[edk2-devel] [PATCH edk2-platforms v3 16/24] Silicon/NXP: Add Chassis2 Package

[Leif Lindholm]

On Fri, Apr 24, 2020 at 02:42:13 +0000, Pankaj Bansal (OSS) wrote:
> > > > Why would multiple modules need to initialize the serial port?
> > >
> > > That's how the DebugLib has been designed.
> > > DebugLib is used by all modules to print info on console.
> > > BaseDebugLibSerialPortConstructor calls SerialPortInitialize.
> > > So SerialPortInitialize is called by all the modules.
> > 
> > Sure, but the bit where ChassisLib returns the active clock
> > configuration does not need to happen for each initialization.
> > That value can be cached.
> 
> The only mechanism I know for passing a cached value between different modules
> is either use PCDs or use HOBs.
> We have already explored both in https://edk2.groups.io/g/devel/message/57254
> and https://edk2.groups.io/g/devel/message/56530 

That was discussing what to do with regards to the generic 16550
driver. If we go with Laszlo's suggestion[1] for a separate
SerialUartClockLib instead of adding a vendor GUID HOB *into the
generic driver*, that does not preclude your using a HOB to cache the
value in your platform code for later use in your own
SerialUartClockLib implementation.

[1] https://edk2.groups.io/g/devel/message/56767

> Moreover the compiler can optimize the PcdDcfgBigEndian evaluation.
> So no overhead would be observed in evaluating PcdDcfgBigEndian in every call.

I don't question that, but that was always going to be the case anyway
- especially with LTO. The point is reducing code duplication -
especially for weird and wacky hardware workarounds.

/
    Leif

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