Re: [PATCH] powerpc/85xx: DTS - re-organize the SPI partitions property

[Scott Wood <scottwood@freescale.com>]

On Tue, 2013-09-17 at 06:06 -0500, Hu Mingkai-B21284 wrote:
> Scott,
> Sorry for the delayed response.
> Please fine my comments.
> Thanks,
> Mingkai
> 
> > -----Original Message-----
> > From: Wood Scott-B07421
> > Sent: Thursday, September 12, 2013 9:16 AM
> > To: Hu Mingkai-B21284
> > Cc: Wood Scott-B07421; linuxppc-dev@ozlabs.org
> > Subject: Re: [PATCH] powerpc/85xx: DTS - re-organize the SPI partitions
> > property
> > 
> > On Tue, 2013-09-10 at 21:07 -0500, Hu Mingkai-B21284 wrote:
> > >
> > > > -----Original Message-----
> > > > From: Wood Scott-B07421
> > > > Sent: Wednesday, September 11, 2013 7:33 AM
> > > > To: Hu Mingkai-B21284
> > > > Cc: linuxppc-dev@ozlabs.org
> > > > Subject: Re: [PATCH] powerpc/85xx: DTS - re-organize the SPI
> > > > partitions property
> > > >
> > > > What happens to exsting users whose flash is laid out the existing
> > > > way, when they upgrade to these device trees?
> > > >
> > >
> > > The SPI flash layout should be mapping the new device tree.
> > >
> > > If the existing device tree is used to deploy the SPI flash, the
> > > following issues must be run into as the commit message described:
> > >
> > > 1. Kernel images would be overlapped with U-Boot image.
> > > 2. Kernel images would be overlapped with FMAN ucode.
> > > 3. Saving environment variables will crash the kernel image.
> > 
> > Has the SPI U-Boot image always been larger than 512K for all these
> > platforms?  Why, given that we're under 512K for other boot modes?
> > 
> 
> For DPAA platform, the ld script used to link the u-boot image is 
> "./arch/powerpc/cpu/mpc85xx/u-boot.lds" which will generate the 512K u-boot
> Image. This image will be split into 64bytes and appended PBL command for 
> Each 64bytes pieces, so the size of final image must be greater than 512K.

What is the entry point in SRAM when you load from PBL?  If it is (or
can be made to be) the beginning of the image rather than the end, then
turn off the resetvec and the fixed image size that results.

> > > > We really should not be putting partition layout info in the device
> > > > tree to begin with...
> > > >
> > > OK, I will remove the layout diagram in the commit message.
> > 
> > That's not what I meant.  I meant that the dts should be describing
> > hardware, and this is the sort of trouble we run into when we deviate
> > from that.  A better way would be to use the mtdparts command line option.
> > Even better would be some sort of on-flash partition table.
> > 
> 
> You're right, but maybe some customer has already used the device tree partition table...

My main point was to encourage us to shift away from this rather than to
rip it out right this instant.

-Scott