[U-Boot] [PATCHv2 2/3] ARMv8/layerscape: Add FSL PPA support

[Scott Wood]

On Fri, 2016-01-22 at 20:27 +0000, Bhupesh Sharma wrote:
> 
> > -----Original Message-----
> > From: Scott Wood [mailto:oss at buserror.net]
> > Sent: Saturday, January 23, 2016 1:52 AM
> > To: york sun; Bhupesh Sharma; Zhiqiang Hou; u-boot at lists.denx.de;
> > albert.u.boot at aribaud.net; Mingkai.hu at freescale.com; Stuart Yoder;
> > leoli at freescale.com; prabhakar at freescale.com;
> > bhupesh.sharma at freescale.com; Zhiqiang Hou
> > Subject: Re: [PATCHv2 2/3] ARMv8/layerscape: Add FSL PPA support
> > 
> > On Fri, 2016-01-22 at 20:18 +0000, york sun wrote:
> > > On 01/22/2016 12:14 PM, Bhupesh Sharma wrote:
> > > > 
> > > > 
> > > > > -----Original Message-----
> > > > > From: Scott Wood [mailto:oss at buserror.net]
> > > > > Sent: Saturday, January 23, 2016 1:39 AM
> > > > > To: york sun; Zhiqiang Hou; u-boot at lists.denx.de;
> > > > > albert.u.boot at aribaud.net; Mingkai.hu at freescale.com; Stuart Yoder;
> > > > > leoli at freescale.com; prabhakar at freescale.com;
> > > > > bhupesh.sharma at freescale.com; Zhiqiang Hou
> > > > > Subject: Re: [PATCHv2 2/3] ARMv8/layerscape: Add FSL PPA support
> > > > > 
> > > > > On Fri, 2016-01-22 at 20:05 +0000, york sun wrote:
> > > > > > On 01/21/2016 01:53 AM, Zhiqiang Hou wrote:
> > > > > > > From: Hou Zhiqiang <Zhiqiang.Hou at freescale.com>
> > > > > > > 
> > > > > > > The FSL Primary Protected Application (PPA) is a software
> > > > > > > component loaded during boot which runs in TrustZone and
> > > > > > > remains resident after boot.
> > > > > > > 
> > > > > > > Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou at freescale.com>
> > > > > > > ---
> > > > > > > Tested on LS1043A RDB board
> > > > > > > 
> > > > > > 
> > > > > > I presume PSCI is implemented in PPA. How does the SMP boot flow
> > > > > > change with PPA? U-boot has to remain functional in the absence
> > > > > > of PPA,
> > > > > right?
> > > > > > 
> > > > > > Would it be possible to write a readme for PPA?
> > > > > 
> > > > > Also, how does the devicetree get updated to indicate the presence
> > > > > of PSCI?
> > > > > 
> > > > 
> > > > One needs to add PSCI node in the DTS for the same, claiming support
> > > > for PSCI specification.
> > > > The cpu.enable_method needs to be changed from spin-table to psci as
> > well.
> > > > 
> > > > See
> > > > http://lxr.free-electrons.com/source/Documentation/devicetree/bindin
> > > > gs
> > > > /arm/psci.txt for details.
> > > > 
> > > 
> > > Bhupesh,
> > > 
> > > Before PPA is fully adopted, u-boot has to detect the existence of PPA
> > > and decide to use PSCI or spin table, right? So the device tree node
> > > should also be fixed accordingly.
> 
> A static CONFIG_ flag is used for enabling the PPA support currently in
> QorIQ-LS u-boot code.
> 
> > 
> > How would U-Boot know what version of PSCI the loaded PPA supports?  Is
> > or could there be any metadata on the PPA image to convey such
> > information?
> 
> PSCI specifications support the PSCI_VERSION API which is implemented by PPA
> and it returns the PSCI_VERSION
> supported by PPA.

That does not answer the question unless we can assume that PPA always
implements PSCI >= 0.2.  And maybe there are other services worth advertising
in the device tree?  Some sort of metadata would be nice.

-Scott