Hi Rob, On 02/09/14 18:38, Rob Herring wrote: > On Tue, Sep 2, 2014 at 8:48 AM, Arnd Bergmann <arnd@xxxxxxxx> wrote: >> On Tuesday 02 September 2014 08:20:53 Rob Herring wrote: >>>>> >>>>> This alone is not okay. There is no such implementation of hardware. >>>> >>>> But the SBSA explicitly allows this. I don't know of any vendor who just >>>> implements the subset, but I've been told that this has been asked for. >>> >>> To use baudrate as an example, that must be configurable somehow >>> either with pl011 registers or in a vendor specific way. I suppose you >>> could do an actual implementation with all those things hardcoded in >>> the design, but that seems unlikely. >> >> Why does the baudrate need to be configurable? I think it's completely >> reasonable to specify a console port that has a fixed (as in the >> OS must not care) rate, and that can be implemented either as a UART >> with a programmable rate or as a set of registers that directly talks >> to a remote system management device over whatever hardware protocol >> they choose. > > Sure. It is also completely reasonable that baudrate is configurable > and vendors can implement it however they choose since the SBSA does > not specify it. But this would be a different driver for a different hardware then and not covered by the SBSA version - so to some degree not our problem ;-) I don't see how we could really cover this problem for every possibly upcoming implementation. If I got the spec correctly, then exposing the baudrate setting for SBSA hardware is not meaningful in the sense of the spec. If you want to go with a configurable UART complying to the spec, you'd probably use a full featured PL011. > IIRC, the enabling and disabling bits are not > specified either. Correct, also the FIFO is always on and the word format is fixed to 8n1. Regards, Andre. > > Not having configurability is simply one variation on possible implementations. > > Rob > -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
