FSL/NXP P5020: USB problems with the latest Git kernels

[Scott Wood]

On Wed, 2018-08-29 at 18:30 -0500, Scott Wood wrote:
> On Tue, 2018-08-28 at 20:13 +0100, Darren Stevens wrote:
> > Hello Scott
> > 
> > On 27/08/2018, Scott Wood wrote:
> > > On Mon, 2018-08-27 at 20:15 +0200, Christian Zigotzky wrote:
> > > > Hello,
> > > > 
> > > > Our users tested the RC1 of kernel 4.19 on their P5020 boards today.
> > > > Unfortunately the USB bug still exists. With mem values bigger than
> > > > 4096M,
> > > > the USB mouse and keyboard doesn't work. With the bootarg mem=4096M,
> > > > the
> > > > USB
> > > > devices work without any problems. Please compile the RC1 and test it
> > > > on
> > > > your P5020 board. There is a problem with the memory management since
> > > > 22/08/18. 
> > > 
> > > I just tested 4.19-rc1 on a T4240 and got a similar problem with
> > > MMC.  MMC
> > > and
> > > USB on these chips both have a 32-bit DMA limitation.  I'll look into
> > > it.
> > 
> > I've run a bisect locally on my system and found the following bad commit:
> > 
> > # first bad commit: [1b1eeca7e4c19fa76d409d4c7b338dba21f2df45] init: allow
> > initcall tables to be emitted using relative references
> > 
> > I can't see why this would fail though, and it only seems to affect fsl
> > machines, and on mine it killed the onboard sata as well.
> > 
> > Hope this helps.
> 
> 
> The patch is changing the order of initcalls.  swiotlb_setup_bus_notifier()
> and corenet_gen_publish_devices() are both machine_arch_initcall(), and if
> the
> latter happens before the former, then the bus notifier gets missed and
> swiotlb doesn't get used.

While it would be nice to fix this ordering dependency at some point, the
change was reverted on PPC by commit ff69279a44e9ba876466 ("powerpc: disable
support for relative ksymtab references").

-Scott