCH] gpu: host1x: Free the IOMMU domain when there is no device to attach

[Mikko Perttunen]

On 07/11/2017 05:44 PM, Paul Kocialkowski wrote:
> On Tue, 2017-07-11 at 14:37 +0000, Marcel Ziswiler wrote:
> > On Tue, 2017-07-11 at 11:49 +0300, Paul Kocialkowski wrote:
> > > On Mon, 2017-07-10 at 21:33 +0200, Paul Kocialkowski wrote:
> > > > When there is no device to attach to the IOMMU domain, as may be
> > > > the
> > > > case when the device-tree does not contain the proper iommu node,
> > > > it
> > > > is
> > > > best to keep going without IOMMU support rather than failing.
> > > > This allows the driver to probe and function instead of taking
> > > > down
> > > > all of the tegra drm driver, leading to missing display support.
> > >
> > > Fixes: 404bfb78daf3 ("gpu: host1x: Add IOMMU support")
> > >
> > > > Signed-off-by: Paul Kocialkowski <contact-W9ppeneeCTY@xxxxxxxxxxxx
> > > > .
> > > > org>
> > > > ---
> > > >   drivers/gpu/host1x/dev.c | 8 +++++++-
> > > >   1 file changed, 7 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/gpu/host1x/dev.c b/drivers/gpu/host1x/dev.c
> > > > index ac65f52850a6..f296738d0de8 100644
> > > > --- a/drivers/gpu/host1x/dev.c
> > > > +++ b/drivers/gpu/host1x/dev.c
> > > > @@ -186,8 +186,13 @@ static int host1x_probe(struct
> > > > platform_device
> > > > *pdev)
> > > >   			return -ENOMEM;
> > > >   
> > > >   		err = iommu_attach_device(host->domain, &pdev-
> > > > > dev);
> > > >
> > > > -		if (err)
> > > > +		if (err == -ENODEV) {
> > > > +			iommu_domain_free(host->domain);
> > > > +			host->domain = NULL;
> > > > +			goto iommu_skip;
> > > > +		} else if (err) {
> > > >   			goto fail_free_domain;
> > > > +		}
> > > >   
> > > >   		geometry = &host->domain->geometry;
> > > >   
> > > > @@ -198,6 +203,7 @@ static int host1x_probe(struct platform_device
> > > > *pdev)
> > > >   		host->iova_end = geometry->aperture_end;
> > > >   	}
> > > >   
> > > > +iommu_skip:
> > > >   	err = host1x_channel_list_init(host);
> > > >   	if (err) {
> > > >   		dev_err(&pdev->dev, "failed to initialize channel
> > > > list\n");
> >
> > Please note that this does no longer cleanly apply after Mikko's 'gpu:
> > host1x: Refactor channel allocation code' commit from June 15 already
> > applied to current -next. Other than that
>
> Good to know! I intended this patch for fixing 4.12 stable, so I'm not
> even entirely sure it should land in next. The patch that fixes the
> device-tree to actually enable the iommu should be merged in priority.
>
> If that is the case and anyone wants this patch rebased to next, feel
> free to let me know and I'll send a rebased version.

We should definitely have this for non-stable kernels too - it would be 
a bit strange if the driver worked if IOMMU support wasn't built into 
the kernel but failed if it was :) It can also be helpful for debugging 
to be able to disable IOMMU just for host1x.

> > Tested-by: Marcel Ziswiler <marcel.ziswiler@xxxxxxxxxxx>
> > Tested-on: Apalis TK1, Apalis T30, Beaver, Colibri T30, Jetson-TK1
> >
> > Finally graphics working again, thanks guys!
>
> Yay! :)