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From: "Pali Rohár" <pali@kernel.org>
To: "Jason Cooper" <jason@lakedaemon.net>,
	"Andrew Lunn" <andrew@lunn.ch>,
	"Gregory Clement" <gregory.clement@bootlin.com>,
	"Sebastian Hesselbarth" <sebastian.hesselbarth@gmail.com>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Thomas Petazzoni" <thomas.petazzoni@bootlin.com>,
	"Lorenzo Pieralisi" <lorenzo.pieralisi@arm.com>,
	"Andrew Murray" <amurray@thegoodpenguin.co.uk>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Remi Pommarel" <repk@triplefau.lt>,
	"Marek Behún" <marek.behun@nic.cz>,
	"Tomasz Maciej Nowak" <tmn505@gmail.com>,
	Xogium <contact@xogium.me>
Cc: devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-pci@vger.kernel.org
Subject: [PATCH v4 02/12] PCI: aardvark: Don't blindly enable ASPM L0s and don't write to read-only register
Date: Thu, 30 Apr 2020 10:06:15 +0200
Message-ID: <20200430080625.26070-3-pali@kernel.org> (raw)
In-Reply-To: <20200430080625.26070-1-pali@kernel.org>

Trying to change Link Status register does not have any effect as this
is a read-only register. Trying to overwrite bits for Negotiated Link
Width does not make sense.

In future proper change of link width can be done via Lane Count Select
bits in PCIe Control 0 register.

Trying to unconditionally enable ASPM L0s via ASPM Control bits in Link
Control register is wrong. There should be at least some detection if
endpoint supports L0s as isn't mandatory.

Moreover ASPM Control bits in Link Control register are controlled by
pcie/aspm.c code which sets it according to system ASPM settings,
immediately after aardvark driver probes. So setting these bits by
aardvark driver has no long running effect.

Remove code which touches ASPM L0s bits from this driver and let
kernel's ASPM implementation to set ASPM state properly.

Some users are reporting issues that this code is problematic for some
Intel wifi cards and removing it fixes them, see e.g.:
https://bugzilla.kernel.org/show_bug.cgi?id=196339

If problems with Intel wifi cards occur even after this commit, then
pcie/aspm.c code could be modified / hooked to not enable ASPM L0s state
for affected problematic cards.

Signed-off-by: Pali Rohár <pali@kernel.org>
---
 drivers/pci/controller/pci-aardvark.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
index f9955b494267..74b90940a9d4 100644
--- a/drivers/pci/controller/pci-aardvark.c
+++ b/drivers/pci/controller/pci-aardvark.c
@@ -356,10 +356,6 @@ static void advk_pcie_setup_hw(struct advk_pcie *pcie)
 
 	advk_pcie_wait_for_link(pcie);
 
-	reg = PCIE_CORE_LINK_L0S_ENTRY |
-		(1 << PCIE_CORE_LINK_WIDTH_SHIFT);
-	advk_writel(pcie, reg, PCIE_CORE_LINK_CTRL_STAT_REG);
-
 	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


  parent reply index

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-30  8:06 [PATCH v4 00/12] PCI: aardvark: Fix support for Turris MOX and Compex wifi cards Pali Rohár
2020-04-30  8:06 ` [PATCH v4 01/12] PCI: aardvark: Train link immediately after enabling training Pali Rohár
2020-05-04 15:50   ` Bjorn Helgaas
2020-05-07 21:05   ` Rob Herring
2020-04-30  8:06 ` Pali Rohár [this message]
2020-05-07 21:07   ` [PATCH v4 02/12] PCI: aardvark: Don't blindly enable ASPM L0s and don't write to read-only register Rob Herring
2020-04-30  8:06 ` [PATCH v4 03/12] PCI: of: Zero max-link-speed value is invalid Pali Rohár
2020-05-07 21:07   ` Rob Herring
2020-04-30  8:06 ` [PATCH v4 04/12] PCI: aardvark: Improve link training Pali Rohár
2020-05-07 21:10   ` Rob Herring
2020-04-30  8:06 ` [PATCH v4 05/12] PCI: aardvark: Issue PERST via GPIO Pali Rohár
2020-04-30  8:22   ` Pali Rohár
2020-05-07 21:20     ` Rob Herring
2020-04-30  8:06 ` [PATCH v4 06/12] PCI: aardvark: Add FIXME comment for PCIE_CORE_CMD_STATUS_REG access Pali Rohár
2020-05-07 21:20   ` Rob Herring
2020-04-30  8:06 ` [PATCH v4 07/12] PCI: aardvark: Add PHY support Pali Rohár
2020-05-07 21:23   ` Rob Herring
2020-04-30  8:06 ` [PATCH v4 08/12] PCI: aardvark: Replace custom macros by standard linux/pci_regs.h macros Pali Rohár
2020-05-04 15:52   ` Bjorn Helgaas
2020-05-07 21:24   ` Rob Herring
2020-04-30  8:06 ` [PATCH v4 09/12] dt-bindings: PCI: aardvark: Describe new properties Pali Rohár
2020-05-07 21:25   ` Rob Herring
2020-04-30  8:06 ` [PATCH v4 10/12] arm64: dts: marvell: armada-37xx: Set pcie_reset_pin to gpio function Pali Rohár
2020-04-30  8:06 ` [PATCH v4 11/12] arm64: dts: marvell: armada-37xx: Move PCIe comphy handle property Pali Rohár
2020-04-30  8:06 ` [PATCH v4 12/12] arm64: dts: marvell: armada-37xx: Move PCIe max-link-speed property Pali Rohár
2020-05-04 15:50   ` Bjorn Helgaas
2020-05-08 13:11 ` [PATCH v4 00/12] PCI: aardvark: Fix support for Turris MOX and Compex wifi cards Tomasz Maciej Nowak
2020-05-13 11:16 ` Pali Rohár
2020-05-13 11:33   ` Lorenzo Pieralisi
2020-05-13 11:59     ` Pali Rohár
2020-05-13 11:56 ` Thomas Petazzoni
2020-05-17 15:57   ` Gregory CLEMENT
2020-05-18 10:30     ` Pali Rohár
2020-05-18 13:46       ` Lorenzo Pieralisi
2020-05-18 13:50         ` Marek Behun

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