Re: [RFC v1 PATCH 1/2] of/pci: add of_pci_dma_configure() update dma configuration

[Murali Karicheri <m-karicheri2@ti.com>]

On 12/22/2014 05:24 PM, Arnd Bergmann wrote:
> On Monday 22 December 2014 16:40:43 Murali Karicheri wrote:
>>>> +++ b/arch/arm/mm/dma-mapping.c
>>>> @@ -2052,9 +2052,10 @@ void arch_setup_dma_ops(struct device *dev, u64
>>>> dma_base, u64 size,
>>>>                            struct iommu_ops *iommu, bool coherent)
>>>>     {
>>>>            struct dma_map_ops *dma_ops;
>>>> +       u64 temp_size = min((*(dev->dma_mask) + 1), size);
>>>>
>>>>            dev->archdata.dma_coherent = coherent;
>>>> -       if (arm_setup_iommu_dma_ops(dev, dma_base, size, iommu))
>>>> +       if (arm_setup_iommu_dma_ops(dev, dma_base, temp_size, iommu))
>>>>
>>>> If you agree, I will post v1 of the patch with these updates. Let me
>>>> know. I did some basic tests on Keystone with these changes and it works
>>>> fine.
>>>
>>> It's not exactly what I meant. My main point was that we need to limit
>>> dev->dma_mask to (size-1) here, but you are not touching that.
>>
>> if you mean overriding the dev->dma_mask to min((*dev->dma_mask),
>> size-1), then I am getting the error "Coherent DMA mask 0x7fffffff (pfn
>> 0x780000-0x800000) covers a smaller range of system memory than the DMA
>> zone pfn 0x0-0x880000) when the devices on Keystone tries to set the dma
>> mask. Something wrong and I need to look into the code.
>
> Right, it sounds like the offset was applied incorrectly at some point.
>
> What are the DMA zone size and the phys-offset?
2G and 0x8_0000_0000. This limit the usable DMA size to 2G on Keystone, 
I believe you shouldn't be limiting the dma mask to size-1 in this case, 
right? The DT setup the dma-range to have a size of 2G (0x80000000).

Murali
>
> 	Arnd


-- 
Murali Karicheri
Linux Kernel, Texas Instruments