From a5fcec480f25eb5444c0b71ecdf9b18b09236b95 Mon Sep 17 00:00:00 2001 From: Tim Harvey Date: Tue, 19 Apr 2016 19:52:44 -0500 Subject: [PATCH] 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 Signed-off-by: Bjorn Helgaas Reviewed-by: Lucas Stach CC: Fabio Estevam CC: Zhu Richard CC: Akshay Bhat CC: Rob Herring CC: Shawn Guo --- .../bindings/pci/fsl,imx6q-pcie.txt | 4 ++++ drivers/pci/host/pci-imx6.c | 24 +++++++++++++------ 2 files changed, 21 insertions(+), 7 deletions(-) diff --git a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt index 636707df0952..d742f917505a 100644 --- a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt +++ b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt @@ -19,6 +19,10 @@ Optional properties: - fsl,tx-deemph-gen2-6db: Gen2 (6db) De-emphasis value. Default: 20 - fsl,tx-swing-full: Gen2 TX SWING FULL value. Default: 127 - fsl,tx-swing-low: TX launch amplitude swing_low value. Default: 127 +- fsl,max-link-speed: Specify PCI gen for link capability. Must be '2' for + gen2, otherwise will default to gen1. Note that the IMX6 LVDS clock outputs + do not meet gen2 jitter requirements and thus for gen2 capability a gen2 + compliant clock generator should be used and configured. - reset-gpio: Should specify the GPIO for controlling the PCI bus device reset signal. It's not polarity aware and defaults to active-low reset sequence (L=reset state, H=operation state). 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; -- 2.20.1