Re: [PATCH 06/20] drm/msm: Use iommu_paging_domain_alloc()

[Baolu Lu]

On 5/29/24 4:21 PM, Dmitry Baryshkov wrote:
> On Wed, May 29, 2024 at 01:32:36PM +0800, Lu Baolu wrote:
> > The domain allocated in msm_iommu_new() is for the @dev. Replace
> > iommu_domain_alloc() with iommu_paging_domain_alloc() to make it explicit.
> >
> > Update msm_iommu_new() to always return ERR_PTR in failure cases instead
> > of NULL.
> Please don't mix unrelated changes, because ...
>
> > Signed-off-by: Lu Baolu<baolu.lu@xxxxxxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/msm/msm_iommu.c | 8 ++++----
> >   1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/msm_iommu.c b/drivers/gpu/drm/msm/msm_iommu.c
> > index d5512037c38b..f7e28d4b5f62 100644
> > --- a/drivers/gpu/drm/msm/msm_iommu.c
> > +++ b/drivers/gpu/drm/msm/msm_iommu.c
> > @@ -407,9 +407,9 @@ struct msm_mmu *msm_iommu_new(struct device *dev, unsigned long quirks)
> >   	struct msm_iommu *iommu;
> >   	int ret;
> >   
> > -	domain = iommu_domain_alloc(dev->bus);
> > -	if (!domain)
> > -		return NULL;
> > +	domain = iommu_paging_domain_alloc(dev);
> > +	if (IS_ERR(domain))
> > +		return ERR_CAST(domain);
> >   
> >   	iommu_set_pgtable_quirks(domain, quirks);
> >   
> > @@ -441,7 +441,7 @@ struct msm_mmu *msm_iommu_gpu_new(struct device *dev, struct msm_gpu *gpu, unsig
> >   	struct msm_mmu *mmu;
> >   
> >   	mmu = msm_iommu_new(dev, quirks);
> > -	if (IS_ERR_OR_NULL(mmu))
> > +	if (IS_ERR(mmu))
> >   		return mmu;
> NAK, not having an IOMMU is a poor but legit usecase for some of devices
> which don't have IOMMU support yet (for example because of the buggy
> implementation for which we were not able to get all the hooks in).
>
> Please don't break compatibility for existing platforms.

Sure. I will remove this line of change. Though I have no idea in which
case msm_iommu_new() could return NULL after this patch.

Best regards,
baolu