On Thu, Aug 22, 2019 at 11:08:58AM +0100, Robin Murphy wrote:
> On 2019-08-22 9:56 am, Yong Wu wrote:
> > On Wed, 2019-08-21 at 16:24 +0100, 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 <[email protected]>
> > > > ---
> > > > 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?
> >
> > Here I only simply skip the oas checking for our case. then which way do
> > your prefer? something like you commented before:?
> >
> >
> > if (cfg->ias > ARM_V7S_ADDR_BITS)
> > return NULL;
> >
> > if (cfg->quirks & IO_PGTABLE_QUIRK_ARM_MTK_EXT) {
> > if (!IS_ENABLED(CONFIG_PHYS_ADDR_T_64BIT))
> > cfg->oas = min(cfg->oas, ARM_V7S_ADDR_BITS);
> > else if (cfg->oas > 34)
> > return NULL;
> > } else if (cfg->oas > ARM_V7S_ADDR_BITS) {
> > return NULL;
> > }
>
> All it should take is something like:
>
> if (cfg->quirks & IO_PGTABLE_QUIRK_ARM_MTK_EXT)
> max_oas = 34;
> else
> max_oas = 32;
> if (cfg->oas > max_oas)
> return NULL;
>
> or even just:
>
> if (cfg->oas > 32 ||
> (cfg->quirks & IO_PGTABLE_QUIRK_ARM_MTK_EXT && cfg->oas > 34))
> return NULL;
>
> (and if we prefer the latter style, perhaps we could introduce some kind of
> "is_mtk_4gb()" helper to save on verbosity)
I wondered the same thing, but another place we'd want the check is in
iopte_to_paddr() which probably needs the PHYS_ADDR_T check to avoid GCC
warnings, although I didn't try it.
So if we did:
static bool cfg_mtk_ext_enabled(struct io_pgtable_cfg *cfg)
{
return IS_ENABLED(CONFIG_PHYS_ADDR_T_64BIT) &&
cfg->quirks & IO_PGTABLE_QUIRK_ARM_MTK_EXT;
}
Then I suppose we could do this in _alloc():
if (cfg->oas > cfg_mtk_ext_enabled(cfg) ? 34 : ARM_V7S_ADDR_BITS)
return NULL;
and then this in iopte_to_paddr():
[...]
paddr = pte & mask;
if (!cfg_mtk_ext_enabled(cfg))
return paddr;
if (pte & ARM_V7S_ATTR_MTK_PA_BIT32)
paddr |= ...
[...]
What do you reckon?
Will
