linux-kernel - [PATCH v3 7/8] PCI/ERR: Remove redundant clearing of AER register in pcie_do

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Date:   Mon,  4 Oct 2021 20:00:03 +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,
        linux-pci@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v3 7/8] PCI/ERR: Remove redundant clearing of AER register in pcie_do_recovery()

pcie_do_recovery() is shared across the following paths:
 - ACPI APEI
 - Native AER path
 - EDR
 - DPC

ACPI APEI
==========

  ghes_handle_aer()
    aer_recover_queue()
      kfifo_in_spinlocked(aer_recover_ring)

  aer_recover_work_func()
    while (kfifo_get(aer_recover_ring))
      pcie_do_recovery()

In this path the system firmware clears the AER registers before
handing off the record to the OS in ghes_handle_aer()

Native AER
==========

 aer_irq()
   aer_add_err_devices_to_queue()
     kfifo_put(&rpc->aer_fifo, *e_dev)
     clear_error_source_aer_registers()   <---- AER registers are cleard

 aer_isr()
   aer_isr_one_error()
    handle_error_source()
      pcie_do_recovery()

The AER registers are cleared during the handling of IRQ, i.e before we
the recovery starts.

DPC
=====

  dpc_handler()
    dpc_process_error()
    pci_aer_clear_status()       <---- AER registers are cleared
    pcie_do_recovery()

EDR
====

  edr_handle_event()
    dpc_process_error()
    pci_aer_raw_clear_status()  <---- AER registers are cleared
    pcie_do_recovery()

In all the above paths, the AER registers are cleared before
pcie_do_recovery(). The non fatal status AER registers are again cleared
in pcie_do_recovery(). This is redundant.

Remove redundant clearing of AER register in pcie_do_recovery()

Signed-off-by: Naveen Naidu <naveennaidu479@...il.com>
---
 drivers/pci/pcie/err.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
index b576aa890c76..fe04b0ae22f4 100644
--- a/drivers/pci/pcie/err.c
+++ b/drivers/pci/pcie/err.c
@@ -231,14 +231,11 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
 
 	/*
 	 * If we have native control of AER, clear error status in the device
-	 * that detected the error.  If the platform retained control of AER,
-	 * it is responsible for clearing this status.  In that case, the
-	 * signaling device may not even be visible to the OS.
+	 * that detected the error.
 	 */
-	if (host->native_aer || pcie_ports_native) {
+	if (host->native_aer || pcie_ports_native)
 		pcie_clear_device_status(dev);
-		pci_aer_clear_nonfatal_status(dev);
-	}
+
 	pci_info(bridge, "device recovery successful\n");
 	return status;
 
-- 
2.25.1