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Date: Tue, 15 Dec 2020 07:34:31 +1100
From: Stephen Rothwell <sfr@...b.auug.org.au>
To: Alex Deucher <alexdeucher@...il.com>,
Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Alex Deucher <alexander.deucher@....com>,
Jay Vosburgh <jay.vosburgh@...onical.com>,
Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@...ux.intel.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux Next Mailing List <linux-next@...r.kernel.org>,
Sean V Kelley <sean.v.kelley@...el.com>
Subject: Re: linux-next: manual merge of the amdgpu tree with the pci tree
Hi all,
On Tue, 8 Dec 2020 13:56:20 +1100 Stephen Rothwell <sfr@...b.auug.org.au> wrote:
>
> Today's linux-next merge of the amdgpu tree got a conflict in:
>
> drivers/pci/pcie/err.c
>
> between commits:
>
> 8f1bbfbc3596 ("PCI/ERR: Rename reset_link() to reset_subordinates()")
> 0791721d8007 ("PCI/ERR: Use "bridge" for clarity in pcie_do_recovery()")
> 05e9ae19ab83 ("PCI/ERR: Add pci_walk_bridge() to pcie_do_recovery()")
>
> from the pci tree and commit:
>
> 36a8901e900a ("PCI/ERR: Fix reset logic in pcie_do_recovery() call")
>
> from the amdgpu tree.
>
> I fixed it up (I think - see below) and can carry the fix as
> necessary. This is now fixed as far as linux-next is concerned, but any
> non trivial conflicts should be mentioned to your upstream maintainer
> when your tree is submitted for merging. You may also want to consider
> cooperating with the maintainer of the conflicting tree to minimise any
> particularly complex conflicts.
>
>
> diff --cc drivers/pci/pcie/err.c
> index 510f31f0ef6d,4a2735b70fa6..000000000000
> --- a/drivers/pci/pcie/err.c
> +++ b/drivers/pci/pcie/err.c
> @@@ -146,61 -146,49 +146,82 @@@ out
> return 0;
> }
>
> +/**
> + * pci_walk_bridge - walk bridges potentially AER affected
> + * @bridge: bridge which may be a Port, an RCEC, or an RCiEP
> + * @cb: callback to be called for each device found
> + * @userdata: arbitrary pointer to be passed to callback
> + *
> + * If the device provided is a bridge, walk the subordinate bus, including
> + * any bridged devices on buses under this bus. Call the provided callback
> + * on each device found.
> + *
> + * If the device provided has no subordinate bus, e.g., an RCEC or RCiEP,
> + * call the callback on the device itself.
> + */
> +static void pci_walk_bridge(struct pci_dev *bridge,
> + int (*cb)(struct pci_dev *, void *),
> + void *userdata)
> +{
> + if (bridge->subordinate)
> + pci_walk_bus(bridge->subordinate, cb, userdata);
> + else
> + cb(bridge, userdata);
> +}
> +
> pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> - pci_channel_state_t state,
> - pci_ers_result_t (*reset_link)(struct pci_dev *pdev))
> + pci_channel_state_t state,
> + pci_ers_result_t (*reset_subordinates)(struct pci_dev *pdev))
> {
> + int type = pci_pcie_type(dev);
> + struct pci_dev *bridge;
> pci_ers_result_t status = PCI_ERS_RESULT_CAN_RECOVER;
> - struct pci_bus *bus;
> + struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
>
> /*
> - * Error recovery runs on all subordinates of the first downstream port.
> - * If the downstream port detected the error, it is cleared at the end.
> + * If the error was detected by a Root Port, Downstream Port, RCEC,
> + * or RCiEP, recovery runs on the device itself. For Ports, that
> + * also includes any subordinate devices.
> + *
> + * If it was detected by another device (Endpoint, etc), recovery
> + * runs on the device and anything else under the same Port, i.e.,
> + * everything under "bridge".
> */
> - if (!(pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT ||
> - pci_pcie_type(dev) == PCI_EXP_TYPE_DOWNSTREAM))
> - dev = dev->bus->self;
> - bus = dev->subordinate;
> + if (type == PCI_EXP_TYPE_ROOT_PORT ||
> + type == PCI_EXP_TYPE_DOWNSTREAM ||
> + type == PCI_EXP_TYPE_RC_EC ||
> + type == PCI_EXP_TYPE_RC_END)
> + bridge = dev;
> + else
> + bridge = pci_upstream_bridge(dev);
>
> - pci_dbg(dev, "broadcast error_detected message\n");
> + pci_dbg(bridge, "broadcast error_detected message\n");
> if (state == pci_channel_io_frozen) {
> - pci_walk_bus(bus, report_frozen_detected, &status);
> + pci_walk_bridge(bridge, report_frozen_detected, &status);
> + /*
> + * After resetting the link using reset_link() call, the
> + * possible value of error status is either
> + * PCI_ERS_RESULT_DISCONNECT (failure case) or
> + * PCI_ERS_RESULT_NEED_RESET (success case).
> + * So ignore the return value of report_error_detected()
> + * call for fatal errors.
> + *
> + * In EDR mode, since AER and DPC Capabilities are owned by
> + * firmware, reported_error_detected() will return error
> + * status PCI_ERS_RESULT_NO_AER_DRIVER. Continuing
> + * pcie_do_recovery() with error status as
> + * PCI_ERS_RESULT_NO_AER_DRIVER will report recovery failure
> + * irrespective of recovery status. But successful reset_link()
> + * call usually recovers all fatal errors. So ignoring the
> + * status result of report_error_detected() also helps EDR based
> + * error recovery.
> + */
> - status = reset_link(dev);
> + status = reset_subordinates(bridge);
> - if (status != PCI_ERS_RESULT_RECOVERED) {
> + if (status == PCI_ERS_RESULT_RECOVERED) {
> + status = PCI_ERS_RESULT_NEED_RESET;
> + } else {
> + status = PCI_ERS_RESULT_DISCONNECT;
> - pci_warn(dev, "link reset failed\n");
> + pci_warn(bridge, "subordinate device reset failed\n");
> goto failed;
> }
> } else {
> @@@ -215,13 -203,25 +236,25 @@@
>
> if (status == PCI_ERS_RESULT_NEED_RESET) {
> /*
> - * TODO: Should call platform-specific
> - * functions to reset slot before calling
> - * drivers' slot_reset callbacks?
> + * TODO: Optimize the call to pci_reset_bus()
> + *
> + * There are two components to pci_reset_bus().
> + *
> + * 1. Do platform specific slot/bus reset.
> + * 2. Save/Restore all devices in the bus.
> + *
> + * For hotplug capable devices and fatal errors,
> + * device is already in reset state due to link
> + * reset. So repeating platform specific slot/bus
> + * reset via pci_reset_bus() call is redundant. So
> + * can optimize this logic and conditionally call
> + * pci_reset_bus().
> */
> + pci_reset_bus(dev);
> +
> status = PCI_ERS_RESULT_RECOVERED;
> - pci_dbg(dev, "broadcast slot_reset message\n");
> - pci_walk_bus(bus, report_slot_reset, &status);
> + pci_dbg(bridge, "broadcast slot_reset message\n");
> + pci_walk_bridge(bridge, report_slot_reset, &status);
> }
>
> if (status != PCI_ERS_RESULT_RECOVERED)
Just a reminder that this conflict still exists (the amdgpu tree commit
is now 400b308d388a).
--
Cheers,
Stephen Rothwell
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