PCI: imx: Add imx6sx suspend/resume support

Enable PCI suspend/resume support on imx6sx SOCs. This is similar to
imx7d with a few differences:

* The PM_Turn_Off bit is exposed through an IOMUX GPR, like all other
pcie control bits on 6sx.
* The pcie_inbound_axi clk needs to be turned off in suspend. On resume
it is restored via resume -> deassert_core_reset -> enable_ref_clk.

Most of the resume logic is shared with the initial reset after probe.

Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Acked-by: Lucas Stach <l.stach@pengutronix.de>

1 files changed, 39 insertions, 5 deletions

diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index 4a307cdf20c8..25a2b7683e55 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -817,8 +817,28 @@ static void imx6_pcie_ltssm_disable(struct device *dev)
 
 static void imx6_pcie_pm_turnoff(struct imx6_pcie *imx6_pcie)
 {
-        reset_control_assert(imx6_pcie->turnoff_reset);
-        reset_control_deassert(imx6_pcie->turnoff_reset);
+        struct device *dev = imx6_pcie->pci->dev;
+
+        /* Some variants have a turnoff reset in DT */
+        if (imx6_pcie->turnoff_reset) {
+                reset_control_assert(imx6_pcie->turnoff_reset);
+                reset_control_deassert(imx6_pcie->turnoff_reset);
+                goto pm_turnoff_sleep;
+        }
+
+        /* Others poke directly at IOMUXC registers */
+        switch (imx6_pcie->variant) {
+        case IMX6SX:
+                regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
+                                IMX6SX_GPR12_PCIE_PM_TURN_OFF,
+                                IMX6SX_GPR12_PCIE_PM_TURN_OFF);
+                regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
+                                IMX6SX_GPR12_PCIE_PM_TURN_OFF, 0);
+                break;
+        default:
+                dev_err(dev, "PME_Turn_Off not implemented\n");
+                return;
+        }
 
         /*
          * Components with an upstream port must respond to
@@ -827,6 +847,7 @@ static void imx6_pcie_pm_turnoff(struct imx6_pcie *imx6_pcie)
          * The standard recommends a 1-10ms timeout after which to
          * proceed anyway as if acks were received.
          */
+pm_turnoff_sleep:
         usleep_range(1000, 10000);
 }
 
@@ -836,18 +857,31 @@ static void imx6_pcie_clk_disable(struct imx6_pcie *imx6_pcie)
         clk_disable_unprepare(imx6_pcie->pcie_phy);
         clk_disable_unprepare(imx6_pcie->pcie_bus);
 
-        if (imx6_pcie->variant == IMX7D) {
+        switch (imx6_pcie->variant) {
+        case IMX6SX:
+                clk_disable_unprepare(imx6_pcie->pcie_inbound_axi);
+                break;
+        case IMX7D:
                 regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
                                    IMX7D_GPR12_PCIE_PHY_REFCLK_SEL,
                                    IMX7D_GPR12_PCIE_PHY_REFCLK_SEL);
+                break;
+        default:
+                break;
         }
 }
 
+static inline bool imx6_pcie_supports_suspend(struct imx6_pcie *imx6_pcie)
+{
+        return (imx6_pcie->variant == IMX7D ||
+                imx6_pcie->variant == IMX6SX);
+}
+
 static int imx6_pcie_suspend_noirq(struct device *dev)
 {
         struct imx6_pcie *imx6_pcie = dev_get_drvdata(dev);
 
-        if (imx6_pcie->variant != IMX7D)
+        if (!imx6_pcie_supports_suspend(imx6_pcie))
                 return 0;
 
         imx6_pcie_pm_turnoff(imx6_pcie);
@@ -863,7 +897,7 @@ static int imx6_pcie_resume_noirq(struct device *dev)
         struct imx6_pcie *imx6_pcie = dev_get_drvdata(dev);
         struct pcie_port *pp = &imx6_pcie->pci->pp;
 
-        if (imx6_pcie->variant != IMX7D)
+        if (!imx6_pcie_supports_suspend(imx6_pcie))
                 return 0;
 
         imx6_pcie_assert_core_reset(imx6_pcie);