PCI: Reduce warnings on possible RW1C corruption

[ 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 fb265923, 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: fb265923 ("PCI: Warn on possible RW1C corruption for sub-32 bit config writes")
Link: https://lore.kernel.org/r/20200806041455.11070-1-mark.tomlinson@alliedtelesis.co.nz


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>