On Thu, Dec 20, 2012 at 11:40:11PM +0000, Russell King - ARM Linux wrote: > On Thu, Dec 20, 2012 at 04:54:38PM -0600, Jon Hunter wrote: > > On 12/20/2012 01:51 PM, Pratik Patel wrote: > > > Ok, so are you referring to making CoreSight devices register > > > with AMBA bus instead of platform bus keeping everything else > > > intact? > > > > Yes exactly. However, please note I am not saying that we should do > > this, and I asking what direction does the community want us to take > > here? Platform bus or AMBA bus? > > One of the issues which worries me about mixing peripheral drivers on > random different buses is... what happens when we end up with a SoC > which gates the APB clock at bus level (there are SoCs which gate the > APB clock at peripheral level.) In other words, an APB bus only gets > clocked upon request. > > We can deal with that with the infrastructure we have in place in the > AMBA bus layer, but not with the platform bus - we'd have to teach the > platform bus driver about the special APB clock instead of having it > handled primerily at the bus layer. > > At least the coresight ETM peripherals make use of the APB bus. They > have a whole pile of registers on the APB bus, and they have the > primecell IDs stored in the last words of the peripheral, again just > like the other primecell devices we have using the AMBA bus layer. > > What I'd say is... why stick it on a different bus type from the other > peripherals which might make things harder in the future? Thanks for the info. I will look into using the AMBA bus instead of the platform bus but one issue I notice is that AMBA framework seems to support one contiguous register space. CoreSight STM typically has a config register space and a stimulus port/channel register space and these can be non-contiguous in the chip memory map. -- Employee of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
