linux-kernel - [PATCH v2 4/4] PCI: imx: Add PME_Turn

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Message-ID: <37d60fe2119361381a6a81f439fa1c3ad29db45e.1538670431.git.leonard.crestez@nxp.com>
Date:   Thu, 4 Oct 2018 16:34:30 +0000
From:   Leonard Crestez <leonard.crestez@....com>
To:     Lucas Stach <l.stach@...gutronix.de>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Richard Zhu <hongxing.zhu@....com>
CC:     Andrey Smirnov <andrew.smirnov@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Jingoo Han <jingoohan1@...il.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Fabio Estevam <fabio.estevam@....com>,
        dl-linux-imx <linux-imx@....com>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH v2 4/4] PCI: imx: Add PME_Turn_Off support

When the root complex suspends it must send a PME_Turn_Off TLP.
Implement this by asserting the "turnoff" reset.

On imx7d this functionality is part of the SRC and exposed through the
linux reset-controller subsystem. On imx6 equivalent bits are in the
IOMUXC GPR area which the imx6-pcie driver accesses directly.

This is only for imx7d right now but it's deliberately implemented as an
optional reset, ignoring the chip variant:
* Older dtbs won't have this reset so it will be ignored.
* Future chips might also expose this as a reset controller.

For example imx8m (not yet supported) has the exact same
PCIE_CTRL_APPS_TURNOFF bit in the same location.

Signed-off-by: Leonard Crestez <leonard.crestez@....com>
---
 drivers/pci/controller/dwc/pci-imx6.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index 6ba16fd1373c..2bf80f1ad852 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -50,10 +50,11 @@ struct imx6_pcie {
 	struct clk		*pcie_inbound_axi;
 	struct clk		*pcie;
 	struct regmap		*iomuxc_gpr;
 	struct reset_control	*pciephy_reset;
 	struct reset_control	*apps_reset;
+	struct reset_control	*turnoff_reset;
 	enum imx6_pcie_variants variant;
 	u32			tx_deemph_gen1;
 	u32			tx_deemph_gen2_3p5db;
 	u32			tx_deemph_gen2_6db;
 	u32			tx_swing_full;
@@ -812,10 +813,25 @@ static void imx6_pcie_ltssm_disable(struct device *dev)
 	default:
 		dev_err(dev, "ltssm_disable not supported\n");
 	}
 }
 
+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);
+
+	/*
+	 * Components with an upstream port must respond to
+	 * PME_Turn_Off with PME_TO_Ack but we can't check.
+	 *
+	 * The standard recommends a 1-10ms timeout after which to
+	 * proceed anyway as if acks were received.
+	 */
+	usleep_range(1000, 10000);
+}
+
 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);
@@ -832,10 +848,11 @@ 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_pm_turnoff(imx6_pcie);
 	imx6_pcie_clk_disable(imx6_pcie);
 	imx6_pcie_ltssm_disable(dev);
 
 	return 0;
 }
@@ -959,10 +976,17 @@ static int imx6_pcie_probe(struct platform_device *pdev)
 		break;
 	default:
 		break;
 	}
 
+	/* Grab turnoff reset */
+	imx6_pcie->turnoff_reset = devm_reset_control_get_optional_exclusive(dev, "turnoff");
+	if (IS_ERR(imx6_pcie->turnoff_reset)) {
+		dev_err(dev, "Failed to get TURNOFF reset control\n");
+		return PTR_ERR(imx6_pcie->turnoff_reset);
+	}
+
 	/* Grab GPR config register range */
 	imx6_pcie->iomuxc_gpr =
 		 syscon_regmap_lookup_by_compatible("fsl,imx6q-iomuxc-gpr");
 	if (IS_ERR(imx6_pcie->iomuxc_gpr)) {
 		dev_err(dev, "unable to find iomuxc registers\n");
-- 
2.17.1