Date:   Tue, 20 Sep 2022 15:52:23 +0530
From:   Krishna chaitanya chundru <quic_krichai@...cinc.com>
To:     helgaas@...nel.org
Cc:     linux-pci@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, mka@...omium.org,
        quic_vbadigan@...cinc.com, quic_hemantk@...cinc.com,
        quic_nitegupt@...cinc.com, quic_skananth@...cinc.com,
        quic_ramkri@...cinc.com, manivannan.sadhasivam@...aro.org,
        swboyd@...omium.org, dmitry.baryshkov@...aro.org,
        svarbanov@...sol.com, agross@...nel.org, andersson@...nel.org,
        konrad.dybcio@...ainline.org, lpieralisi@...nel.org,
        robh@...nel.org, kw@...ux.com, bhelgaas@...gle.com,
        linux-phy@...ts.infradead.org, vkoul@...nel.org, kishon@...com,
        mturquette@...libre.com, linux-clk@...r.kernel.org,
        Krishna chaitanya chundru <quic_krichai@...cinc.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: [PATCH v7 1/5] PCI: qcom: Add system suspend and resume support

Add suspend and resume syscore ops.

Few PCIe endpoints like NVMe and WLANs are always expecting the device
to be in D0 state and the link to be active (or in l1ss) all the time
(including in S3 state).

In qcom platform PCIe resources( clocks, phy etc..) can released
when the link is in L1ss to reduce the power consumption. So if the link
is in L1ss, release the PCIe resources. And when the system resumes,
enable the PCIe resources if they released in the suspend path.

is_suspended flag indicates if the PCIe resources are released or not
in the suspend path.

Its observed that access to Ep PCIe space to mask MSI/MSIX is happening
at the very late stage of suspend path (access by affinity changes while
making CPUs offline during suspend, this will happen after devices are
suspended (after all phases of suspend ops)). If we turn off clocks in
any PM callback, afterwards running into crashes due to un-clocked access
due to above mentioned MSI/MSIx access.
So, we are making use of syscore framework to turn off the PCIe clocks
which will be called after making CPUs offline.

Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
---
changes since v6:
	- move the supports_system_suspend check to syscore ops.
changes since v5:
	- Rebasing the code and replaced pm ops with syscore ops as
	  we are getting access to pci region after pm ops. syscore ops
	  will called after disabling non boot cpus and there is no pci
	  access after that.
Changes since v4:
	- Rebasing the code and removed the supports_system_suspend flag
	- in the resume path as is_suspended will serve its purpose.
Changes since v3:
	- Powering down the phy in suspend and powering it on resume to
	  achieve maximum power savings.
Changes since v2:
	- Replaced the enable, disable clks ops with suspend and resume
	- Renamed support_pm_opsi flag  with supports_system_suspend.
Changes since v1:
	- Fixed compilation errors.
---
 drivers/pci/controller/dwc/pcie-qcom.c | 139 ++++++++++++++++++++++++++++++++-
 1 file changed, 138 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index 39ca06f..3f5424a 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -27,6 +27,7 @@
 #include <linux/reset.h>
 #include <linux/slab.h>
 #include <linux/types.h>
+#include <linux/syscore_ops.h>
 
 #include "../../pci.h"
 #include "pcie-designware.h"
@@ -44,6 +45,9 @@
 #define PCIE20_PARF_PM_CTRL			0x20
 #define REQ_NOT_ENTR_L1				BIT(5)
 
+#define PCIE20_PARF_PM_STTS			0x24
+#define PCIE20_PARF_PM_STTS_LINKST_IN_L1SUB	BIT(8)
+
 #define PCIE20_PARF_PHY_CTRL			0x40
 #define PHY_CTRL_PHY_TX0_TERM_OFFSET_MASK	GENMASK(20, 16)
 #define PHY_CTRL_PHY_TX0_TERM_OFFSET(x)		((x) << 16)
@@ -122,6 +126,8 @@
 
 #define QCOM_PCIE_CRC8_POLYNOMIAL (BIT(2) | BIT(1) | BIT(0))
 
+static LIST_HEAD(qcom_pcie_list);
+
 struct qcom_pcie_resources_2_1_0 {
 	struct clk_bulk_data clks[QCOM_PCIE_2_1_0_MAX_CLOCKS];
 	struct reset_control *pci_reset;
@@ -211,13 +217,21 @@ struct qcom_pcie_ops {
 	void (*post_deinit)(struct qcom_pcie *pcie);
 	void (*ltssm_enable)(struct qcom_pcie *pcie);
 	int (*config_sid)(struct qcom_pcie *pcie);
+	int (*suspend)(struct qcom_pcie *pcie);
+	int (*resume)(struct qcom_pcie *pcie);
 };
 
 struct qcom_pcie_cfg {
 	const struct qcom_pcie_ops *ops;
+	/*
+	 * Flag ensures which devices will turn off clks, phy
+	 * in system suspend.
+	 */
+	unsigned int supports_system_suspend:1;
 };
 
 struct qcom_pcie {
+	struct list_head list;	/* list to probed instances */
 	struct dw_pcie *pci;
 	void __iomem *parf;			/* DT parf */
 	void __iomem *elbi;			/* DT elbi */
@@ -225,10 +239,14 @@ struct qcom_pcie {
 	struct phy *phy;
 	struct gpio_desc *reset;
 	const struct qcom_pcie_cfg *cfg;
+	unsigned int is_suspended:1;
 };
 
 #define to_qcom_pcie(x)		dev_get_drvdata((x)->dev)
 
+static int __maybe_unused qcom_pcie_syscore_op_suspend(void);
+static void __maybe_unused qcom_pcie_syscore_op_resume(void);
+
 static void qcom_ep_reset_assert(struct qcom_pcie *pcie)
 {
 	gpiod_set_value_cansleep(pcie->reset, 1);
@@ -1301,6 +1319,28 @@ static void qcom_pcie_deinit_2_7_0(struct qcom_pcie *pcie)
 	regulator_bulk_disable(ARRAY_SIZE(res->supplies), res->supplies);
 }
 
+static int qcom_pcie_resume_2_7_0(struct qcom_pcie *pcie)
+{
+	struct qcom_pcie_resources_2_7_0 *res = &pcie->res.v2_7_0;
+	int ret;
+
+	ret = clk_bulk_prepare_enable(res->num_clks, res->clks);
+
+	phy_power_on(pcie->phy);
+
+	return ret;
+}
+
+static int qcom_pcie_suspend_2_7_0(struct qcom_pcie *pcie)
+{
+	struct qcom_pcie_resources_2_7_0 *res = &pcie->res.v2_7_0;
+
+	phy_power_off(pcie->phy);
+
+	clk_bulk_disable_unprepare(res->num_clks, res->clks);
+	return 0;
+}
+
 static int qcom_pcie_get_resources_2_9_0(struct qcom_pcie *pcie)
 {
 	struct qcom_pcie_resources_2_9_0 *res = &pcie->res.v2_9_0;
@@ -1594,6 +1634,8 @@ static const struct qcom_pcie_ops ops_1_9_0 = {
 	.deinit = qcom_pcie_deinit_2_7_0,
 	.ltssm_enable = qcom_pcie_2_3_2_ltssm_enable,
 	.config_sid = qcom_pcie_config_sid_sm8250,
+	.suspend = qcom_pcie_suspend_2_7_0,
+	.resume = qcom_pcie_resume_2_7_0,
 };
 
 /* Qcom IP rev.: 2.9.0  Synopsys IP rev.: 5.00a */
@@ -1613,6 +1655,11 @@ static const struct qcom_pcie_cfg cfg_1_9_0 = {
 	.ops = &ops_1_9_0,
 };
 
+static const struct qcom_pcie_cfg sc7280_cfg = {
+	.ops = &ops_1_9_0,
+	.supports_system_suspend = true,
+};
+
 static const struct qcom_pcie_cfg cfg_2_1_0 = {
 	.ops = &ops_2_1_0,
 };
@@ -1642,6 +1689,23 @@ static const struct dw_pcie_ops dw_pcie_ops = {
 	.start_link = qcom_pcie_start_link,
 };
 
+/*
+ * There is access to Ep PCIe space to mask MSI/MSIX after pm suspend
+ * ops.(getting hit by affinity changes while making CPUs offline during
+ * suspend, this will happen after devices are suspended
+ * (all phases of suspend ops)).
+ *
+ * When registered with pm ops there is a crash due to un-clocked access,
+ * as in the pm suspend op clocks are disabled.
+ *
+ * So, registering with syscore ops which will called after making
+ * CPU's offline.
+ */
+static struct syscore_ops qcom_pcie_syscore_ops = {
+	.suspend = qcom_pcie_syscore_op_suspend,
+	.resume = qcom_pcie_syscore_op_resume,
+};
+
 static int qcom_pcie_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -1720,6 +1784,17 @@ static int qcom_pcie_probe(struct platform_device *pdev)
 		goto err_phy_exit;
 	}
 
+	/* Register for syscore ops only when first instance probed */
+	if (list_empty(&qcom_pcie_list))
+		register_syscore_ops(&qcom_pcie_syscore_ops);
+
+	/*
+	 * Add the qcom_pcie list of each PCIe instance probed to
+	 * the global list so that we use it iterate through each PCIe
+	 * instance in the syscore ops.
+	 */
+	list_add_tail(&pcie->list, &qcom_pcie_list);
+
 	return 0;
 
 err_phy_exit:
@@ -1731,6 +1806,68 @@ static int qcom_pcie_probe(struct platform_device *pdev)
 	return ret;
 }
 
+static int __maybe_unused qcom_pcie_pm_suspend(struct qcom_pcie *pcie)
+{
+	u32 val;
+	struct dw_pcie *pci = pcie->pci;
+	struct device *dev = pci->dev;
+
+	/* if the link is not active turn off clocks */
+	if (!dw_pcie_link_up(pci)) {
+		dev_dbg(dev, "Link is not active\n");
+		goto suspend;
+	}
+
+	/* if the link is not in l1ss don't turn off clocks */
+	val = readl(pcie->parf + PCIE20_PARF_PM_STTS);
+	if (!(val & PCIE20_PARF_PM_STTS_LINKST_IN_L1SUB)) {
+		dev_warn(dev, "Link is not in L1ss\n");
+		return 0;
+	}
+
+suspend:
+	if (pcie->cfg->ops->suspend)
+		pcie->cfg->ops->suspend(pcie);
+
+	pcie->is_suspended = true;
+
+	return 0;
+}
+
+static int __maybe_unused qcom_pcie_pm_resume(struct qcom_pcie *pcie)
+{
+	if (!pcie->is_suspended)
+		return 0;
+
+	if (pcie->cfg->ops->resume)
+		pcie->cfg->ops->resume(pcie);
+
+	pcie->is_suspended = false;
+
+	return 0;
+}
+
+static int __maybe_unused qcom_pcie_syscore_op_suspend(void)
+{
+	struct qcom_pcie *qcom_pcie;
+
+	list_for_each_entry(qcom_pcie, &qcom_pcie_list, list) {
+
+		if (qcom_pcie->cfg->supports_system_suspend)
+			qcom_pcie_pm_suspend(qcom_pcie);
+	}
+	return 0;
+}
+
+static void __maybe_unused qcom_pcie_syscore_op_resume(void)
+{
+	struct qcom_pcie *qcom_pcie;
+
+	list_for_each_entry(qcom_pcie, &qcom_pcie_list, list) {
+		qcom_pcie_pm_resume(qcom_pcie);
+	}
+}
+
 static const struct of_device_id qcom_pcie_match[] = {
 	{ .compatible = "qcom,pcie-apq8064", .data = &cfg_2_1_0 },
 	{ .compatible = "qcom,pcie-apq8084", .data = &cfg_1_0_0 },
@@ -1742,7 +1879,7 @@ static const struct of_device_id qcom_pcie_match[] = {
 	{ .compatible = "qcom,pcie-msm8996", .data = &cfg_2_3_2 },
 	{ .compatible = "qcom,pcie-qcs404", .data = &cfg_2_4_0 },
 	{ .compatible = "qcom,pcie-sa8540p", .data = &cfg_1_9_0 },
-	{ .compatible = "qcom,pcie-sc7280", .data = &cfg_1_9_0 },
+	{ .compatible = "qcom,pcie-sc7280", .data = &sc7280_cfg },
 	{ .compatible = "qcom,pcie-sc8180x", .data = &cfg_1_9_0 },
 	{ .compatible = "qcom,pcie-sc8280xp", .data = &cfg_1_9_0 },
 	{ .compatible = "qcom,pcie-sdm845", .data = &cfg_2_7_0 },
-- 
2.7.4

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