Re: [PATCH v6 6/6] iommu/tegra-smmu: Add pagetable mappings to debugfs

[Dmitry Osipenko]

14.09.2021 21:49, Nicolin Chen пишет:
> On Tue, Sep 14, 2021 at 04:29:15PM +0300, Dmitry Osipenko wrote:
>> 14.09.2021 04:38, Nicolin Chen пишет:
>>> +static unsigned long pd_pt_index_iova(unsigned int pd_index, unsigned int pt_index)
>>> +{
>>> +	return ((dma_addr_t)pd_index & (SMMU_NUM_PDE - 1)) << SMMU_PDE_SHIFT |
>>> +	       ((dma_addr_t)pt_index & (SMMU_NUM_PTE - 1)) << SMMU_PTE_SHIFT;
>>> +}
>>
>> We know that IOVA is fixed to u32 for this controller. Can we avoid all
>> these dma_addr_t castings? It should make code cleaner a tad, IMO.
> 
> Tegra210 actually supports 34-bit IOVA...
> 

It doesn't. 34-bit is PA, 32-bit is VA.

Quote from T210 TRM:

"The SMMU is a centralized virtual-to-physical translation for MSS. It
maps a 32-bit virtual address to a 34-bit physical address. If the
client address is 40 bits then bits 39:32 are ignored."

Even if it supported more than 32bit, then the returned ulong is 32bit,
which doesn't make sense.