From e37d269734ee9866bef3f965d4f545b86352f326 Mon Sep 17 00:00:00 2001 From: Mark Tomlinson Date: Thu, 6 Aug 2020 16:14:55 +1200 Subject: [PATCH] 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 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 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@alliedtelesis.co.nz Signed-off-by: Mark Tomlinson Signed-off-by: Bjorn Helgaas Reviewed-by: Florian Fainelli Reviewed-by: Rob Herring Acked-by: Scott Branden Signed-off-by: Sasha Levin --- 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 4693569..8d0d1f6 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 152a4d7..9d6e752 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -656,6 +656,7 @@ 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) -- 2.7.4