From 5ce4b59653b2c2053cd9a011918ac1e4747f24cc Mon Sep 17 00:00:00 2001 From: Josh Boyer Date: Tue, 17 Jun 2008 19:01:38 -0400 Subject: powerpc/4xx: Workaround for PPC440EPx/GRx PCI_28 Errata 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. Acked-by: Stefan Roese Signed-off-by: Josh Boyer --- arch/powerpc/sysdev/indirect_pci.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'arch/powerpc/sysdev/indirect_pci.c') diff --git a/arch/powerpc/sysdev/indirect_pci.c b/arch/powerpc/sysdev/indirect_pci.c index cfbd2aae93e8..7fd49c97501a 100644 --- a/arch/powerpc/sysdev/indirect_pci.c +++ b/arch/powerpc/sysdev/indirect_pci.c @@ -123,6 +123,12 @@ indirect_write_config(struct pci_bus *bus, unsigned int devfn, int offset, (bus->number == hose->first_busno)) val &= 0xffffff00; + /* Workaround for PCI_28 Errata in 440EPx/GRx */ + if ((hose->indirect_type & PPC_INDIRECT_TYPE_BROKEN_MRM) && + offset == PCI_CACHE_LINE_SIZE) { + val = 0; + } + /* * Note: the caller has already checked that offset is * suitably aligned and that len is 1, 2 or 4. -- cgit v1.2.3