linux-kernel - [PATCH 5.17 140/140] PCI: aardvark: Update comment about link going down after link-up

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Date:   Tue, 10 May 2022 15:08:50 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, pali@...nel.org,
        Marek Behún <kabel@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Subject: [PATCH 5.17 140/140] PCI: aardvark: Update comment about link going down after link-up

From: "Marek Behún" <kabel@...nel.org>

commit 92f4ffecc4170ce29e67a1f8d51c168c3de95fb2 upstream.

Update the comment about what happens when link goes down after we have
checked for link-up. If a PIO request is done while link-down, we have
a serious problem.

Link: https://lore.kernel.org/r/20220110015018.26359-23-kabel@kernel.org
Signed-off-by: Marek Behún <kabel@...nel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/pci/controller/pci-aardvark.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/drivers/pci/controller/pci-aardvark.c
+++ b/drivers/pci/controller/pci-aardvark.c
@@ -998,8 +998,12 @@ static bool advk_pcie_valid_device(struc
 		return false;
 
 	/*
-	 * If the link goes down after we check for link-up, nothing bad
-	 * happens but the config access times out.
+	 * If the link goes down after we check for link-up, we have a problem:
+	 * if a PIO request is executed while link-down, the whole controller
+	 * gets stuck in a non-functional state, and even after link comes up
+	 * again, PIO requests won't work anymore, and a reset of the whole PCIe
+	 * controller is needed. Therefore we need to prevent sending PIO
+	 * requests while the link is down.
 	 */
 	if (!pci_is_root_bus(bus) && !advk_pcie_link_up(pcie))
 		return false;