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PCI: Reduce warnings on possible RW1C corruption

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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 fb26592301, 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: fb26592301 ("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>
This commit is contained in:
Mark Tomlinson 2020-08-06 16:14:55 +12:00 committed by Bjorn Helgaas
parent 3dc8a1f6f6
commit 92c45b63ce
2 changed files with 7 additions and 3 deletions
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9
drivers/pci/access.c
View File

@ -159,9 +159,12 @@ 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;

1
include/linux/pci.h
View File

@ -668,6 +668,7 @@ 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)