| Message ID | 20230815212043.114913-2-Smita.KoralahalliChannabasappa@amd.com (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
| Series | PCI: pciehp: Add support for native AER and DPC handling on async remove | expand |
On Tue, Aug 15, 2023 at 09:20:41PM +0000, Smita Koralahalli wrote: > According to PCIe r6.0 sec 6.7.6 [1], async removal with DPC may result in > surprise down error. This error is expected and is just a side-effect of > async remove. > > Add support to handle the surprise down error generated as a side-effect > of async remove. Typically, this error is benign as the pciehp handler > invoked by PDC or/and DLLSC alongside DPC, de-enumerates and brings down > the device appropriately. But the error messages might confuse users. Get > rid of these irritating log messages with a 1s delay while pciehp waits > for dpc recovery. [...] > Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com> Reviewed-by: Lukas Wunner <lukas@wunner.de> The subject is slightly inaccurate as this doesn't touch pciehp source files, although it is *related* to pciehp. As an example, a perhaps more accurate subject might be something like... PCI/DPC: Ignore Surprise Down errors on hot removal ...but I don't think it's necessary to respin just for that as Bjorn is probably able to adjust the subject to his liking when applying the patch. Thanks a lot for patiently pursuing this issue, good to see it fixed. Five years ago there was an attempt to solve it through masking Surprise Down errors, which you've verified to not be a viable approach: https://patchwork.kernel.org/project/linux-pci/patch/20180818065126.77912-2-okaya@kernel.org/ Lukas
On 8/28/2023 12:35 AM, Lukas Wunner wrote: > On Tue, Aug 15, 2023 at 09:20:41PM +0000, Smita Koralahalli wrote: >> According to PCIe r6.0 sec 6.7.6 [1], async removal with DPC may result in >> surprise down error. This error is expected and is just a side-effect of >> async remove. >> >> Add support to handle the surprise down error generated as a side-effect >> of async remove. Typically, this error is benign as the pciehp handler >> invoked by PDC or/and DLLSC alongside DPC, de-enumerates and brings down >> the device appropriately. But the error messages might confuse users. Get >> rid of these irritating log messages with a 1s delay while pciehp waits >> for dpc recovery. > [...] >> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com> > > Reviewed-by: Lukas Wunner <lukas@wunner.de> > > The subject is slightly inaccurate as this doesn't touch pciehp source > files, although it is *related* to pciehp. > > As an example, a perhaps more accurate subject might be something like... > > PCI/DPC: Ignore Surprise Down errors on hot removal > > ...but I don't think it's necessary to respin just for that as Bjorn is > probably able to adjust the subject to his liking when applying the patch. > > Thanks a lot for patiently pursuing this issue, good to see it fixed. > > Five years ago there was an attempt to solve it through masking Surprise > Down errors, which you've verified to not be a viable approach: > > https://patchwork.kernel.org/project/linux-pci/patch/20180818065126.77912-2-okaya@kernel.org/ > > Lukas Thanks for the review. Would it be possible to consider this patch as a standalone while I work on 10-bit tags enumeration? I can do v5 for this patch with $SUBJECT changes and also include clearing Atomic Ops and 10-bit tags unconditionally on hot-remove if that works.. Thanks, Smita
On Tue, Sep 12, 2023 at 03:45:34PM -0700, Smita Koralahalli wrote: > Thanks for the review. Would it be possible to consider this patch as a > standalone while I work on 10-bit tags enumeration? I can do v5 for this > patch with $SUBJECT changes and also include clearing Atomic Ops and 10-bit > tags unconditionally on hot-remove if that works.. Right, this patch is still in state "New" in patchwork: https://patchwork.kernel.org/project/linux-pci/patch/20230815212043.114913-2-Smita.KoralahalliChannabasappa@amd.com/ Which means Bjorn probably hasn't gotten a chance to look at it. Indeed it can be applied standalone if Bjorn gets to it this cycle and doesn't have any objections. Feel free to include my Reviewed-by tag if/when resending. Thanks, Lukas
diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c index 3ceed8e3de41..25e9ddeeb271 100644 --- a/drivers/pci/pcie/dpc.c +++ b/drivers/pci/pcie/dpc.c @@ -292,10 +292,79 @@ void dpc_process_error(struct pci_dev *pdev) } } +static void pci_clear_surpdn_errors(struct pci_dev *pdev) +{ + u16 reg16; + u32 reg32; + + if (pdev->dpc_rp_extensions) { + pci_read_config_dword(pdev, pdev->dpc_cap + PCI_EXP_DPC_RP_PIO_STATUS, + ®32); + pci_write_config_dword(pdev, pdev->dpc_cap + PCI_EXP_DPC_RP_PIO_STATUS, + reg32); + } + + /* + * In practice, Surprise Down errors have been observed to also set + * error bits in the Status Register as well as the Fatal Error + * Detected bit in the Device Status Register. + */ + pci_read_config_word(pdev, PCI_STATUS, ®16); + pci_write_config_word(pdev, PCI_STATUS, reg16); + + pcie_capability_write_word(pdev, PCI_EXP_DEVSTA, PCI_EXP_DEVSTA_FED); +} + +static void dpc_handle_surprise_removal(struct pci_dev *pdev) +{ + if (!pcie_wait_for_link(pdev, false)) { + pci_info(pdev, "Data Link Layer Link Active not cleared in 1000 msec\n"); + goto out; + } + + if (pdev->dpc_rp_extensions && dpc_wait_rp_inactive(pdev)) + goto out; + + pci_aer_raw_clear_status(pdev); + pci_clear_surpdn_errors(pdev); + + pci_write_config_word(pdev, pdev->dpc_cap + PCI_EXP_DPC_STATUS, + PCI_EXP_DPC_STATUS_TRIGGER); + +out: + clear_bit(PCI_DPC_RECOVERED, &pdev->priv_flags); + wake_up_all(&dpc_completed_waitqueue); +} + +static bool dpc_is_surprise_removal(struct pci_dev *pdev) +{ + u16 status; + + if (!pdev->is_hotplug_bridge) + return false; + + pci_read_config_word(pdev, pdev->aer_cap + PCI_ERR_UNCOR_STATUS, + &status); + + if (!(status & PCI_ERR_UNC_SURPDN)) + return false; + + return true; +} + static irqreturn_t dpc_handler(int irq, void *context) { struct pci_dev *pdev = context; + /* + * According to PCIe r6.0 sec 6.7.6, errors are an expected side effect + * of async removal and should be ignored by software. + */ + if (dpc_is_surprise_removal(pdev)) { + dpc_handle_surprise_removal(pdev); + return IRQ_HANDLED; + } + dpc_process_error(pdev); /* We configure DPC so it only triggers on ERR_FATAL */
According to PCIe r6.0 sec 6.7.6 [1], async removal with DPC may result in surprise down error. This error is expected and is just a side-effect of async remove. Add support to handle the surprise down error generated as a side-effect of async remove. Typically, this error is benign as the pciehp handler invoked by PDC or/and DLLSC alongside DPC, de-enumerates and brings down the device appropriately. But the error messages might confuse users. Get rid of these irritating log messages with a 1s delay while pciehp waits for dpc recovery. The implementation is as follows: On an async remove a DPC is triggered along with a Presence Detect State change and/or DLL State Change. Determine it's an async remove by checking for DPC Trigger Status in DPC Status Register and Surprise Down Error Status in AER Uncorrected Error Status to be non-zero. If true, treat the DPC event as a side-effect of async remove, clear the error status registers and continue with hot-plug tear down routines. If not, follow the existing routine to handle AER and DPC errors. Please note that, masking Surprise Down Errors was explored as an alternative approach, but left due to the odd behavior that masking only avoids the interrupt, but still records an error per PCIe r6.0.1 Section 6.2.3.2.2. That stale error is going to be reported the next time some error other than Surprise Down is handled. Dmesg before: pcieport 0000:00:01.4: DPC: containment event, status:0x1f01 source:0x0000 pcieport 0000:00:01.4: DPC: unmasked uncorrectable error detected pcieport 0000:00:01.4: PCIe Bus Error: severity=Uncorrected (Fatal), type=Transaction Layer, (Receiver ID) pcieport 0000:00:01.4: device [1022:14ab] error status/mask=00000020/04004000 pcieport 0000:00:01.4: [ 5] SDES (First) nvme nvme2: frozen state error detected, reset controller pcieport 0000:00:01.4: DPC: Data Link Layer Link Active not set in 1000 msec pcieport 0000:00:01.4: AER: subordinate device reset failed pcieport 0000:00:01.4: AER: device recovery failed pcieport 0000:00:01.4: pciehp: Slot(16): Link Down nvme2n1: detected capacity change from 1953525168 to 0 pci 0000:04:00.0: Removing from iommu group 49 Dmesg after: pcieport 0000:00:01.4: pciehp: Slot(16): Link Down nvme1n1: detected capacity change from 1953525168 to 0 pci 0000:04:00.0: Removing from iommu group 37 [1] PCI Express Base Specification Revision 6.0, Dec 16 2021. https://members.pcisig.com/wg/PCI-SIG/document/16609 Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com> --- v2: Indentation is taken care. (Bjorn) Unrelevant dmesg logs are removed. (Bjorn) Rephrased commit message, to be clear on native vs FW-First handling. (Bjorn and Sathyanarayanan) Prefix changed from pciehp_ to dpc_. (Lukas) Clearing ARI and AtomicOp Requester are performed as a part of (de-)enumeration in pciehp_unconfigure_device(). (Lukas) Changed to clearing all optional capabilities in DEVCTL2. OS-First -> native. (Sathyanarayanan) v3: Added error message when root port become inactive. Modified commit description to add more details. Rearranged code comments and function calls with no functional change. Additional check for is_hotplug_bridge. dpc_completed_waitqueue to wakeup pciehp handler. Cleared only Fatal error detected in DEVSTA. v4: Made read+write conditional on "if (pdev->dpc_rp_extensions)" for DPC_RP_PIO_STATUS. Wrapped to 80 chars. Code comment for clearing PCI_STATUS and PCI_EXP_DEVSTA. Added pcie_wait_for_link() check. Removed error message for root port inactive as the message already existed. Check for is_hotplug_bridge before registers read. Section 6.7.6 of the PCIe Base Spec 6.0 -> PCIe r6.0 sec 6.7.6. Made code comment more meaningful. --- drivers/pci/pcie/dpc.c | 69 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 69 insertions(+)