linux-kernel - [PATCH 5/8] PCI/DPC: Converge EDR and DPC Path of clearing AER registers

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Date:   Mon,  4 Oct 2021 19:22:40 +0530
From:   Naveen Naidu <naveennaidu479@...il.com>
To:     bhelgaas@...gle.com, ruscur@...sell.cc, oohall@...il.com
Cc:     Naveen Naidu <naveennaidu479@...il.com>,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        skhan@...uxfoundation.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH 5/8] PCI/DPC: Converge EDR and DPC Path of clearing AER registers

In the EDR path, AER registers are cleared *after* DPC error event is
processed. The process stack in EDR is:

  edr_handle_event()
    dpc_process_error()
    pci_aer_raw_clear_status()
    pcie_do_recovery()

But in DPC path, AER status registers are cleared *while* processing
the error. The process stack in DPC is:

  dpc_handler()
    dpc_process_error()
      pci_aer_clear_status()
    pcie_do_recovery()

In EDR path, AER status registers are cleared irrespective of whether
the error was an RP PIO or unmasked uncorrectable error. But in DPC, the
AER status registers are cleared only when it's an unmasked uncorrectable
error.

This leads to two different behaviours for the same task (handling of
DPC errors) in FFS systems and when native OS has control.

Bring the same semantics for clearing the AER status register in EDR
path and DPC path.

Signed-off-by: Naveen Naidu <naveennaidu479@...il.com>
---
 drivers/pci/pcie/dpc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
index faf4a1e77fab..68899a3db126 100644
--- a/drivers/pci/pcie/dpc.c
+++ b/drivers/pci/pcie/dpc.c
@@ -288,7 +288,6 @@ void dpc_process_error(struct pci_dev *pdev)
 		 dpc_get_aer_uncorrect_severity(pdev, &info) &&
 		 aer_get_device_error_info(pdev, &info)) {
 		aer_print_error(pdev, &info);
-		pci_aer_clear_status(pdev);
 	}
 }

@@ -297,6 +296,7 @@ static irqreturn_t dpc_handler(int irq, void *context)
 	struct pci_dev *pdev = context;

 	dpc_process_error(pdev);
+	pci_aer_clear_status(pdev);

 	/* We configure DPC so it only triggers on ERR_FATAL */
 	pcie_do_recovery(pdev, pci_channel_io_frozen, dpc_reset_link);
-- 
2.25.1