[Letux-kernel] [PATCH] PCI: imx6: install the fault handler only if we are really running on a compatible device
helgaas at kernel.org
Wed Mar 8 19:49:22 CET 2023
On Tue, Feb 28, 2023 at 09:43:54AM +0100, H. Nikolaus Schaller wrote:
> commit bb38919ec56e ("PCI: imx6: Add support for i.MX6 PCIe controller")
> added a fault hook to this driver in the probe function. So it was only
> installed if needed.
> commit bde4a5a00e76 ("PCI: imx6: Allow probe deferral by reset GPIO")
> moved it from probe to driver init which installs the hook unconditionally
> as soon as the driver is compiled into a kernel.
> When this driver is compiled as a module, the hook is not registered
> until after the driver has been matched with a .compatible and
> commit 415b6185c541 ("PCI: imx6: Fix config read timeout handling")
> extended the fault handling code.
> commit 2d8ed461dbc9 ("PCI: imx6: Add support for i.MX8MQ")
> added some protection for non-ARM architectures, but this does not
> protect non-i.MX ARM architectures.
Are *all* these commits relevant? Question also applies to Fixes:
> Since fault handlers can be triggered on any architecture for different
> reasons, there is no guarantee that they will be triggered only for the
> assumed situation, leading to improper error handling (i.MX6-specific
> imx6q_pcie_abort_handler) on foreign systems.
> I had seen strange L3 imprecise external abort messages several times on
> OMAP4 and OMAP5 devices and couldn't make sense of them until I realized
> they were related to this unused imx6q driver because I had
Apparently imx6q_pcie_abort_handler() assumes it is always called
because of a PCI abort? If so, that sounds problematic.
If non-PCI imprecise aborts happen on OMAP4 and OMAP5 where imx6q is
unused and imx6q_pcie_abort_handler() is not appropriate, I assume
similar non-PCI aborts can also happen on systems where imx6q *is*
So imx6q_pcie_abort_handler() may be trying to fixup non-PCI aborts
when it shouldn't?
> Note that CONFIG_PCI_IMX6=y is useful for kernel binaries that are designed
> to run on different ARM SoC and be differentiated only by device tree
> binaries. So turning off CONFIG_PCI_IMX6 is not a solution.
> Therefore we check the compatible in the init function before registering
> the fault handler.
> Fixes: bde4a5a00e76 ("PCI: imx6: Allow probe deferral by reset GPIO")
> Fixes: 415b6185c541 ("PCI: imx6: Fix config read timeout handling")
> Fixes: 2d8ed461dbc9 ("PCI: imx6: Add support for i.MX8MQ")
> Signed-off-by: H. Nikolaus Schaller <hns at goldelico.com>
> drivers/pci/controller/dwc/pci-imx6.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 1dde5c579edc8..89774aa187ae8 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -1402,6 +1402,15 @@ DECLARE_PCI_FIXUP_CLASS_HEADER(PCI_VENDOR_ID_SYNOPSYS, 0xabcd,
> static int __init imx6_pcie_init(void)
> #ifdef CONFIG_ARM
> + const struct of_device_id *reboot_id;
> + struct device_node *np;
> + np = of_find_matching_node_and_match(NULL, imx6_pcie_of_match,
> + &reboot_id);
Since you don't need reboot_id, I think you should use
> + if (!np)
> + return -ENODEV;
> + of_node_put(np);
> * Since probe() can be deferred we need to make sure that
> * hook_fault_code is not called after __init memory is freed
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