[PATCH 19/19] PCI: rockchip-ep: Handle PERST signal in endpoint mode

[Damien Le Moal <dlemoal@kernel.org>]

Currently, the Rockchip PCIe endpoint controller driver does not handle
PERST signal, which prevents detecting when link training should
actually be started or if the host reset the device. This however can
be supported using the controller ep_gpio, set as an input GPIO for
endpoint mode.

Modify the endpoint rockchip driver to get the ep_gpio and its
associated interrupt which is serviced using a threaded IRQ with the
function rockchip_pcie_ep_perst_irq_thread() as handler.

This handler function notifies a link down event corresponding to the RC
side asserting the PERST signal using pci_epc_linkdown() when the gpio
is high. Once the gpio value goes down, corresponding to the RC
de-asserting the PERST signal, link training is started. The polarity
of the gpio interrupt trigger is changed from high to low after the RC
asserted PERST, and conversely changed from low to high after the RC
de-asserts PERST.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
---
 drivers/pci/controller/pcie-rockchip-ep.c | 118 +++++++++++++++++++++-
 drivers/pci/controller/pcie-rockchip.c    |  12 +--
 2 files changed, 122 insertions(+), 8 deletions(-)

diff --git a/drivers/pci/controller/pcie-rockchip-ep.c b/drivers/pci/controller/pcie-rockchip-ep.c
index d8e56b4a5578..501d25f7284c 100644
--- a/drivers/pci/controller/pcie-rockchip-ep.c
+++ b/drivers/pci/controller/pcie-rockchip-ep.c
@@ -18,6 +18,7 @@
 #include <linux/sizes.h>
 #include <linux/workqueue.h>
 #include <linux/iopoll.h>
+#include <linux/gpio/consumer.h>
 
 #include "pcie-rockchip.h"
 
@@ -50,6 +51,9 @@ struct rockchip_pcie_ep {
 	u64			irq_pci_addr;
 	u8			irq_pci_fn;
 	u8			irq_pending;
+	int			perst_irq;
+	bool			perst_asserted;
+	bool 			link_up;
 	struct delayed_work	link_training;
 };
 
@@ -464,13 +468,17 @@ static int rockchip_pcie_ep_start(struct pci_epc *epc)
 
 	rockchip_pcie_write(rockchip, cfg, PCIE_CORE_PHY_FUNC_CFG);
 
+	if (rockchip->ep_gpio)
+		enable_irq(ep->perst_irq);
+
 	/* Enable configuration and start link training */
 	rockchip_pcie_write(rockchip,
 			    PCIE_CLIENT_LINK_TRAIN_ENABLE |
 			    PCIE_CLIENT_CONF_ENABLE,
 			    PCIE_CLIENT_CONFIG);
 
-	schedule_delayed_work(&ep->link_training, 0);
+	if (!rockchip->ep_gpio)
+		schedule_delayed_work(&ep->link_training, 0);
 
 	return 0;
 }
@@ -480,6 +488,11 @@ static void rockchip_pcie_ep_stop(struct pci_epc *epc)
 	struct rockchip_pcie_ep *ep = epc_get_drvdata(epc);
 	struct rockchip_pcie *rockchip = &ep->rockchip;
 
+	if (rockchip->ep_gpio) {
+		ep->perst_asserted = true;
+		disable_irq(ep->perst_irq);
+	}
+
 	cancel_delayed_work_sync(&ep->link_training);
 
 	/* Stop link training and disable configuration */
@@ -542,6 +555,13 @@ static void rockchip_pcie_ep_link_training(struct work_struct *work)
 	if (!rockchip_pcie_ep_link_up(rockchip))
 		goto again;
 
+	/*
+	 * If PERST was asserted while polling the link, do not notify
+	 * the function.
+	 */
+	if (ep->perst_asserted)
+		return;
+
 	val = rockchip_pcie_read(rockchip, PCIE_CLIENT_BASIC_STATUS0);
 	dev_info(dev,
 		 "Link UP (Negociated speed: %sGT/s, width: x%lu)\n",
@@ -551,6 +571,7 @@ static void rockchip_pcie_ep_link_training(struct work_struct *work)
 
 	/* Notify the function */
 	pci_epc_linkup(ep->epc);
+	ep->link_up = true;
 
 	return;
 
@@ -558,6 +579,94 @@ static void rockchip_pcie_ep_link_training(struct work_struct *work)
 	schedule_delayed_work(&ep->link_training, msecs_to_jiffies(5));
 }
 
+static void rockchip_pcie_ep_perst_assert(struct rockchip_pcie_ep *ep)
+{
+	struct rockchip_pcie *rockchip = &ep->rockchip;
+	struct device *dev = rockchip->dev;
+
+	dev_dbg(dev, "PERST asserted, link down\n");
+
+	if (ep->perst_asserted)
+		return;
+
+	ep->perst_asserted = true;
+
+	cancel_delayed_work_sync(&ep->link_training);
+
+	if (ep->link_up) {
+		pci_epc_linkdown(ep->epc);
+		ep->link_up = false;
+	}
+}
+
+static void rockchip_pcie_ep_perst_deassert(struct rockchip_pcie_ep *ep)
+{
+	struct rockchip_pcie *rockchip = &ep->rockchip;
+	struct device *dev = rockchip->dev;
+
+	dev_dbg(dev, "PERST de-asserted, starting link training\n");
+
+	if (!ep->perst_asserted)
+		return;
+
+	ep->perst_asserted = false;
+
+	/* Enable link re-training */
+	rockchip_pcie_ep_retrain_link(rockchip);
+
+	/* Start link training */
+	schedule_delayed_work(&ep->link_training, 0);
+}
+
+static irqreturn_t rockchip_pcie_ep_perst_irq_thread(int irq, void *data)
+{
+	struct pci_epc *epc = data;
+	struct rockchip_pcie_ep *ep = epc_get_drvdata(epc);
+	struct rockchip_pcie *rockchip = &ep->rockchip;
+	u32 perst = gpiod_get_value(rockchip->ep_gpio);
+
+	if (perst)
+		rockchip_pcie_ep_perst_assert(ep);
+	else
+		rockchip_pcie_ep_perst_deassert(ep);
+
+	irq_set_irq_type(ep->perst_irq,
+			 (perst ? IRQF_TRIGGER_HIGH : IRQF_TRIGGER_LOW));
+
+	return IRQ_HANDLED;
+}
+
+static int rockchip_pcie_ep_setup_irq(struct pci_epc *epc)
+{
+	struct rockchip_pcie_ep *ep = epc_get_drvdata(epc);
+	struct rockchip_pcie *rockchip = &ep->rockchip;
+	struct device *dev = rockchip->dev;
+	int ret;
+
+	if (!rockchip->ep_gpio)
+		return 0;
+
+	/* PCIe reset interrupt */
+	ep->perst_irq = gpiod_to_irq(rockchip->ep_gpio);
+	if (ep->perst_irq < 0) {
+		dev_err(dev, "No corresponding IRQ for PERST GPIO\n");
+		return ep->perst_irq;
+	}
+
+	ep->perst_asserted = true;
+	irq_set_status_flags(ep->perst_irq, IRQ_NOAUTOEN);
+	ret = devm_request_threaded_irq(dev, ep->perst_irq, NULL,
+					rockchip_pcie_ep_perst_irq_thread,
+					IRQF_TRIGGER_HIGH | IRQF_ONESHOT,
+					"pcie-ep-perst", epc);
+	if (ret) {
+		dev_err(dev, "Request PERST GPIO IRQ failed %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
 static const struct pci_epc_features rockchip_pcie_epc_features = {
 	.linkup_notifier = true,
 	.msi_capable = true,
@@ -721,6 +830,7 @@ static int rockchip_pcie_ep_probe(struct platform_device *pdev)
 	rockchip->is_rc = false;
 	rockchip->dev = dev;
 	INIT_DELAYED_WORK(&ep->link_training, rockchip_pcie_ep_link_training);
+	ep->link_up = false;
 
 	epc = devm_pci_epc_create(dev, &rockchip_pcie_epc_ops);
 	if (IS_ERR(epc)) {
@@ -748,7 +858,13 @@ static int rockchip_pcie_ep_probe(struct platform_device *pdev)
 	/* Only enable function 0 by default */
 	rockchip_pcie_write(rockchip, BIT(0), PCIE_CORE_PHY_FUNC_CFG);
 
+	err = rockchip_pcie_ep_setup_irq(epc);
+	if (err < 0)
+		goto err_uninit_port;
+
 	return 0;
+err_uninit_port:
+	rockchip_pcie_deinit_phys(rockchip);
 err_release_resources:
 	rockchip_pcie_ep_release_resources(ep);
 err_disable_clocks:
diff --git a/drivers/pci/controller/pcie-rockchip.c b/drivers/pci/controller/pcie-rockchip.c
index dbec700ba9f9..3938c0b6b5a9 100644
--- a/drivers/pci/controller/pcie-rockchip.c
+++ b/drivers/pci/controller/pcie-rockchip.c
@@ -119,13 +119,11 @@ int rockchip_pcie_parse_dt(struct rockchip_pcie *rockchip)
 		return PTR_ERR(rockchip->aclk_rst);
 	}
 
-	if (rockchip->is_rc) {
-		rockchip->ep_gpio = devm_gpiod_get_optional(dev, "ep",
-							    GPIOD_OUT_HIGH);
-		if (IS_ERR(rockchip->ep_gpio))
-			return dev_err_probe(dev, PTR_ERR(rockchip->ep_gpio),
-					     "failed to get ep GPIO\n");
-	}
+	rockchip->ep_gpio = devm_gpiod_get_optional(dev, "ep",
+				rockchip->is_rc ? GPIOD_OUT_HIGH : GPIOD_IN);
+	if (IS_ERR(rockchip->ep_gpio))
+		return dev_err_probe(dev, PTR_ERR(rockchip->ep_gpio),
+				     "failed to get ep GPIO\n");
 
 	rockchip->aclk_pcie = devm_clk_get(dev, "aclk");
 	if (IS_ERR(rockchip->aclk_pcie)) {
-- 
2.44.0