On Thursday 17 July 2014 01:20:54 Peter Chen wrote: > Thanks, arnd. > > For chipidea generic glue layer case, if there are three devices who use this > driver, and all devices have 32-bit bus, some devices have less 32 address lines. > For example: > > - the device_a doesn't need to use dma_mask > - the device_b needs dma_mask as 0xfffffffff > - the device_c needs dma_mask as 0xfffffff0, assume it has only 28 address lines This makes no sense. You always need a dma mask, so the first case doesn't exist, and the second one is the default. In the third case, I assume you mean 0x0fffffff, which is a 28-bit mask. > My questions are: > - Can we not set dma_mask at driver, and only set dma-ranges at dts for device_b > and device_c as a solution to cover this different dma mask use case? try to understand my earlier reply. What is the problem with device_b? Is that a limitation of the bus it is connected to, or the version of the chipidea hardware? > - If we can't use this solution, would you suggest one? It depends on what the requirement of the hardware is, as I explained now for three times. > - If we can use this solution, for device_b and device_c, how can we write dma-ranges? > I can't find any arm platforms use it, only some powerpc platform use it. > According to the definition from Power_ePAPR_APPROVED_v1.1.pdf, it is > dma-ranges = <child-bus-address, parent-bus-address, length> > but I find the powerpc has different way for using dma-ranges. It's now handled by of_dma_configure() in drivers/of/platform.c for all architectures. Arnd -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
