| From | Arnd Bergmann <> | Subject | Re: [PATCH v2 00/16] ARM: support for ICP DAS LP-8x4x (with dts) | Date | Sat, 14 Dec 2013 22:03:45 +0100 |
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On Friday 13 December 2013, Sergei Ianovich wrote: > Fixed most review requirements. Details in respective patches. > > I've completely met the requirement for using dmaengine-based DMA > in patch v2-03/16. Tests showed new DMA was underperforming. It added > on top of a pre-existing problem with MMC bus width and made the system > barely usable. However, the new code in this patch work correctly with > both the existing and the new DMA. Even if the new DMA is compiled into > the kernel, the exisitng DMA initializes first.
As mentioned, I think this is a good approach, as long as it's coordinated with Daniel's patches for the dmaengine. I would expect that once we get to the bottom of this, there will only be a small overhead from not directly using the dma registers but going through the dmaengine API.
> I've also decided not to create a single mfd device for > machine-specific devices. Instead each type is supported by a separate > driver in respective subsystem. It was tempting to hardcode all the > constants in one source file, but that requires ugly initialization. > The taken way produces much cleaner code.
I think you should at least change the DT representation for the FPGA to show one device as the actual FPGA and attach children to that, multiple indirection levels if necessary.
I suspect that the fpga is on some external-bus port with a specific chip-select, so I would model this as
extbus { compatible = "simple-bus"; #address-cells = <1>; #size-cells = <1>; /* bus addresses 0-0xfffff mapped to 0x17000000 */ ranges = <0 0x17000000 0x100000>; interrupt-parent = <&fpga-irq>;
fpga-irq: irq@6 { regs = <6 16>; /* translated addresses ... };
fgpa-bus { #address-cells = <1>; #size-cells = <1>; ranges;
serial@9050 { ... }; }; };
I also think you don't need to make the devices quite as fine-grained here but instead group things together more. I would probably indeed put everything that is not on one of the slots into a common device, including the irqchip.
Arnd
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