linux-kernel - [PATCH] PCI: amlogic: meson: Don't use FAST_LINK

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Message-Id: <20200429164230.309922-1-maz@kernel.org>
Date:   Wed, 29 Apr 2020 17:42:30 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     linux-pci@...r.kernel.org, linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Yue Wang <yue.wang@...ogic.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Kevin Hilman <khilman@...libre.com>
Subject: [PATCH] PCI: amlogic: meson: Don't use FAST_LINK_MODE to set up link

My vim3l board stubbornly refuses to play ball with a bog
standard PCIe switch (ASM1184e), spitting all kind of errors
ranging from link never coming up to crazy things like downstream
ports falling off the face of the planet.

Upon investigating how the PCIe RC is configured, I found the
following nugget: the Sysnopsys DWC PCIe Reference Manual, in the
section dedicated to the PLCR register, describes bit 7 (FAST_LINK_MODE)
as:

"Sets all internal timers to fast mode for simulation purposes."

I completely understand the need for setting this bit from a simulation
perspective, but what I have on my desk is actual silicon, which
expects timers to have a nominal value (and I expect this is the
case for most people).

Making sure the FAST_LINK_MODE bit is cleared when configuring the RC
solves this problem.

Fixes: 9c0ef6d34fdb ("PCI: amlogic: Add the Amlogic Meson PCIe controller driver")
Signed-off-by: Marc Zyngier <maz@...nel.org>
---
 drivers/pci/controller/dwc/pci-meson.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/dwc/pci-meson.c b/drivers/pci/controller/dwc/pci-meson.c
index 3715dceca1bf..ca59ba9e0ecd 100644
--- a/drivers/pci/controller/dwc/pci-meson.c
+++ b/drivers/pci/controller/dwc/pci-meson.c
@@ -289,11 +289,11 @@ static void meson_pcie_init_dw(struct meson_pcie *mp)
 	meson_cfg_writel(mp, val, PCIE_CFG0);
 
 	val = meson_elb_readl(mp, PCIE_PORT_LINK_CTRL_OFF);
-	val &= ~LINK_CAPABLE_MASK;
+	val &= ~(LINK_CAPABLE_MASK | FAST_LINK_MODE);
 	meson_elb_writel(mp, val, PCIE_PORT_LINK_CTRL_OFF);
 
 	val = meson_elb_readl(mp, PCIE_PORT_LINK_CTRL_OFF);
-	val |= LINK_CAPABLE_X1 | FAST_LINK_MODE;
+	val |= LINK_CAPABLE_X1;
 	meson_elb_writel(mp, val, PCIE_PORT_LINK_CTRL_OFF);
 
 	val = meson_elb_readl(mp, PCIE_GEN2_CTRL_OFF);
-- 
2.26.2