From fb26592301200dbbe4a9943fe188b57a46716900 Mon Sep 17 00:00:00 2001 From: Bjorn Helgaas Date: Mon, 31 Oct 2016 16:00:01 -0500 Subject: PCI: Warn on possible RW1C corruption for sub-32 bit config writes Hardware that supports only 32-bit config writes is not spec-compliant. For example, if software performs a 16-bit write, we must do a 32-bit read, merge in the 16 bits we intend to write, followed by a 32-bit write. If the 16 bits we *don't* intend to write happen to have any RW1C (write-one- to-clear) bits set, we just inadvertently cleared something we shouldn't have. Add a rate-limited warning when we do sub-32 bit config writes. Remove similar probe-time warnings from some of the affected host bridge drivers. Signed-off-by: Bjorn Helgaas Enthusiastically-Acked-by: Russell King Acked-by: Shawn Lin # rockchip Acked-by: Thierry Reding --- drivers/pci/access.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) (limited to 'drivers/pci/access.c') diff --git a/drivers/pci/access.c b/drivers/pci/access.c index d11cdbb8fba3..db239547fefd 100644 --- a/drivers/pci/access.c +++ b/drivers/pci/access.c @@ -142,10 +142,22 @@ int pci_generic_config_write32(struct pci_bus *bus, unsigned int devfn, if (size == 4) { writel(val, addr); return PCIBIOS_SUCCESSFUL; - } else { - mask = ~(((1 << (size * 8)) - 1) << ((where & 0x3) * 8)); } + /* + * In general, hardware that supports only 32-bit writes on PCI is + * not spec-compliant. For example, software may perform a 16-bit + * write. If the hardware only supports 32-bit accesses, we must + * do a 32-bit read, merge in the 16 bits we intend to write, + * followed by a 32-bit write. If the 16 bits we *don't* intend to + * write happen to have any RW1C (write-one-to-clear) bits set, we + * just inadvertently cleared something we shouldn't have. + */ + dev_warn_ratelimited(&bus->dev, "%d-byte config write to %04x:%02x:%02x.%d offset %#x may corrupt adjacent RW1C bits\n", + size, pci_domain_nr(bus), bus->number, + PCI_SLOT(devfn), PCI_FUNC(devfn), where); + + mask = ~(((1 << (size * 8)) - 1) << ((where & 0x3) * 8)); tmp = readl(addr) & mask; tmp |= val << ((where & 0x3) * 8); writel(tmp, addr); -- cgit v1.2.3