[PATCH v3 2/2] PCI: imx: Initial imx7d pm support

[Leonard Crestez]

On imx7d the pcie-phy power domain is turned off in suspend and this can
make the system hang after resume when attempting any read from PCI.

Fix this by adding minimal suspend/resume code from the nxp internal
tree. This will prepare for powering down on suspend and reset the block
on resume.

Code is only for imx7d but a very similar sequence can be used for
other socs.

The original author is mostly Richard Zhu <hongxing.zhu@xxxxxxx>, this
patch adjusts the code to the upstream imx7d implemention using reset
controls and power domains.

Signed-off-by: Leonard Crestez <leonard.crestez@xxxxxxx>
---
 drivers/pci/controller/dwc/pci-imx6.c | 97 +++++++++++++++++++++++++--
 1 file changed, 92 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index 4a9a673b4777..65b6d1015723 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -540,10 +540,28 @@ static int imx6_pcie_wait_for_speed_change(struct imx6_pcie *imx6_pcie)
 
 	dev_err(dev, "Speed change timeout\n");
 	return -EINVAL;
 }
 
+static void imx6_pcie_ltssm_enable(struct device *dev)
+{
+	struct imx6_pcie *imx6_pcie = dev_get_drvdata(dev);
+
+	switch (imx6_pcie->variant) {
+	case IMX6Q:
+	case IMX6SX:
+	case IMX6QP:
+		regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
+				   IMX6Q_GPR12_PCIE_CTL_2,
+				   IMX6Q_GPR12_PCIE_CTL_2);
+		break;
+	case IMX7D:
+		reset_control_deassert(imx6_pcie->apps_reset);
+		break;
+	}
+}
+
 static int imx6_pcie_establish_link(struct imx6_pcie *imx6_pcie)
 {
 	struct dw_pcie *pci = imx6_pcie->pci;
 	struct device *dev = pci->dev;
 	u32 tmp;
@@ -558,15 +576,11 @@ static int imx6_pcie_establish_link(struct imx6_pcie *imx6_pcie)
 	tmp &= ~PCIE_RC_LCR_MAX_LINK_SPEEDS_MASK;
 	tmp |= PCIE_RC_LCR_MAX_LINK_SPEEDS_GEN1;
 	dw_pcie_writel_dbi(pci, PCIE_RC_LCR, tmp);
 
 	/* Start LTSSM. */
-	if (imx6_pcie->variant == IMX7D)
-		reset_control_deassert(imx6_pcie->apps_reset);
-	else
-		regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
-				   IMX6Q_GPR12_PCIE_CTL_2, 1 << 10);
+	imx6_pcie_ltssm_enable(dev);
 
 	ret = imx6_pcie_wait_for_link(imx6_pcie);
 	if (ret)
 		goto err_reset_phy;
 
@@ -680,10 +694,82 @@ static int imx6_add_pcie_port(struct imx6_pcie *imx6_pcie,
 
 static const struct dw_pcie_ops dw_pcie_ops = {
 	.link_up = imx6_pcie_link_up,
 };
 
+#ifdef CONFIG_PM_SLEEP
+static void imx6_pcie_ltssm_disable(struct device *dev)
+{
+	struct imx6_pcie *imx6_pcie = dev_get_drvdata(dev);
+
+	switch (imx6_pcie->variant) {
+	case IMX6SX:
+	case IMX6QP:
+		regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
+				   IMX6Q_GPR12_PCIE_CTL_2, 0);
+		break;
+	case IMX7D:
+		reset_control_assert(imx6_pcie->apps_reset);
+		break;
+	default:
+		dev_err(dev, "ltssm_disable not supported\n");
+	}
+}
+
+static void imx6_pcie_clk_disable(struct imx6_pcie *imx6_pcie)
+{
+	clk_disable_unprepare(imx6_pcie->pcie);
+	clk_disable_unprepare(imx6_pcie->pcie_phy);
+	clk_disable_unprepare(imx6_pcie->pcie_bus);
+
+	if (imx6_pcie->variant == IMX7D) {
+		regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
+				   IMX7D_GPR12_PCIE_PHY_REFCLK_SEL,
+				   IMX7D_GPR12_PCIE_PHY_REFCLK_SEL);
+	}
+}
+
+static int imx6_pcie_suspend_noirq(struct device *dev)
+{
+	struct imx6_pcie *imx6_pcie = dev_get_drvdata(dev);
+
+	if (imx6_pcie->variant != IMX7D)
+		return 0;
+
+	imx6_pcie_clk_disable(imx6_pcie);
+	imx6_pcie_ltssm_disable(dev);
+
+	return 0;
+}
+
+static int imx6_pcie_resume_noirq(struct device *dev)
+{
+	int ret;
+	struct imx6_pcie *imx6_pcie = dev_get_drvdata(dev);
+	struct pcie_port *pp = &imx6_pcie->pci->pp;
+
+	if (imx6_pcie->variant != IMX7D)
+		return 0;
+
+	imx6_pcie_assert_core_reset(imx6_pcie);
+	imx6_pcie_init_phy(imx6_pcie);
+	imx6_pcie_deassert_core_reset(imx6_pcie);
+	dw_pcie_setup_rc(pp);
+
+	ret = imx6_pcie_establish_link(imx6_pcie);
+	if (ret < 0)
+		dev_info(dev, "pcie link is down after resume.\n");
+
+	return 0;
+}
+#endif
+
+static const struct dev_pm_ops imx6_pcie_pm_ops = {
+	SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(imx6_pcie_suspend_noirq,
+				      imx6_pcie_resume_noirq)
+};
+
 static int imx6_pcie_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct dw_pcie *pci;
 	struct imx6_pcie *imx6_pcie;
@@ -846,10 +932,11 @@ static const struct of_device_id imx6_pcie_of_match[] = {
 static struct platform_driver imx6_pcie_driver = {
 	.driver = {
 		.name	= "imx6q-pcie",
 		.of_match_table = imx6_pcie_of_match,
 		.suppress_bind_attrs = true,
+		.pm = &imx6_pcie_pm_ops,
 	},
 	.probe    = imx6_pcie_probe,
 	.shutdown = imx6_pcie_shutdown,
 };
 
-- 
2.17.1