On 02/09/14 20:34, Arnd Bergmann wrote: > On Tuesday 02 September 2014 12:38:23 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. IIRC, the enabling and disabling bits are not >> specified either. >> >> Not having configurability is simply one variation on possible >> implementations. > > It's not obvious to me though that we are served better by a > pl011 driver that allows any possible subset of the features, > rather than having the existing driver for pl011, and a new driver > for the sbsa subset, which then won't allow any of the optional > features. > > Yes, there is some duplication, but a driver for this kind of > dumb console port should be doable in very little code, at > least less than the proposed implementation. I see your point, but as long as this means to introduce another serial prefix I would rather avoid it. As said in the other mail, I think the integration into PL011 does not look too bad, so we can discuss again this when I post the code later. Cheers, Andre. -- 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
