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Date: Fri, 9 Oct 2020 12:57:45 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Sean V Kelley <seanvk.dev@...gontracks.org>
Cc: bhelgaas@...gle.com, Jonathan.Cameron@...wei.com,
rafael.j.wysocki@...el.com, ashok.raj@...el.com,
tony.luck@...el.com, sathyanarayanan.kuppuswamy@...el.com,
qiuxu.zhuo@...el.com, linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org,
Sean V Kelley <sean.v.kelley@...el.com>
Subject: Re: [PATCH v8 11/14] PCI/RCEC: Add RCiEP's linked RCEC to AER/ERR
On Fri, Oct 02, 2020 at 11:47:32AM -0700, Sean V Kelley wrote:
> From: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
>
> When attempting error recovery for an RCiEP associated with an RCEC device,
> there needs to be a way to update the Root Error Status, the Uncorrectable
> Error Status and the Uncorrectable Error Severity of the parent RCEC.
> In some non-native cases in which there is no OS visible device
> associated with the RCiEP, there is nothing to act upon as the firmware
> is acting before the OS. So add handling for the linked 'rcec' in AER/ERR
> while taking into account non-native cases.
>
> Co-developed-by: Sean V Kelley <sean.v.kelley@...el.com>
> Signed-off-by: Sean V Kelley <sean.v.kelley@...el.com>
> Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> ---
> drivers/pci/pcie/aer.c | 9 +++++----
> drivers/pci/pcie/err.c | 39 ++++++++++++++++++++++++++++-----------
> 2 files changed, 33 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index 65dff5f3457a..dccdba60b5d9 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -1358,17 +1358,18 @@ static int aer_probe(struct pcie_device *dev)
> static pci_ers_result_t aer_root_reset(struct pci_dev *dev)
> {
> int aer = dev->aer_cap;
> + int rc = 0;
> u32 reg32;
> - int rc;
> -
>
> /* Disable Root's interrupt in response to error messages */
> pci_read_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, ®32);
> reg32 &= ~ROOT_PORT_INTR_ON_MESG_MASK;
> pci_write_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, reg32);
>
> - rc = pci_bus_error_reset(dev);
> - pci_info(dev, "Root Port link has been reset\n");
> + if (pci_pcie_type(dev) != PCI_EXP_TYPE_RC_EC) {
> + rc = pci_bus_error_reset(dev);
> + pci_info(dev, "Root Port link has been reset\n");
> + }
>
> /* Clear Root Error Status */
> pci_read_config_dword(dev, aer + PCI_ERR_ROOT_STATUS, ®32);
> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
> index 38abd7984996..956ad4c86d53 100644
> --- a/drivers/pci/pcie/err.c
> +++ b/drivers/pci/pcie/err.c
> @@ -149,7 +149,8 @@ static int report_resume(struct pci_dev *dev, void *data)
> /**
> * pci_walk_bridge - walk bridges potentially AER affected
> * @bridge bridge which may be an RCEC with associated RCiEPs,
> - * an RCiEP associated with an RCEC, or a Port.
> + * or a Port.
> + * @dev an RCiEP lacking an associated RCEC.
> * @cb callback to be called for each device found
> * @userdata arbitrary pointer to be passed to callback.
> *
> @@ -160,13 +161,20 @@ static int report_resume(struct pci_dev *dev, void *data)
> * If the device provided has no subordinate bus, call the provided
> * callback on the device itself.
> */
> -static void pci_walk_bridge(struct pci_dev *bridge, int (*cb)(struct pci_dev *, void *),
> +static void pci_walk_bridge(struct pci_dev *bridge, struct pci_dev *dev,
> + int (*cb)(struct pci_dev *, void *),
> void *userdata)
> {
> - if (bridge->subordinate)
> + /*
> + * In a non-native case where there is no OS-visible reporting
> + * device the bridge will be NULL, i.e., no RCEC, no PORT.
> + */
> + if (bridge && bridge->subordinate)
> pci_walk_bus(bridge->subordinate, cb, userdata);
> - else
> + else if (bridge)
> cb(bridge, userdata);
> + else
> + cb(dev, userdata);
> }
>
> static pci_ers_result_t flr_on_rciep(struct pci_dev *dev)
> @@ -196,16 +204,25 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> type = pci_pcie_type(dev);
> if (type == PCI_EXP_TYPE_ROOT_PORT ||
> type == PCI_EXP_TYPE_DOWNSTREAM ||
> - type == PCI_EXP_TYPE_RC_EC ||
> - type == PCI_EXP_TYPE_RC_END)
> + type == PCI_EXP_TYPE_RC_EC)
> bridge = dev;
> + else if (type == PCI_EXP_TYPE_RC_END)
> + bridge = dev->rcec;
> else
> bridge = pci_upstream_bridge(dev);
>
> pci_dbg(dev, "broadcast error_detected message\n");
> if (state == pci_channel_io_frozen) {
> - pci_walk_bridge(bridge, report_frozen_detected, &status);
> + pci_walk_bridge(bridge, dev, report_frozen_detected, &status);
> if (type == PCI_EXP_TYPE_RC_END) {
> + /*
> + * The callback only clears the Root Error Status
> + * of the RCEC (see aer.c). Only perform this for the
> + * native case, i.e., an RCEC is present.
> + */
> + if (bridge)
> + reset_subordinate_devices(bridge);
Help me understand this. There are lots of callbacks in this picture,
but I guess this "callback only clears Root Error Status" must refer
to aer_root_reset(), i.e., the reset_subordinate_devices pointer?
Of course, the caller of pcie_do_recovery() supplied that pointer.
And we can infer that it must be aer_root_reset(), not
dpc_reset_link(), because RCECs and RCiEPs are not allowed to
implement DPC.
I wish we didn't have either this assumption about what
reset_subordinate_devices points to, or the assumption about what
aer_root_reset() does. They both seem a little bit tenuous.
We already made aer_root_reset() smart enough to check for RCECs. Can
we put the FLR there, too? Then we wouldn't have this weird situation
where reset_subordinate_devices() does a reset and clears error
status, EXCEPT for this case where it only clears error status and we
do the reset here?
> status = flr_on_rciep(dev);
> if (status != PCI_ERS_RESULT_RECOVERED) {
> pci_warn(dev, "function level reset failed\n");
> @@ -219,13 +236,13 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> }
> }
> } else {
> - pci_walk_bridge(bridge, report_normal_detected, &status);
> + pci_walk_bridge(bridge, dev, report_normal_detected, &status);
> }
>
> if (status == PCI_ERS_RESULT_CAN_RECOVER) {
> status = PCI_ERS_RESULT_RECOVERED;
> pci_dbg(dev, "broadcast mmio_enabled message\n");
> - pci_walk_bridge(bridge, report_mmio_enabled, &status);
> + pci_walk_bridge(bridge, dev, report_mmio_enabled, &status);
> }
>
> if (status == PCI_ERS_RESULT_NEED_RESET) {
> @@ -236,14 +253,14 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> */
> status = PCI_ERS_RESULT_RECOVERED;
> pci_dbg(dev, "broadcast slot_reset message\n");
> - pci_walk_bridge(bridge, report_slot_reset, &status);
> + pci_walk_bridge(bridge, dev, report_slot_reset, &status);
> }
>
> if (status != PCI_ERS_RESULT_RECOVERED)
> goto failed;
>
> pci_dbg(dev, "broadcast resume message\n");
> - pci_walk_bridge(bridge, report_resume, &status);
> + pci_walk_bridge(bridge, dev, report_resume, &status);
>
> if (type == PCI_EXP_TYPE_ROOT_PORT ||
> type == PCI_EXP_TYPE_DOWNSTREAM ||
> --
> 2.28.0
>
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