On 2014年09月22日 23:54, Arnd Bergmann wrote:
On Monday 22 September 2014 17:15:06 Boris BREZILLON wrote:
- /* TODO(djkurtz): fetch the mapping start/size from somewhere */
- mapping = arm_iommu_create_mapping(&platform_bus_type, 0x10000000,
SZ_1G);- if (IS_ERR(mapping)) {
ret = PTR_ERR(mapping);goto err_config_cleanup;- }
- dma_set_coherent_mask(dev, DMA_BIT_MASK(32));
This is the default coherent mask. If you call this function, you should normally check the return value, or call dma_set_mask first, which you apparently don't do here, and in another place in this patch.
By "This is the default mask" do you mean it shouldn't be called at all ? Cause I ran into some trouble when not calling this in my atmel-hlcdc driver.
We used to get this wrong in the of_platform code, but it should work now.
Actually, in my case the platform device is created by the MFD core which seems to let the coherent_dma_mask uninitialized.
That may well be different, but it seems like a good idea to allow the MFD core to set this up as well.
In general, we expect that devices that are capable of doing DMA start with a 32-bit mask for both dma_mask and dma_coherent_mask, and a driver that requires a smaller masks or wants a larger mask has to call the appropriate interface to set these, and check the return value.
so I think we can use dma_set_mask_and_coherent(...) to set dma_mask and dma_coherent_mark at the same time, and check the return value.
Arnd