PCI: j721e: Add suspend and resume support

Add suspend and resume support. Only the Root Complex mode is supported.

During the suspend stage PERST# is asserted, then deasserted during the
resume stage.

Link: https://lore.kernel.org/linux-pci/20240102-j7200-pcie-s2r-v7-7-a2f9156da6c3@bootlin.comSigned-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
Signed-off-by: Thomas Richard <thomas.richard@bootlin.com>
[kwilczynski: commit log, update references to the PCI SIG specification]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Siddharth Vadapalli <s-vadapalli@ti.com>

drivers/pci/controller/cadence/pci-j721e.c

@@ -7,6 +7,8 @@
  */
 
 #include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/container_of.h>
 #include <linux/delay.h>
 #include <linux/gpio/consumer.h>
 #include <linux/io.h>
@@ -22,6 +24,8 @@
 #include "../../pci.h"
 #include "pcie-cadence.h"
 
+#define cdns_pcie_to_rc(p) container_of(p, struct cdns_pcie_rc, pcie)
+
 #define ENABLE_REG_SYS_2	0x108
 #define STATUS_REG_SYS_2	0x508
 #define STATUS_CLR_REG_SYS_2	0x708
@@ -568,12 +572,12 @@ static int j721e_pcie_probe(struct platform_device *pdev)
 		pcie->refclk = clk;
 
 		/*
-		 * "Power Sequencing and Reset Signal Timings" table in
-		 * PCI EXPRESS CARD ELECTROMECHANICAL SPECIFICATION, REV. 3.0
-		 * indicates PERST# should be deasserted after minimum of 100us
-		 * once REFCLK is stable. The REFCLK to the connector in RC
-		 * mode is selected while enabling the PHY. So deassert PERST#
-		 * after 100 us.
+		 * The "Power Sequencing and Reset Signal Timings" table of the
+		 * PCI Express Card Electromechanical Specification, Revision
+		 * 5.1, Section 2.9.2, Symbol "T_PERST-CLK", indicates PERST#
+		 * should be deasserted after minimum of 100us once REFCLK is
+		 * stable. The REFCLK to the connector in RC mode is selected
+		 * while enabling the PHY. So deassert PERST# after 100 us.
 		 */
 		if (gpiod) {
 			fsleep(PCIE_T_PERST_CLK_US);
@@ -625,6 +629,87 @@ static void j721e_pcie_remove(struct platform_device *pdev)
 	pm_runtime_disable(dev);
 }
 
+static int j721e_pcie_suspend_noirq(struct device *dev)
+{
+	struct j721e_pcie *pcie = dev_get_drvdata(dev);
+
+	if (pcie->mode == PCI_MODE_RC) {
+		gpiod_set_value_cansleep(pcie->reset_gpio, 0);
+		clk_disable_unprepare(pcie->refclk);
+	}
+
+	cdns_pcie_disable_phy(pcie->cdns_pcie);
+
+	return 0;
+}
+
+static int j721e_pcie_resume_noirq(struct device *dev)
+{
+	struct j721e_pcie *pcie = dev_get_drvdata(dev);
+	struct cdns_pcie *cdns_pcie = pcie->cdns_pcie;
+	int ret;
+
+	ret = j721e_pcie_ctrl_init(pcie);
+	if (ret < 0)
+		return ret;
+
+	j721e_pcie_config_link_irq(pcie);
+
+	/*
+	 * This is not called explicitly in the probe, it is called by
+	 * cdns_pcie_init_phy().
+	 */
+	ret = cdns_pcie_enable_phy(pcie->cdns_pcie);
+	if (ret < 0)
+		return ret;
+
+	if (pcie->mode == PCI_MODE_RC) {
+		struct cdns_pcie_rc *rc = cdns_pcie_to_rc(cdns_pcie);
+
+		ret = clk_prepare_enable(pcie->refclk);
+		if (ret < 0)
+			return ret;
+
+		/*
+		 * The "Power Sequencing and Reset Signal Timings" table of the
+		 * PCI Express Card Electromechanical Specification, Revision
+		 * 5.1, Section 2.9.2, Symbol "T_PERST-CLK", indicates PERST#
+		 * should be deasserted after minimum of 100us once REFCLK is
+		 * stable. The REFCLK to the connector in RC mode is selected
+		 * while enabling the PHY. So deassert PERST# after 100 us.
+		 */
+		if (pcie->reset_gpio) {
+			fsleep(PCIE_T_PERST_CLK_US);
+			gpiod_set_value_cansleep(pcie->reset_gpio, 1);
+		}
+
+		ret = cdns_pcie_host_link_setup(rc);
+		if (ret < 0) {
+			clk_disable_unprepare(pcie->refclk);
+			return ret;
+		}
+
+		/*
+		 * Reset internal status of BARs to force reinitialization in
+		 * cdns_pcie_host_init().
+		 */
+		for (enum cdns_pcie_rp_bar bar = RP_BAR0; bar <= RP_NO_BAR; bar++)
+			rc->avail_ib_bar[bar] = true;
+
+		ret = cdns_pcie_host_init(rc);
+		if (ret) {
+			clk_disable_unprepare(pcie->refclk);
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
+static DEFINE_NOIRQ_DEV_PM_OPS(j721e_pcie_pm_ops,
+			       j721e_pcie_suspend_noirq,
+			       j721e_pcie_resume_noirq);
+
 static struct platform_driver j721e_pcie_driver = {
 	.probe  = j721e_pcie_probe,
 	.remove_new = j721e_pcie_remove,
@@ -632,6 +717,7 @@ static struct platform_driver j721e_pcie_driver = {
 		.name	= "j721e-pcie",
 		.of_match_table = of_j721e_pcie_match,
 		.suppress_bind_attrs = true,
+		.pm	= pm_sleep_ptr(&j721e_pcie_pm_ops),
 	},
 };
 builtin_platform_driver(j721e_pcie_driver);