linux-kernel - [PATCH v2 2/2] PCI: pciehp: Clear the optional capabilities in DEVCTL2 on a hot-plug

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Date:   Tue, 18 Apr 2023 21:05:26 +0000
From:   Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
To:     <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     Bjorn Helgaas <bhelgaas@...gle.com>, <oohall@...il.com>,
        "Mahesh J Salgaonkar" <mahesh@...ux.ibm.com>,
        Lukas Wunner <lukas@...ner.de>,
        "Kuppuswamy Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Yazen Ghannam <yazen.ghannam@....com>,
        Fontenot Nathan <Nathan.Fontenot@....com>,
        "Smita Koralahalli" <Smita.KoralahalliChannabasappa@....com>
Subject: [PATCH v2 2/2] PCI: pciehp: Clear the optional capabilities in DEVCTL2 on a hot-plug

Clear all capabilities in Device Control 2 register as they are optional
and it is not determined whether the next device inserted will support
these capabilities. Moreover, Section 6.13 of the PCIe Base
Specification [1], recommends clearing the ARI Forwarding Enable bit on
a hot-plug event as its not guaranteed that the newly added component
is in fact an ARI device.

[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@....com>
---
v2:
	Clear all optional capabilities in Device Control 2 register
	instead of individually clearing ARI Forwarding Enable,
	AtomicOp Requestor Enable and 10-bit Tag Requestor Enable.
---
 drivers/pci/hotplug/pciehp_pci.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/pci/hotplug/pciehp_pci.c b/drivers/pci/hotplug/pciehp_pci.c
index d17f3bf36f70..aabf7884ff30 100644
--- a/drivers/pci/hotplug/pciehp_pci.c
+++ b/drivers/pci/hotplug/pciehp_pci.c
@@ -104,6 +104,7 @@ void pciehp_unconfigure_device(struct controller *ctrl, bool presence)
 	list_for_each_entry_safe_reverse(dev, temp, &parent->devices,
 					 bus_list) {
 		pci_dev_get(dev);
+		pcie_capability_clear_word(dev, PCI_EXP_DEVCTL2, 0xffff);
 		pci_stop_and_remove_bus_device(dev);
 		/*
 		 * Ensure that no new Requests will be generated from
-- 
2.17.1