[+to Marc] On Fri, Apr 29, 2022 at 09:42:52AM +0000, Conor.Dooley@xxxxxxxxxxxxx wrote: > On 28/04/2022 10:29, Lorenzo Pieralisi wrote: > > On Tue, Apr 05, 2022 at 12:17:51PM +0100, daire.mcnamara@xxxxxxxxxxxxx wrote: > >> From: Daire McNamara <daire.mcnamara@xxxxxxxxxxxxx> > >> > >> Clear MSI bit in ISTATUS register after reading it before > >> handling individual MSI bits > > > > That explains nothing. If you are fixing a bug please describe > > the issue and how the patch is fixing it. > > Someone in the pantheon of IT gods has it out for Daire, so I am > sending this on his behalf, but is the following revised commit > message better? > > Clear the MSI bit in ISTATUS register after reading it, but before > reading and handling individual MSI bits from the IMSI register. > This avoids a potential race where new MSI bits may be set on the > IMSI register after it was read and be missed when the MSI bit in > the ISTATUS register is cleared. "ISTATUS" doesn't appear in the code as a register name. Neither does "IMSI". Please use names that match the code. Honestly, I don't understand enough about IRQs to determine whether this is a correct fix. Hopefully Marc will chime in. All I really know how to do is compare all the drivers and see which ones don't fit the typical patterns. And speaking of that, I looked at all the users of irq_set_chained_handler_and_data() in drivers/pci. All the handlers except mc_handle_intx() and mc_handle_msi() call chained_irq_enter() and chained_irq_exit(). Are mc_handle_intx() and mc_handle_msi() just really special, or is this a mistake? > Reported-by: Bjorn Helgaas <helgaas@xxxxxxxxxx> Please use this address instead: Reported by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > Link: https://lore.kernel.org/linux-pci/20220127202000.GA126335@bhelgaas/ > Fixes: 6f15a9c9f941 ("PCI: microchip: Add Microchip PolarFire PCIe controller driver") > Signed-off-by: Daire McNamara <daire.mcnamara@xxxxxxxxxxxxx> > > >> This fixes a potential race condition pointed out by Bjorn Helgaas: > >> https://lore.kernel.org/linux-pci/20220127202000.GA126335@bhelgaas/ > >> > >> Fixes: 6f15a9c9f941 ("PCI: microchip: Add Microchip PolarFire PCIe controller driver") > >> Signed-off-by: Daire McNamara <daire.mcnamara@xxxxxxxxxxxxx> > >> --- > >> Adding linux-pci mailing list > >> drivers/pci/controller/pcie-microchip-host.c | 6 +----- > >> 1 file changed, 1 insertion(+), 5 deletions(-) > >> > >> diff --git a/drivers/pci/controller/pcie-microchip-host.c b/drivers/pci/controller/pcie-microchip-host.c > >> index 29d8e81e4181..da8e3fdc97b3 100644 > >> --- a/drivers/pci/controller/pcie-microchip-host.c > >> +++ b/drivers/pci/controller/pcie-microchip-host.c > >> @@ -416,6 +416,7 @@ static void mc_handle_msi(struct irq_desc *desc) > >> > >> status = readl_relaxed(bridge_base_addr + ISTATUS_LOCAL); > >> if (status & PM_MSI_INT_MSI_MASK) { > >> + writel_relaxed(status & PM_MSI_INT_MSI_MASK, bridge_base_addr + ISTATUS_LOCAL); > > > > What does ISTATUS_LOCAL contain vs ISTATUS_MSI ? If you explain that > > to me I could help you write the commit log. > > > > Thanks, > > Lorenzo > > > >> status = readl_relaxed(bridge_base_addr + ISTATUS_MSI); > >> for_each_set_bit(bit, &status, msi->num_vectors) { > >> ret = generic_handle_domain_irq(msi->dev_domain, bit); > >> @@ -432,13 +433,8 @@ static void mc_msi_bottom_irq_ack(struct irq_data *data) > >> void __iomem *bridge_base_addr = > >> port->axi_base_addr + MC_PCIE_BRIDGE_ADDR; > >> u32 bitpos = data->hwirq; > >> - unsigned long status; > >> > >> writel_relaxed(BIT(bitpos), bridge_base_addr + ISTATUS_MSI); > >> - status = readl_relaxed(bridge_base_addr + ISTATUS_MSI); > >> - if (!status) > >> - writel_relaxed(BIT(PM_MSI_INT_MSI_SHIFT), > >> - bridge_base_addr + ISTATUS_LOCAL); > >> } > >> > >> static void mc_compose_msi_msg(struct irq_data *data, struct msi_msg *msg) > >> -- > >> 2.25.1 > >>
