From: Mark Tomlinson mark.tomlinson@alliedtelesis.co.nz
[ Upstream commit 92c45b63ce22c8898aa41806e8d6692bcd577510 ]
For hardware that only supports 32-bit writes to PCI there is the possibility of clearing RW1C (write-one-to-clear) bits. A rate-limited messages was introduced by fb2659230120, but rate-limiting is not the best choice here. Some devices may not show the warnings they should if another device has just produced a bunch of warnings. Also, the number of messages can be a nuisance on devices which are otherwise working fine.
Change the ratelimit to a single warning per bus. This ensures no bus is 'starved' of emitting a warning and also that there isn't a continuous stream of warnings. It would be preferable to have a warning per device, but the pci_dev structure is not available here, and a lookup from devfn would be far too slow.
Suggested-by: Bjorn Helgaas helgaas@kernel.org Fixes: fb2659230120 ("PCI: Warn on possible RW1C corruption for sub-32 bit config writes") Link: https://lore.kernel.org/r/20200806041455.11070-1-mark.tomlinson@alliedtelesi... Signed-off-by: Mark Tomlinson mark.tomlinson@alliedtelesis.co.nz Signed-off-by: Bjorn Helgaas bhelgaas@google.com Reviewed-by: Florian Fainelli f.fainelli@gmail.com Reviewed-by: Rob Herring robh@kernel.org Acked-by: Scott Branden scott.branden@broadcom.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/pci/access.c | 9 ++++++--- include/linux/pci.h | 1 + 2 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/drivers/pci/access.c b/drivers/pci/access.c index 0914ddeae17f..c909c66a63e2 100644 --- a/drivers/pci/access.c +++ b/drivers/pci/access.c @@ -160,9 +160,12 @@ int pci_generic_config_write32(struct pci_bus *bus, unsigned int devfn, * 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); + if (!bus->unsafe_warn) { + dev_warn(&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); + bus->unsafe_warn = 1; + }
mask = ~(((1 << (size * 8)) - 1) << ((where & 0x3) * 8)); tmp = readl(addr) & mask; diff --git a/include/linux/pci.h b/include/linux/pci.h index bc35b15efadd..fc343d123127 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -604,6 +604,7 @@ struct pci_bus { struct bin_attribute *legacy_io; /* Legacy I/O for this bus */ struct bin_attribute *legacy_mem; /* Legacy mem */ unsigned int is_added:1; + unsigned int unsafe_warn:1; /* warned about RW1C config write */ };
#define to_pci_bus(n) container_of(n, struct pci_bus, dev)