Subject: [PATCH v2 22/23] PCI: aardvark: Update comment about link going down after link-up

From: Marek Behún <[email-masked]>
Date: Mon, 10 Jan 2022 02:50:17 +0100

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.

Signed-off-by: Marek Behún <[email-masked]>
---
 drivers/pci/controller/pci-aardvark.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
index 360e2e3b3aa6..2c5cc929b94f 100644
--- a/drivers/pci/controller/pci-aardvark.c
+++ b/drivers/pci/controller/pci-aardvark.c
@@ -1007,8 +1007,12 @@ static bool advk_pcie_valid_device(struct advk_pcie *pcie, struct pci_bus *bus,
 		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;
-- 
2.34.1

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