Re: [edk2-devel] [PATCH 1/1] MdeModulePkg: UART Dynamic clock freq Support

["Ni, Ray" <ray.ni@intel.com>]

Leif,
Please understand that the concern of this change is all the platforms that uses
this serial port lib must be changed otherwise build breaks.

Ard,
Using Guided HOB sounds a good idea to me: )
The benefits of using HOB is:
  Length field in the HOB header can be used for extension if more parameters are needed.
  DXE can have the HOB access as well.

EFI_SEC_HOB_DATA_PPI can be used to return the new Guided HOB from SEC phase if needed.

Thanks,
Ray


> -----Original Message-----
> From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Sent: Monday, March 30, 2020 3:45 PM
> To: Leif Lindholm <leif@nuviainc.com>
> Cc: Jiang, Guomin <guomin.jiang@intel.com>; devel@edk2.groups.io; pankaj.bansal@nxp.com; Ni, Ray <ray.ni@intel.com>;
> Wang, Jian J <jian.j.wang@intel.com>; Wu, Hao A <hao.a.wu@intel.com>; Ma, Maurice <maurice.ma@intel.com>; Dong,
> Guo <guo.dong@intel.com>; You, Benjamin <benjamin.you@intel.com>; Meenakshi Aggarwal
> <meenakshi.aggarwal@nxp.com>; Varun Sethi <V.Sethi@nxp.com>; Samer El-Haj-Mahmoud <Samer.El-Haj-
> Mahmoud@arm.com>
> Subject: Re: [edk2-devel] [PATCH 1/1] MdeModulePkg: UART Dynamic clock freq Support
> 
> On Mon, 30 Mar 2020 at 09:35, Leif Lindholm <leif@nuviainc.com> wrote:
> >
> > Hi Jiang,
> >
> > It is not a question of effort of copying a driver, it is a question
> > that copying drivers is something that should be avoided wherever
> > practically possible. I did not think this topic was still under
> > debate.
> >
> > If the existing 16550 SerialPortLib is overspecialised to the point
> > where it only works on a subset of 16550 implementations, then it
> > should change. There are going to be more non-PC systems turning up
> > with 16550 UARTs - should they each copy/modify their drivers?
> >
> > If there are better ways of solving that problem, please suggest.
> > But more duplicated drivers is not the answer.
> >
> 
> Could we use a GUIDed HOB? If it exists, we use its contents, and if
> it doesn't, we use the default set by the FixedPCD.