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authorTim Harvey <tharvey@gateworks.com>2016-04-19 19:52:44 -0500
committerBjorn Helgaas <bhelgaas@google.com>2016-04-19 19:52:44 -0500
commita5fcec480f25eb5444c0b71ecdf9b18b09236b95 (patch)
treed7922086b065ff22027531b280fe146f769c5150 /drivers/pci
parent3ea8529acc30467331b7b1f5da6cf668fac091c7 (diff)
downloadlinux-a5fcec480f25eb5444c0b71ecdf9b18b09236b95.tar.bz2
PCI: imx6: Add DT property for link gen, default to Gen1
Freescale has stated [1] that the LVDS clock source of the IMX6 does not pass the PCI Gen2 clock jitter test, therefore unless an external Gen2 compliant external clock source is present and supplied back to the IMX6 PCIe core via LVDS CLK1/CLK2 you can not claim Gen2 compliance. Add a DT property to specify Gen1 vs Gen2 and check this before allowing a Gen2 link. We default to Gen1 if the property is not present because at this time there are no IMX6 boards in mainline that 'input' a clock on LVDS CLK1/CLK2. In order to be Gen2 compliant on IMX6 you need to: - Have a Gen2 compliant external clock generator and route that clock back to either LVDS CLK1 or LVDS CLK2 as an input (see IMX6SX-SabreSD reference design). - Specify this clock in the PCIe node in the DT (i.e., IMX6QDL_CLK_LVDS1_IN or IMX6QDL_CLK_LVDS2_IN instead of IMX6QDL_CLK_LVDS1_GATE which configures it as a CLK output). [1] https://community.freescale.com/message/453209 Signed-off-by: Tim Harvey <tharvey@gateworks.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Lucas Stach <l.stach@pengutronix.de> CC: Fabio Estevam <fabio.estevam@freescale.com> CC: Zhu Richard <Richard.Zhu@freescale.com> CC: Akshay Bhat <akshay.bhat@timesys.com> CC: Rob Herring <robh+dt@kernel.org> CC: Shawn Guo <shawnguo@kernel.org>
Diffstat (limited to 'drivers/pci')
-rw-r--r--drivers/pci/host/pci-imx6.c24
1 files changed, 17 insertions, 7 deletions
diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
index 0b8793d908de..837d5e0447ac 100644
--- a/drivers/pci/host/pci-imx6.c
+++ b/drivers/pci/host/pci-imx6.c
@@ -47,6 +47,7 @@ struct imx6_pcie {
u32 tx_deemph_gen2_6db;
u32 tx_swing_full;
u32 tx_swing_low;
+ int link_gen;
};
/* PCIe Root Complex registers (memory-mapped) */
@@ -471,11 +472,15 @@ static int imx6_pcie_establish_link(struct pcie_port *pp)
goto err_reset_phy;
}
- /* Allow Gen2 mode after the link is up. */
- tmp = readl(pp->dbi_base + PCIE_RC_LCR);
- tmp &= ~PCIE_RC_LCR_MAX_LINK_SPEEDS_MASK;
- tmp |= PCIE_RC_LCR_MAX_LINK_SPEEDS_GEN2;
- writel(tmp, pp->dbi_base + PCIE_RC_LCR);
+ if (imx6_pcie->link_gen == 2) {
+ /* Allow Gen2 mode after the link is up. */
+ tmp = readl(pp->dbi_base + PCIE_RC_LCR);
+ tmp &= ~PCIE_RC_LCR_MAX_LINK_SPEEDS_MASK;
+ tmp |= PCIE_RC_LCR_MAX_LINK_SPEEDS_GEN2;
+ writel(tmp, pp->dbi_base + PCIE_RC_LCR);
+ } else {
+ dev_info(pp->dev, "Link: Gen2 disabled\n");
+ }
/*
* Start Directed Speed Change so the best possible speed both link
@@ -499,8 +504,7 @@ static int imx6_pcie_establish_link(struct pcie_port *pp)
}
tmp = readl(pp->dbi_base + PCIE_RC_LCSR);
- dev_dbg(pp->dev, "Link up, Gen=%i\n", (tmp >> 16) & 0xf);
-
+ dev_info(pp->dev, "Link up, Gen%i\n", (tmp >> 16) & 0xf);
return 0;
err_reset_phy:
@@ -678,6 +682,12 @@ static int __init imx6_pcie_probe(struct platform_device *pdev)
&imx6_pcie->tx_swing_low))
imx6_pcie->tx_swing_low = 127;
+ /* Limit link speed */
+ ret = of_property_read_u32(pp->dev->of_node, "fsl,max-link-speed",
+ &imx6_pcie->link_gen);
+ if (ret)
+ imx6_pcie->link_gen = 1;
+
ret = imx6_add_pcie_port(pp, pdev);
if (ret < 0)
return ret;