[PATCH 1/1] PCI: layerscape: Add power management support

[PATCH 1/1] PCI: layerscape: Add power management support

[Frank Li]

From: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>

Add PME_Turn_Off/PME_TO_Ack handshake sequence, and finally
put the PCIe controller into D3 state after the L2/L3 ready
state transition process completion.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
---

This patch continue an old serial https://lore.kernel.org/lkml/20210407030948.3845-1-Zhiqiang.Hou@nxp.com/

dt-bind document about big-endian patch already accepted.

This patch fixed Krzysztof Wilczyński's comments at v5 version and reposted.


 drivers/pci/controller/dwc/pci-layerscape.c  | 408 ++++++++++++++++++-
 drivers/pci/controller/dwc/pcie-designware.h |   1 +
 2 files changed, 400 insertions(+), 9 deletions(-)

diff --git a/drivers/pci/controller/dwc/pci-layerscape.c b/drivers/pci/controller/dwc/pci-layerscape.c
index ed5fb492fe08..4e7be6b25832 100644
--- a/drivers/pci/controller/dwc/pci-layerscape.c
+++ b/drivers/pci/controller/dwc/pci-layerscape.c
@@ -8,9 +8,11 @@
  * Author: Minghuan Lian <Minghuan.Lian@freescale.com>
  */
 
+#include <linux/delay.h>
 #include <linux/kernel.h>
 #include <linux/interrupt.h>
 #include <linux/init.h>
+#include <linux/iopoll.h>
 #include <linux/of_pci.h>
 #include <linux/of_platform.h>
 #include <linux/of_address.h>
@@ -27,12 +29,59 @@
 #define PCIE_ABSERR		0x8d0 /* Bridge Slave Error Response Register */
 #define PCIE_ABSERR_SETTING	0x9401 /* Forward error of non-posted request */
 
+/* PF Message Command Register */
+#define LS_PCIE_PF_MCR		0x2c
+#define PF_MCR_PTOMR		BIT(0)
+#define PF_MCR_EXL2S		BIT(1)
+
+/* LS1021A PEXn PM Write Control Register */
+#define SCFG_PEXPMWRCR(idx)	(0x5c + (idx) * 0x64)
+#define PMXMTTURNOFF		BIT(31)
+#define SCFG_PEXSFTRSTCR	0x190
+#define PEXSR(idx)		BIT(idx)
+
+/* LS1043A PEX PME Control Register */
+#define SCFG_PEXPMECR		0x144
+#define PEXPME(idx)		BIT(31 - (idx) * 4)
+
+/* LS1043A PEX LUT Debug Register */
+#define LS_PCIE_LDBG	0x7fc
+#define LDBG_SR		BIT(30)
+#define LDBG_WE		BIT(31)
+
 #define PCIE_IATU_NUM		6
 
+#define LS_PCIE_IS_L2(v)	\
+	(((v) & PORT_LOGIC_LTSSM_STATE_MASK) == PORT_LOGIC_LTSSM_STATE_L2)
+
+struct ls_pcie;
+
+struct ls_pcie_host_pm_ops {
+	int (*pm_init)(struct ls_pcie *pcie);
+	void (*send_turn_off_message)(struct ls_pcie *pcie);
+	void (*exit_from_l2)(struct ls_pcie *pcie);
+};
+
+struct ls_pcie_drvdata {
+	const u32 pf_off;
+	const u32 lut_off;
+	const struct ls_pcie_host_pm_ops *pm_ops;
+};
+
 struct ls_pcie {
 	struct dw_pcie *pci;
+	const struct ls_pcie_drvdata *drvdata;
+	void __iomem *pf_base;
+	void __iomem *lut_base;
+	bool big_endian;
+	bool ep_presence;
+	bool pm_support;
+	struct regmap *scfg;
+	int index;
 };
 
+#define ls_pcie_lut_readl_addr(addr)	ls_pcie_lut_readl(pcie, addr)
+#define ls_pcie_pf_readl_addr(addr)	ls_pcie_pf_readl(pcie, addr)
 #define to_ls_pcie(x)	dev_get_drvdata((x)->dev)
 
 static bool ls_pcie_is_bridge(struct ls_pcie *pcie)
@@ -73,6 +122,219 @@ static void ls_pcie_fix_error_response(struct ls_pcie *pcie)
 	iowrite32(PCIE_ABSERR_SETTING, pci->dbi_base + PCIE_ABSERR);
 }
 
+static u32 ls_pcie_lut_readl(struct ls_pcie *pcie, u32 off)
+{
+	if (pcie->big_endian)
+		return ioread32be(pcie->lut_base + off);
+
+	return ioread32(pcie->lut_base + off);
+}
+
+static void ls_pcie_lut_writel(struct ls_pcie *pcie, u32 off, u32 val)
+{
+	if (pcie->big_endian)
+		return iowrite32be(val, pcie->lut_base + off);
+
+	return iowrite32(val, pcie->lut_base + off);
+}
+
+static u32 ls_pcie_pf_readl(struct ls_pcie *pcie, u32 off)
+{
+	if (pcie->big_endian)
+		return ioread32be(pcie->pf_base + off);
+
+	return ioread32(pcie->pf_base + off);
+}
+
+static void ls_pcie_pf_writel(struct ls_pcie *pcie, u32 off, u32 val)
+{
+	if (pcie->big_endian)
+		return iowrite32be(val, pcie->pf_base + off);
+
+	return iowrite32(val, pcie->pf_base + off);
+}
+
+static void ls_pcie_send_turnoff_msg(struct ls_pcie *pcie)
+{
+	u32 val;
+	int ret;
+
+	val = ls_pcie_pf_readl(pcie, LS_PCIE_PF_MCR);
+	val |= PF_MCR_PTOMR;
+	ls_pcie_pf_writel(pcie, LS_PCIE_PF_MCR, val);
+
+	ret = readx_poll_timeout(ls_pcie_pf_readl_addr, LS_PCIE_PF_MCR,
+				 val, !(val & PF_MCR_PTOMR), 100, 10000);
+	if (ret)
+		dev_warn(pcie->pci->dev, "poll turn off message timeout\n");
+}
+
+static void ls1021a_pcie_send_turnoff_msg(struct ls_pcie *pcie)
+{
+	u32 val;
+
+	if (!pcie->scfg) {
+		dev_dbg(pcie->pci->dev, "SYSCFG is NULL\n");
+		return;
+	}
+
+	/* Send Turn_off message */
+	regmap_read(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), &val);
+	val |= PMXMTTURNOFF;
+	regmap_write(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), val);
+
+	/*
+	 * 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.
+	 */
+	mdelay(10);
+
+	/* Clear Turn_off message */
+	regmap_read(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), &val);
+	val &= ~PMXMTTURNOFF;
+	regmap_write(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), val);
+}
+
+static void ls1043a_pcie_send_turnoff_msg(struct ls_pcie *pcie)
+{
+	u32 val;
+
+	if (!pcie->scfg) {
+		dev_dbg(pcie->pci->dev, "SYSCFG is NULL\n");
+		return;
+	}
+
+	/* Send Turn_off message */
+	regmap_read(pcie->scfg, SCFG_PEXPMECR, &val);
+	val |= PEXPME(pcie->index);
+	regmap_write(pcie->scfg, SCFG_PEXPMECR, val);
+
+	/*
+	 * 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.
+	 */
+	mdelay(10);
+
+	/* Clear Turn_off message */
+	regmap_read(pcie->scfg, SCFG_PEXPMECR, &val);
+	val &= ~PEXPME(pcie->index);
+	regmap_write(pcie->scfg, SCFG_PEXPMECR, val);
+}
+
+static void ls_pcie_exit_from_l2(struct ls_pcie *pcie)
+{
+	u32 val;
+	int ret;
+
+	val = ls_pcie_pf_readl(pcie, LS_PCIE_PF_MCR);
+	val |= PF_MCR_EXL2S;
+	ls_pcie_pf_writel(pcie, LS_PCIE_PF_MCR, val);
+
+	ret = readx_poll_timeout(ls_pcie_pf_readl_addr, LS_PCIE_PF_MCR,
+				 val, !(val & PF_MCR_EXL2S), 100, 10000);
+	if (ret)
+		dev_warn(pcie->pci->dev, "poll exit L2 state timeout\n");
+}
+
+static void ls_pcie_retrain_link(struct ls_pcie *pcie)
+{
+	struct dw_pcie *pci = pcie->pci;
+	u8 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
+	u32 val;
+
+	val = dw_pcie_readw_dbi(pci, offset + PCI_EXP_LNKCTL);
+	val |= PCI_EXP_LNKCTL_RL;
+	dw_pcie_writew_dbi(pci, offset + PCI_EXP_LNKCTL, val);
+}
+
+static void ls1021a_pcie_exit_from_l2(struct ls_pcie *pcie)
+{
+	u32 val;
+
+	regmap_read(pcie->scfg, SCFG_PEXSFTRSTCR, &val);
+	val |= PEXSR(pcie->index);
+	regmap_write(pcie->scfg, SCFG_PEXSFTRSTCR, val);
+
+	regmap_read(pcie->scfg, SCFG_PEXSFTRSTCR, &val);
+	val &= ~PEXSR(pcie->index);
+	regmap_write(pcie->scfg, SCFG_PEXSFTRSTCR, val);
+
+	ls_pcie_retrain_link(pcie);
+}
+
+static void ls1043a_pcie_exit_from_l2(struct ls_pcie *pcie)
+{
+	u32 val;
+
+	val = ls_pcie_lut_readl(pcie, LS_PCIE_LDBG);
+	val |= LDBG_WE;
+	ls_pcie_lut_writel(pcie, LS_PCIE_LDBG, val);
+
+	val = ls_pcie_lut_readl(pcie, LS_PCIE_LDBG);
+	val |= LDBG_SR;
+	ls_pcie_lut_writel(pcie, LS_PCIE_LDBG, val);
+
+	val = ls_pcie_lut_readl(pcie, LS_PCIE_LDBG);
+	val &= ~LDBG_SR;
+	ls_pcie_lut_writel(pcie, LS_PCIE_LDBG, val);
+
+	val = ls_pcie_lut_readl(pcie, LS_PCIE_LDBG);
+	val &= ~LDBG_WE;
+	ls_pcie_lut_writel(pcie, LS_PCIE_LDBG, val);
+
+	ls_pcie_retrain_link(pcie);
+}
+
+static int ls1021a_pcie_pm_init(struct ls_pcie *pcie)
+{
+	struct device *dev = pcie->pci->dev;
+	u32 index[2];
+	int ret;
+
+	pcie->scfg = syscon_regmap_lookup_by_phandle(dev->of_node,
+						     "fsl,pcie-scfg");
+	if (IS_ERR(pcie->scfg)) {
+		ret = PTR_ERR(pcie->scfg);
+		dev_err(dev, "No syscfg phandle specified\n");
+		goto error;
+	}
+
+	ret = of_property_read_u32_array(dev->of_node, "fsl,pcie-scfg",
+					 index, 2);
+	if (ret)
+		goto error;
+
+	pcie->index = index[1];
+
+	return 0;
+error:
+	pcie->scfg = NULL;
+	return ret;
+}
+
+static int ls_pcie_pm_init(struct ls_pcie *pcie)
+{
+	return 0;
+}
+
+static void ls_pcie_set_dstate(struct ls_pcie *pcie, u32 dstate)
+{
+	struct dw_pcie *pci = pcie->pci;
+	u8 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_PM);
+	u32 val;
+
+	val = dw_pcie_readw_dbi(pci, offset + PCI_PM_CTRL);
+	val &= ~PCI_PM_CTRL_STATE_MASK;
+	val |= dstate;
+	dw_pcie_writew_dbi(pci, offset + PCI_PM_CTRL, val);
+}
+
 static int ls_pcie_host_init(struct dw_pcie_rp *pp)
 {
 	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
@@ -86,23 +348,65 @@ static int ls_pcie_host_init(struct dw_pcie_rp *pp)
 
 	ls_pcie_drop_msg_tlp(pcie);
 
+	if (dw_pcie_link_up(pci)) {
+		dev_dbg(pci->dev, "Endpoint is present\n");
+		pcie->ep_presence = true;
+	}
+
+	if (pcie->drvdata->pm_ops && pcie->drvdata->pm_ops->pm_init &&
+	    !pcie->drvdata->pm_ops->pm_init(pcie))
+		pcie->pm_support = true;
+
 	return 0;
 }
 
+static struct ls_pcie_host_pm_ops ls1021a_pcie_host_pm_ops = {
+	.pm_init = &ls1021a_pcie_pm_init,
+	.send_turn_off_message = &ls1021a_pcie_send_turnoff_msg,
+	.exit_from_l2 = &ls1021a_pcie_exit_from_l2,
+};
+
+static struct ls_pcie_host_pm_ops ls1043a_pcie_host_pm_ops = {
+	.pm_init = &ls1021a_pcie_pm_init,
+	.send_turn_off_message = &ls1043a_pcie_send_turnoff_msg,
+	.exit_from_l2 = &ls1043a_pcie_exit_from_l2,
+};
+
+static struct ls_pcie_host_pm_ops ls_pcie_host_pm_ops = {
+	.pm_init = &ls_pcie_pm_init,
+	.send_turn_off_message = &ls_pcie_send_turnoff_msg,
+	.exit_from_l2 = &ls_pcie_exit_from_l2,
+};
+
 static const struct dw_pcie_host_ops ls_pcie_host_ops = {
 	.host_init = ls_pcie_host_init,
 };
 
+static const struct ls_pcie_drvdata ls1021a_drvdata = {
+	.pm_ops = &ls1021a_pcie_host_pm_ops,
+};
+
+static const struct ls_pcie_drvdata ls1043a_drvdata = {
+	.lut_off = 0x10000,
+	.pm_ops = &ls1043a_pcie_host_pm_ops,
+};
+
+static const struct ls_pcie_drvdata layerscape_drvdata = {
+	.lut_off = 0x80000,
+	.pf_off = 0xc0000,
+	.pm_ops = &ls_pcie_host_pm_ops,
+};
+
 static const struct of_device_id ls_pcie_of_match[] = {
-	{ .compatible = "fsl,ls1012a-pcie", },
-	{ .compatible = "fsl,ls1021a-pcie", },
-	{ .compatible = "fsl,ls1028a-pcie", },
-	{ .compatible = "fsl,ls1043a-pcie", },
-	{ .compatible = "fsl,ls1046a-pcie", },
-	{ .compatible = "fsl,ls2080a-pcie", },
-	{ .compatible = "fsl,ls2085a-pcie", },
-	{ .compatible = "fsl,ls2088a-pcie", },
-	{ .compatible = "fsl,ls1088a-pcie", },
+	{ .compatible = "fsl,ls1012a-pcie", .data = &layerscape_drvdata },
+	{ .compatible = "fsl,ls1021a-pcie", .data = &ls1021a_drvdata },
+	{ .compatible = "fsl,ls1028a-pcie", .data = &layerscape_drvdata },
+	{ .compatible = "fsl,ls1043a-pcie", .data = &ls1043a_drvdata },
+	{ .compatible = "fsl,ls1046a-pcie", .data = &layerscape_drvdata },
+	{ .compatible = "fsl,ls2080a-pcie", .data = &layerscape_drvdata },
+	{ .compatible = "fsl,ls2085a-pcie", .data = &layerscape_drvdata },
+	{ .compatible = "fsl,ls2088a-pcie", .data = &layerscape_drvdata },
+	{ .compatible = "fsl,ls1088a-pcie", .data = &layerscape_drvdata },
 	{ },
 };
 
@@ -121,6 +425,8 @@ static int ls_pcie_probe(struct platform_device *pdev)
 	if (!pci)
 		return -ENOMEM;
 
+	pcie->drvdata = of_device_get_match_data(dev);
+
 	pci->dev = dev;
 	pci->pp.ops = &ls_pcie_host_ops;
 
@@ -131,6 +437,14 @@ static int ls_pcie_probe(struct platform_device *pdev)
 	if (IS_ERR(pci->dbi_base))
 		return PTR_ERR(pci->dbi_base);
 
+	pcie->big_endian = of_property_read_bool(dev->of_node, "big-endian");
+
+	if (pcie->drvdata->lut_off)
+		pcie->lut_base = pci->dbi_base + pcie->drvdata->lut_off;
+
+	if (pcie->drvdata->pf_off)
+		pcie->pf_base = pci->dbi_base + pcie->drvdata->pf_off;
+
 	if (!ls_pcie_is_bridge(pcie))
 		return -ENODEV;
 
@@ -139,12 +453,88 @@ static int ls_pcie_probe(struct platform_device *pdev)
 	return dw_pcie_host_init(&pci->pp);
 }
 
+static bool ls_pcie_pm_check(struct ls_pcie *pcie)
+{
+	if (!pcie->ep_presence) {
+		dev_dbg(pcie->pci->dev, "Endpoint isn't present\n");
+		return false;
+	}
+
+	if (!pcie->pm_support)
+		return false;
+
+	return true;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int ls_pcie_suspend_noirq(struct device *dev)
+{
+	struct ls_pcie *pcie = dev_get_drvdata(dev);
+	struct dw_pcie *pci = pcie->pci;
+	u32 val;
+	int ret;
+
+	if (!ls_pcie_pm_check(pcie))
+		return 0;
+
+	pcie->drvdata->pm_ops->send_turn_off_message(pcie);
+
+	/* 10ms timeout to check L2 ready */
+	ret = readl_poll_timeout(pci->dbi_base + PCIE_PORT_DEBUG0,
+				 val, LS_PCIE_IS_L2(val), 100, 10000);
+	if (ret) {
+		dev_err(dev, "PCIe link enter L2 timeout! ltssm = 0x%x\n", val);
+		return ret;
+	}
+
+	ls_pcie_set_dstate(pcie, 0x3);
+
+	return 0;
+}
+
+static int ls_pcie_resume_noirq(struct device *dev)
+{
+	struct ls_pcie *pcie = dev_get_drvdata(dev);
+	struct dw_pcie *pci = pcie->pci;
+	int ret;
+
+	if (!ls_pcie_pm_check(pcie))
+		return 0;
+
+	ls_pcie_set_dstate(pcie, 0x0);
+
+	pcie->drvdata->pm_ops->exit_from_l2(pcie);
+
+	ret = ls_pcie_host_init(&pci->pp);
+	if (ret) {
+		dev_err(dev, "PCIe host init failed! ret = 0x%x\n", ret);
+		return ret;
+	}
+
+	dw_pcie_setup_rc(&pci->pp);
+
+	ret = dw_pcie_wait_for_link(pci);
+	if (ret) {
+		dev_err(dev, "Wait link up timeout! ret = 0x%x\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+#endif /* CONFIG_PM_SLEEP */
+
+static const struct dev_pm_ops ls_pcie_pm_ops = {
+	SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(ls_pcie_suspend_noirq,
+				      ls_pcie_resume_noirq)
+};
+
 static struct platform_driver ls_pcie_driver = {
 	.probe = ls_pcie_probe,
 	.driver = {
 		.name = "layerscape-pcie",
 		.of_match_table = ls_pcie_of_match,
 		.suppress_bind_attrs = true,
+		.pm = &ls_pcie_pm_ops,
 	},
 };
 builtin_platform_driver(ls_pcie_driver);
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 79713ce075cc..7de8409e2433 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -94,6 +94,7 @@
 #define PCIE_PORT_DEBUG0		0x728
 #define PORT_LOGIC_LTSSM_STATE_MASK	0x1f
 #define PORT_LOGIC_LTSSM_STATE_L0	0x11
+#define PORT_LOGIC_LTSSM_STATE_L2	0x15
 #define PCIE_PORT_DEBUG1		0x72C
 #define PCIE_PORT_DEBUG1_LINK_UP		BIT(4)
 #define PCIE_PORT_DEBUG1_LINK_IN_TRAINING	BIT(29)
-- 
2.34.1

Re: [PATCH 1/1] PCI: layerscape: Add power management support

[Bjorn Helgaas]

On Fri, Mar 17, 2023 at 04:05:28PM -0400, Frank Li wrote:
> From: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
> 
> Add PME_Turn_Off/PME_TO_Ack handshake sequence, and finally
> put the PCIe controller into D3 state after the L2/L3 ready
> state transition process completion.

Can you please include a sentence or two about what this means for
devices below the PCIe controller?  Is this guaranteed to be safe for
them, i.e., can all PCIe devices tolerate PME_Turn_Off, etc., and
resume correctly afterwards?

I suspect other drivers will copy this sort of pattern if it is safe
and useful.

>  struct ls_pcie {
>  	struct dw_pcie *pci;
> +	const struct ls_pcie_drvdata *drvdata;
> +	void __iomem *pf_base;
> +	void __iomem *lut_base;
> +	bool big_endian;
> +	bool ep_presence;

This means "any downstream device present", right?  Could be an
Endpoint or could be a Switch Upstream Port?  I guess it's basically a
cache of dw_pcie_link_up() at ls_pcie_host_init()-time.

> +	bool pm_support;
> +	struct regmap *scfg;
> +	int index;
>  };

> +static void ls1021a_pcie_send_turnoff_msg(struct ls_pcie *pcie)
> +{
> +	u32 val;
> +
> +	if (!pcie->scfg) {
> +		dev_dbg(pcie->pci->dev, "SYSCFG is NULL\n");
> +		return;
> +	}
> +
> +	/* Send Turn_off message */
> +	regmap_read(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), &val);
> +	val |= PMXMTTURNOFF;
> +	regmap_write(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), val);
> +
> +	/*
> +	 * 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.

Spec citation please.

> +	 */
> +	mdelay(10);
> +
> +	/* Clear Turn_off message */
> +	regmap_read(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), &val);
> +	val &= ~PMXMTTURNOFF;
> +	regmap_write(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), val);
> +}

> +static bool ls_pcie_pm_check(struct ls_pcie *pcie)

This is used as a boolean ("if (!ls_pcie_pm_check())") so it needs a
better name.  "Check" doesn't give any hint about what a true or false
return value means.  Something like "pm_supported" *would* give a
hint because "if (!ls_pcie_pm_supported())" is a sensible question to
ask.

> +{
> +	if (!pcie->ep_presence) {
> +		dev_dbg(pcie->pci->dev, "Endpoint isn't present\n");
> +		return false;
> +	}
> +
> +	if (!pcie->pm_support)
> +		return false;

Why test the negative ("!pcie->pm_support") and then return false?
How about:

  if (pcie->pm_support)
    return true;

  return false;

or even better, just:

  return pcie->pm_support;

> +	return true;
> +}

RE: [EXT] Re: [PATCH 1/1] PCI: layerscape: Add power management support

[Frank Li]

> 
> Caution: EXT Email
> 
> On Fri, Mar 17, 2023 at 04:05:28PM -0400, Frank Li wrote:
> > From: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
> >
> > Add PME_Turn_Off/PME_TO_Ack handshake sequence, and finally
> > put the PCIe controller into D3 state after the L2/L3 ready
> > state transition process completion.
> 
> Can you please include a sentence or two about what this means for
> devices below the PCIe controller?  Is this guaranteed to be safe for
> them, i.e., can all PCIe devices tolerate PME_Turn_Off, etc., and
> resume correctly afterwards?

We can't guarantee all PCIe devices tolerate PME_Turn_off etc. We just
follow PCI Spec and test some available devices to make sure our implement
 is correct.

Anyways, it was still better than nothing.  

> 
> I suspect other drivers will copy this sort of pattern if it is safe
> and useful.
> 
> >  struct ls_pcie {
> >       struct dw_pcie *pci;
> > +     const struct ls_pcie_drvdata *drvdata;
> > +     void __iomem *pf_base;
> > +     void __iomem *lut_base;
> > +     bool big_endian;
> > +     bool ep_presence;
> 
> This means "any downstream device present", right?  Could be an
> Endpoint or could be a Switch Upstream Port?  I guess it's basically a
> cache of dw_pcie_link_up() at ls_pcie_host_init()-time.

Should be an Endpoint.  Most of our user case is that connect pcie
wifi module.   

> 
> > +     bool pm_support;
> > +     struct regmap *scfg;
> > +     int index;
> >  };
> 
> > +static void ls1021a_pcie_send_turnoff_msg(struct ls_pcie *pcie)
> > +{
> > +     u32 val;
> > +
> > +     if (!pcie->scfg) {
> > +             dev_dbg(pcie->pci->dev, "SYSCFG is NULL\n");
> > +             return;
> > +     }
> > +
> > +     /* Send Turn_off message */
> > +     regmap_read(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), &val);
> > +     val |= PMXMTTURNOFF;
> > +     regmap_write(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), val);
> > +
> > +     /*
> > +      * 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.
> 
> Spec citation please.
> 
> > +      */
> > +     mdelay(10);
> > +
> > +     /* Clear Turn_off message */
> > +     regmap_read(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), &val);
> > +     val &= ~PMXMTTURNOFF;
> > +     regmap_write(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), val);
> > +}
> 
> > +static bool ls_pcie_pm_check(struct ls_pcie *pcie)
> 
> This is used as a boolean ("if (!ls_pcie_pm_check())") so it needs a
> better name.  "Check" doesn't give any hint about what a true or false
> return value means.  Something like "pm_supported" *would* give a
> hint because "if (!ls_pcie_pm_supported())" is a sensible question to
> ask.
> 
> > +{
> > +     if (!pcie->ep_presence) {
> > +             dev_dbg(pcie->pci->dev, "Endpoint isn't present\n");
> > +             return false;
> > +     }
> > +
> > +     if (!pcie->pm_support)
> > +             return false;
> 
> Why test the negative ("!pcie->pm_support") and then return false?
> How about:
> 
>   if (pcie->pm_support)
>     return true;
> 
>   return false;
> 
> or even better, just:
> 
>   return pcie->pm_support;
> 
> > +     return true;
> > +}