linux-kernel - [PATCH v4 06/12] PCI: aardvark: Add FIXME comment for PCIE_CORE_CMD_STATUS

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Date:   Thu, 30 Apr 2020 10:06:19 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Jason Cooper <jason@...edaemon.net>, Andrew Lunn <andrew@...n.ch>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Andrew Murray <amurray@...goodpenguin.co.uk>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Remi Pommarel <repk@...plefau.lt>,
        Marek Behún <marek.behun@....cz>,
        Tomasz Maciej Nowak <tmn505@...il.com>,
        Xogium <contact@...ium.me>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org
Subject: [PATCH v4 06/12] PCI: aardvark: Add FIXME comment for PCIE_CORE_CMD_STATUS_REG access

This register is applicable only when the controller is configured for
Endpoint mode, which is not the case for the current version of this
driver.

Attempting to remove this code though caused some ath10k cards to stop
working, so for some unknown reason it is needed here.

This should be investigated and a comment explaining this should be put
before the code, so we add a FIXME comment for now.

Signed-off-by: Pali Rohár <pali@...nel.org>
---
 drivers/pci/controller/pci-aardvark.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
index 2ecc79c03ade..8332c71d69fa 100644
--- a/drivers/pci/controller/pci-aardvark.c
+++ b/drivers/pci/controller/pci-aardvark.c
@@ -439,6 +439,13 @@ static void advk_pcie_setup_hw(struct advk_pcie *pcie)
 
 	advk_pcie_train_link(pcie);
 
+	/*
+	 * FIXME: The following register update is suspicious. This register is
+	 * applicable only when the PCI controller is configured for Endpoint
+	 * mode, not as a Root Complex. But apparently when this code is
+	 * removed, some cards stop working. This should be investigated and
+	 * a comment explaining this should be put here.
+	 */
 	reg = advk_readl(pcie, PCIE_CORE_CMD_STATUS_REG);
 	reg |= PCIE_CORE_CMD_MEM_ACCESS_EN |
 		PCIE_CORE_CMD_IO_ACCESS_EN |
-- 
2.20.1