On Tue, Feb 05, 2019 at 12:17:41AM +0000, Trent Piepho wrote:
> This implements the workound described in the NXP IMX7d erratum e10728.
>
> Initial VCO oscillation may fail under corner conditions such as cold
> temperature. It causes PCIe PLL to fail to lock in the initialization
> phase, which results in the PCIe link failing to come up.
>
> The workaround is to disable Duty-cycle Corrector (DCC) calibration
> after G_RST.
>
> To do this it is necessary to gain access to the undocumented and
> currently unused PCIe PHY register bank. A new device tree node of type
> "fsl,imx7d-pcie-phy" is created for the PHY block and the existing PCIe
> device uses a phandle named "fsl,imx7d-pcie-phy" to point to it.
>
> Signed-off-by: Trent Piepho <tpiepho@xxxxxxxxxx>
> ---
> drivers/pci/controller/dwc/pci-imx6.c | 57 +++++++++++++++++++++++++++++++++++
> 1 file changed, 57 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 80f843030e36..06dd6aa927d4 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -18,6 +18,7 @@
> #include <linux/module.h>
> #include <linux/of_gpio.h>
> #include <linux/of_device.h>
> +#include <linux/of_address.h>
> #include <linux/pci.h>
> #include <linux/platform_device.h>
> #include <linux/regmap.h>
> @@ -61,6 +62,7 @@ struct imx6_pcie {
> u32 tx_swing_low;
> int link_gen;
> struct regulator *vpcie;
> + void __iomem *phy_base;
>
> /* power domain for pcie */
> struct device *pd_pcie;
> @@ -117,6 +119,23 @@ struct imx6_pcie {
> #define PCIE_PHY_RX_ASIC_OUT 0x100D
> #define PCIE_PHY_RX_ASIC_OUT_VALID (1 << 0)
>
> +/* iMX7 PCIe PHY registers */
> +#define PCIE_PHY_CMN_REG4 0x14
> +/* These are probably the bits that *aren't* DCC_FB_EN */
> +#define PCIE_PHY_CMN_REG4_DCC_FB_EN 0x29
> +
> +#define PCIE_PHY_CMN_REG15 0x54
> +#define PCIE_PHY_CMN_REG15_DLY_4 BIT(2)
> +#define PCIE_PHY_CMN_REG15_PLL_PD BIT(5)
> +#define PCIE_PHY_CMN_REG15_OVRD_PLL_PD BIT(7)
> +
> +#define PCIE_PHY_CMN_REG24 0x90
> +#define PCIE_PHY_CMN_REG24_RX_EQ BIT(6)
> +#define PCIE_PHY_CMN_REG24_RX_EQ_SEL BIT(3)
> +
> +#define PCIE_PHY_CMN_REG26 0x98
> +#define PCIE_PHY_CMN_REG26_ATT_MODE 0xBC
> +
> #define PHY_RX_OVRD_IN_LO 0x1005
> #define PHY_RX_OVRD_IN_LO_RX_DATA_EN (1 << 5)
> #define PHY_RX_OVRD_IN_LO_RX_PLL_EN (1 << 3)
> @@ -490,6 +509,26 @@ static void imx6_pcie_deassert_core_reset(struct imx6_pcie *imx6_pcie)
> switch (imx6_pcie->variant) {
> case IMX7D:
> reset_control_deassert(imx6_pcie->pciephy_reset);
> +
> + /* Workaround for ERR010728, failure of PCI-e PLL VCO to
> + * oscillate, especially when cold. This turns off "Duty-cycle
> + * Corrector" and other mysterious undocumented things.
> + */
> + if (likely(imx6_pcie->phy_base)) {
Nit: this is not a fast-path, so this branch performance is hardly
relevant.
> + /* De-assert DCC_FB_EN */
> + writel(PCIE_PHY_CMN_REG4_DCC_FB_EN,
> + imx6_pcie->phy_base + PCIE_PHY_CMN_REG4);
> + /* Assert RX_EQS and RX_EQS_SEL */
> + writel(PCIE_PHY_CMN_REG24_RX_EQ_SEL
> + | PCIE_PHY_CMN_REG24_RX_EQ,
> + imx6_pcie->phy_base + PCIE_PHY_CMN_REG24);
> + /* Assert ATT_MODE */
> + writel(PCIE_PHY_CMN_REG26_ATT_MODE,
> + imx6_pcie->phy_base + PCIE_PHY_CMN_REG26);
> + } else {
> + dev_warn(dev, "DT lacks imx7d-pcie-phy, unable to apply ERR010728 workaround\n");
It is a nit but the warning log is not necessarily true ie you may not
have a mapped address for other reasons as well. It is up to you but I
would change the log message.
Thanks,
Lorenzo
> + }
> +
> imx7d_pcie_wait_for_phy_pll_lock(imx6_pcie);
> break;
> case IMX6SX:
> @@ -919,6 +958,7 @@ static int imx6_pcie_probe(struct platform_device *pdev)
> struct device *dev = &pdev->dev;
> struct dw_pcie *pci;
> struct imx6_pcie *imx6_pcie;
> + struct device_node *np;
> struct resource *dbi_base;
> struct device_node *node = dev->of_node;
> int ret;
> @@ -939,6 +979,23 @@ static int imx6_pcie_probe(struct platform_device *pdev)
> imx6_pcie->variant =
> (enum imx6_pcie_variants)of_device_get_match_data(dev);
>
> + /* Find the PHY if one is defined, only imx7d uses it */
> + np = of_parse_phandle(node, "fsl,imx7d-pcie-phy", 0);
> + if (np) {
> + struct resource res;
> +
> + ret = of_address_to_resource(np, 0, &res);
> + if (ret) {
> + dev_err(dev, "Unable to map PCIe PHY\n");
> + return ret;
> + }
> + imx6_pcie->phy_base = devm_ioremap_resource(dev, &res);
> + if (IS_ERR(imx6_pcie->phy_base)) {
> + dev_err(dev, "Unable to map PCIe PHY\n");
> + return PTR_ERR(imx6_pcie->phy_base);
> + }
> + }
> +
> dbi_base = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> pci->dbi_base = devm_ioremap_resource(dev, dbi_base);
> if (IS_ERR(pci->dbi_base))
> --
> 2.14.4
>
