[PATCH v2] ARM: dts: imx: Pass 'chosen' and 'memory' nodes

[Uwe Kleine-König]

On Thu, Jan 19, 2017 at 02:56:42PM +0000, Russell King - ARM Linux wrote:
> On Thu, Jan 19, 2017 at 03:46:41PM +0100, Uwe Kleine-König wrote:
> > On Thu, Jan 19, 2017 at 12:35:40PM -0200, Fabio Estevam wrote:
> > > Hi Uwe,
> > > 
> > > On Thu, Jan 19, 2017 at 12:13 PM, Uwe Kleine-König
> > > <u.kleine-koenig at pengutronix.de> wrote:
> > > 
> > > > Would it be nice to add a comment about why this was added? Something to
> > > > prevent a cleanup like "remove empty nodes and invalid memory
> > > > configurations".
> > > 
> > > Do you mean something like this?
> > > 
> > > /* "chosen" and "memory" nodes are mandatory */
> > > chosen {};
> > > memory { device_type = "memory"; reg = <0 0>; };
> > 
> > Not very helpful comment. Something like:
> > 
> > 	/*
> > 	 * The decompressor relies on a pre-existing chosen node to be
> > 	 * available to insert the command line and merge other ATAGS
> > 	 * info.
> > 	 */
> > 
> > Is it difficult to fix the decompressor?
> 
> ... and that comment would be wrong.  Yes, the decompressor relies on it,
> as do some uboot versions.

Good that we talked about this, otherwise I would have removed that once
the decompressor is fixed. So the comment must be

	/*
	 * The decompressor and also some versions of U-Boot rely on a
	 * pre-existing /chosen node to be available to insert the
	 * command line and merge other ATAGS info.
	 * Also for U-Boot there must be a pre-existing /memory node.
	 */
 
> > I didn't understood the breakage regarding the memory node good enough
> > to suggest a comment for that.
> 
> A missing memory node appears to prevent some uboot versions supplying
> any kind of memory layout to the kernel, which then causes the kernel to
> crash very early during boot.
> 
> Again, this is not using appended DTB - this is using a separately loaded
> DTB in uboot.  uboot fails to update the dtb if these nodes are missing.
> 
> Frankly, I think the original change (removing the skeleton.dtsi include)
> was misguided and needs to be reverted - the change is imho built upon an
> incorrect assumption that nothing in skeleton.dtsi is required.  That's
> clearly false.

I tend to agree as I assume it's not only U-Boot on i.MX but on all ARM
platforms.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |