Re: [PATCH] powerpc/4xx: Workaround for PPC440EPx/GRx PCI_28 Errata

[Josh Boyer <jwboyer@linux.vnet.ibm.com>]

On Thu, 12 Jun 2008 16:24:13 +0200
Stefan Roese <sr@denx.de> wrote:

> On Wednesday 11 June 2008, Josh Boyer wrote:
> > The 440EPx/GRx chips don't support PCI MRM commands.  Drivers determine
> > this by looking for a zero value in the PCI cache line size register. 
> > However, some drivers write to this register upon initialization.  This can
> > cause MRMs to be used on these chips, which may cause deadlocks on PLB4.
> >
> > The workaround implemented here introduces a new indirect_type flag, called
> > PPC_INDIRECT_TYPE_BROKEN_MRM.  This is set in the pci_controller structure
> > in the pci fixup function for 4xx PCI bridges by determining if the bridge
> > is compatible with 440EPx/GRx.  The flag is checked in the
> > indirect_write_config function, and forces any writes to the
> > PCI_CACHE_LINE_SIZE register to be zero, which will disable MRMs for these
> > chips.
> >
> > A similar workaround has been tested by AMCC on various PCI cards, such as
> > the Silicon Image ATA card and Intel E1000 GIGE card.  Hangs were seen with
> > the Silicon Image card, and MRMs were seen on the bus with a PCI analyzer.
> > With the workaround in place, the card functioned properly and only Memory
> > Reads were seen on the bus with the analyzer.
> >
> > Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
> 
> Acked-by: Stefan Roese <sr@denx.de>
> 
> I manually applied your patch (since it doesn't apply clean as discussed on 
> IRC) and tested it on my Sequoia with a modified PCI USB driver changing 
> PCI_CACHE_LINE_SIZE.

Thanks.  I blame git for being dumb.  I guess I'll have to switch to
using git-format-patch instead of quilt.

In the meantime, I'll queue this up for .27.

josh