Re: [PATCH v10 09/23] iommu/io-pgtable-arm-v7s: Extend to support PA[33:32] for MediaTek

[Yong Wu]

On Wed, 2019-08-21 at 16:34 +0100, Robin Murphy wrote:
> On 21/08/2019 16:24, Will Deacon wrote:
> > On Wed, Aug 21, 2019 at 09:53:12PM +0800, Yong Wu wrote:
> >> MediaTek extend the arm v7s descriptor to support up to 34 bits PA where
> >> the bit32 and bit33 are encoded in the bit9 and bit4 of the PTE
> >> respectively. Meanwhile the iova still is 32bits.
> >>
> >> Regarding whether the pagetable address could be over 4GB, the mt8183
> >> support it while the previous mt8173 don't, thus keep it as is.
> >>
> >> Signed-off-by: Yong Wu <yong.wu@xxxxxxxxxxxx>
> >> ---
> >>   drivers/iommu/io-pgtable-arm-v7s.c | 32 +++++++++++++++++++++++++-------
> >>   include/linux/io-pgtable.h         |  7 +++----
> >>   2 files changed, 28 insertions(+), 11 deletions(-)
> > 
> > [...]
> > 
> >> @@ -731,7 +747,9 @@ static struct io_pgtable *arm_v7s_alloc_pgtable(struct io_pgtable_cfg *cfg,
> >>   {
> >>   	struct arm_v7s_io_pgtable *data;
> >>   
> >> -	if (cfg->ias > ARM_V7S_ADDR_BITS || cfg->oas > ARM_V7S_ADDR_BITS)
> >> +	if (cfg->ias > ARM_V7S_ADDR_BITS ||
> >> +	    (cfg->oas > ARM_V7S_ADDR_BITS &&
> >> +	     !(cfg->quirks & IO_PGTABLE_QUIRK_ARM_MTK_EXT)))
> > 
> > Please can you instead change arm_v7s_alloc_pgtable() so that it allows an
> > ias of up to 34 when the IO_PGTABLE_QUIRK_ARM_MTK_EXT is set?
> 
> You mean oas, right? I believe the hardware *does* actually support a 
> 32-bit ias as well, but we shouldn't pretend to support that while 
> __arm_v7s_alloc_table() still only knows how to allocate normal-sized 
> tables.

Yes. The HW double the lvl1 pgtable, thus it supports 33bit iova
actually. We may extend ias in the future.

> 
> Robin.
> 
> > 
> > With that change:
> > 
> > Acked-by: Will Deacon <will@xxxxxxxxxx>
> > 
> > Will
> > 
> 
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