Re: [PATCH v2] dma-mapping: treat dev->bus_dma_mask as a DMA limit

Robin Murphy
2019-11-25T16:33:29Z

On 25/11/2019 7:44 am, Christoph Hellwig wrote:
> On Sat, Nov 23, 2019 at 09:51:08AM -0700, Nathan Chancellor wrote:
>> Just as an FYI, this introduces a warning on arm32 allyesconfig for me:
>
> I think the dma_limit argument to iommu_dma_alloc_iova should be a u64
> and/or we need to use min_t and open code the zero exception.
>
> Robin, Nicolas - any opinions?

Yeah, given that it's always held a mask I'm not entirely sure why it
was ever a dma_addr_t rather than a u64. Unless anyone else is desperate
to do it I'll get a cleanup patch ready for rc1.

> Also I wonder how this file gets compiled on arm32 given that arm32
> has its own set of iommu dma ops..

As long as the dependencies for CONFIG_IOMMU_DMA are met it can be built
even when it's not actually used. That said, I might have expected that
arm allyesconfig ends up with CONFIG_ARCH_DMA_ADDR_T_64BIT=y anyway; I
guess it must pick some of CONFIG_ARM_LPAE's negative dependencies.

(/me doesn't feel like jumping down the all*config rabbit hole today)

Robin.