diff options
| author | Bjorn Helgaas <bhelgaas@google.com> | 2016-10-31 16:00:01 -0500 |
|---|---|---|
| committer | Bjorn Helgaas <bhelgaas@google.com> | 2016-11-21 16:25:39 -0600 |
| commit | fb26592301200dbbe4a9943fe188b57a46716900 (patch) | |
| tree | 5688b579fea3e33a47263646c4b24f914334b8e8 /drivers/pci/access.c | |
| parent | 702ed3be1b1bf4dea05954168321741c0910c645 (diff) | |
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 <bhelgaas@google.com>
Enthusiastically-Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Acked-by: Shawn Lin <shawn.lin@rock-chips.com> # rockchip
Acked-by: Thierry Reding <treding@nvidia.com>
Diffstat (limited to 'drivers/pci/access.c')
| -rw-r--r-- | drivers/pci/access.c | 16 |
1 files changed, 14 insertions, 2 deletions
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); |