Re: [PATCH v6 05/07] iommu/ipmmu-vmsa: Add new IOMMU_DOMAIN_DMA ops

Laurent Pinchart
2016-11-11T01:50:44Z

Hi Robin,

On Friday 21 Oct 2016 18:52:53 Robin Murphy wrote:
> On 20/10/16 00:36, Magnus Damm wrote:
> > From: Magnus Damm <damm+renesas@opensource.se>
> >
> > Introduce an alternative set of iommu_ops suitable for 64-bit ARM
> > as well as 32-bit ARM when CONFIG_IOMMU_DMA=y. Also adjust the
> > Kconfig to depend on ARM or IOMMU_DMA.
> >
> > Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
> > ---
> >
> > Changes since V5:
> > - Made domain allocation/free code more consistent - thanks Joerg!
> >
> > Changes since V4:
> > - Added Kconfig hunk to depend on ARM or IOMMU_DMA
> >
> > Changes since V3:
> > - Removed group parameter from ipmmu_init_platform_device()
> >
> > Changes since V2:
> >
> > - Included this new patch from the following series:
> > [PATCH 00/04] iommu/ipmmu-vmsa: IPMMU CONFIG_IOMMU_DMA update
> >
> > - Use only a single iommu_ops structure with #ifdef CONFIG_IOMMU_DMA
> > - Folded in #ifdefs to handle CONFIG_ARM and CONFIG_IOMMU_DMA
> > - of_xlate() is now used without #ifdefs
> > - Made sure code compiles on both 32-bit and 64-bit ARM.
> >
> > drivers/iommu/Kconfig | 1
> > drivers/iommu/ipmmu-vmsa.c | 122 ++++++++++++++++++++++++++++++++++++---
> > 2 files changed, 115 insertions(+), 8 deletions(-)

[snip]

> > --- 0006/drivers/iommu/ipmmu-vmsa.c
> > +++ work/drivers/iommu/ipmmu-vmsa.c 2016-10-20 08:16:48.440607110 +0900

[snip]

> > -static struct iommu_domain *ipmmu_domain_alloc(unsigned type)
> > -{
> > - if (type != IOMMU_DOMAIN_UNMANAGED)
> > - return NULL;
>
> I *think* that if we did the initial check thus:
>
> if (type != IOMMU_DOMAIN_UNMANAGED ||
> (IS_ENABLED(CONFIG_IOMMU_DMA) && type != IOMMU_DOMAIN_DMA))
> return NULL;

I assume you meant

if (type != IOMMU_DOMAIN_UNMANAGED &&
(!IS_ENABLED(CONFIG_IOMMU_DMA) || type != IOMMU_DOMAIN_DMA))
return NULL;

But how about just

if (type != IOMMU_DOMAIN_UNMANAGED && type != IOMMU_DOMAIN_DMA))
return NULL;

as type will never be set to IOMMU_DOMAIN_DMA on ARM32 ?

> it shouldn't be necessary to split the function at all - we then just
> wrap the {get,put}_cookie() bits in "if (type == IOMMU_DOMAIN_DMA)" and
> in the 32-bit ARM case they just don't run as that can never be true.
>
> > -
> > - return __ipmmu_domain_alloc(type);
> > -}
> > -

--
Regards,

Laurent Pinchart