On 13/10/2019 15:28, Daniele Alessandrelli wrote:
Hi,
It looks like dma_alloc_coherent() is setting the dma_handle output
parameter to the memory physical address and not the device bus
address when the device is using reserved memory regions for DMA
allocation. This is despite using 'dma_ranges' in the device tree to
describe the DMA memory mapping. Is this expected behavior or a bug?
That does sound like a bug :(
Here is a reduced version of the device tree I'm using:
\ {
reserved-memory {
#address-cells = <2>;
#size-cells = <2>;
ranges;
mydev_rsvd: rsvd_mem@494800000 {
compatible = "shared-dma-pool";
reg = <0x4 0x94800000 0x0 0x200000>;
no-map;
};
};
soc {
compatible = "simple-bus";
#address-cells = <2>;
#size-cells = <2>;
ranges;
dma_ranges;
mybus {
ranges = <>;
dma-ranges = <>;
compatible = "simple-bus";
#address-cells = <2>;
#size-cells = <2>;
ranges = <0x0 0x0 0x0 0x0 0x0 0x80000000>;
dma-ranges = <0x0 0x80000000 0x4 0x80000000
0x0 0x80000000>;
mydevice {
compatible = "my-compatible-string";
memory-region = <&mydev_rsvd>;
}
}
}
};
It looks like this issue was previously fixed by commit c41f9ea998f3
("drivers: dma-coherent: Account dma_pfn_offset when used with device
tree") which introduced a new function ('dma_get_device_base()') to
return the reserved memory address as seen by the device. However,
such a function, even if still there, is not used anymore in latest
code (as of v5.4-rc2). Was that done for a specific reason? Or is it
just a mistake?
Hmm, it looks like 43fc509c3efb ("dma-coherent: introduce interface for
default DMA pool") removed the caller of dma_get_device_base() in the
alloc path shortly after it was introduced, which certainly appears as
if it may have been unintentional - Vladimir?
Robin.
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
