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SubjectRe: [PATCH v10 09/23] iommu/io-pgtable-arm-v7s: Extend to support PA[33:32] for MediaTek
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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 <yong.wu@mediatek.com>
>>> ---
>>> 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)

We shouldn't need to care about the size of phys_addr_t either way - the
fact is that the MTK format can still encode up to 34 bits of PA
regardless of whether callers can actually pass addresses that large.

Robin.

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