[PATCH v5 13/14] PCI: rockchip-ep: Handle PERST# signal in endpoint mode

Damien Le Moal
2024-10-17T01:59:18Z

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

Modify the rockchip PCI endpoint controller driver to get the reset_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#.

Also, given that the host mode controller and the endpoint mode
controller use two different property names for the same PERST# signal
(ep_gpios property and reset_gpios property respectively), for clarity,
rename the ep_gpio field of struct rockchip_pcie to perst_gpio.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
---
drivers/pci/controller/pcie-rockchip-ep.c | 124 +++++++++++++++++++-
drivers/pci/controller/pcie-rockchip-host.c | 4 +-
drivers/pci/controller/pcie-rockchip.c | 16 +--
drivers/pci/controller/pcie-rockchip.h | 2 +-
4 files changed, 133 insertions(+), 13 deletions(-)

diff --git a/drivers/pci/controller/pcie-rockchip-ep.c b/drivers/pci/controller/pcie-rockchip-ep.c
index 43480706b8f4..19cfba5230a2 100644
--- a/drivers/pci/controller/pcie-rockchip-ep.c
+++ b/drivers/pci/controller/pcie-rockchip-ep.c
@@ -10,6 +10,7 @@

#include <linux/configfs.h>
#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
#include <linux/iopoll.h>
#include <linux/kernel.h>
#include <linux/of.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;
};

@@ -467,13 +471,17 @@ static int rockchip_pcie_ep_start(struct pci_epc *epc)

rockchip_pcie_write(rockchip, cfg, PCIE_CORE_PHY_FUNC_CFG);

+ if (rockchip->perst_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->perst_gpio)
+ schedule_delayed_work(&ep->link_training, 0);

return 0;
}
@@ -483,6 +491,11 @@ 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->perst_gpio) {
+ ep->perst_asserted = true;
+ disable_irq(ep->perst_irq);
+ }
+
cancel_delayed_work_sync(&ep->link_training);

/* Stop link training and disable configuration */
@@ -548,6 +561,13 @@ 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 (Negotiated speed: %sGT/s, width: x%lu)\n",
@@ -557,6 +577,7 @@ static void rockchip_pcie_ep_link_training(struct work_struct *work)

/* Notify the function */
pci_epc_linkup(ep->epc);
+ ep->link_up = true;

return;

@@ -564,6 +585,97 @@ 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;
+
+ dev_dbg(rockchip->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;
+
+ dev_dbg(rockchip->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->perst_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->perst_gpio)
+ return 0;
+
+ /* PCIe reset interrupt */
+ ep->perst_irq = gpiod_to_irq(rockchip->perst_gpio);
+ if (ep->perst_irq < 0) {
+ dev_err(dev, "No IRQ for PERST# GPIO\n");
+ return ep->perst_irq;
+ }
+
+ /*
+ * The perst_gpio is active low, so when it is inactive on start, it
+ * is high and will trigger the perst_irq handler. So treat this initial
+ * IRQ as a dummy one by faking the host asserting PERST#.
+ */
+ 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,
@@ -757,11 +869,17 @@ static int rockchip_pcie_ep_probe(struct platform_device *pdev)

pci_epc_init_notify(epc);

+ err = rockchip_pcie_ep_setup_irq(epc);
+ if (err < 0)
+ goto err_uninit_port;
+
return 0;
-err_exit_ob_mem:
- rockchip_pcie_ep_exit_ob_mem(ep);
+err_uninit_port:
+ rockchip_pcie_deinit_phys(rockchip);
err_disable_clocks:
rockchip_pcie_disable_clocks(rockchip);
+err_exit_ob_mem:
+ rockchip_pcie_ep_exit_ob_mem(ep);
return err;
}

diff --git a/drivers/pci/controller/pcie-rockchip-host.c b/drivers/pci/controller/pcie-rockchip-host.c
index cbec71114825..7471d9fd18bc 100644
--- a/drivers/pci/controller/pcie-rockchip-host.c
+++ b/drivers/pci/controller/pcie-rockchip-host.c
@@ -294,7 +294,7 @@ static int rockchip_pcie_host_init_port(struct rockchip_pcie *rockchip)
int err, i = MAX_LANE_NUM;
u32 status;

- gpiod_set_value_cansleep(rockchip->ep_gpio, 0);
+ gpiod_set_value_cansleep(rockchip->perst_gpio, 0);

err = rockchip_pcie_init_port(rockchip);
if (err)
@@ -323,7 +323,7 @@ static int rockchip_pcie_host_init_port(struct rockchip_pcie *rockchip)
PCIE_CLIENT_CONFIG);

msleep(PCIE_T_PVPERL_MS);
- gpiod_set_value_cansleep(rockchip->ep_gpio, 1);
+ gpiod_set_value_cansleep(rockchip->perst_gpio, 1);

msleep(PCIE_T_RRS_READY_MS);

diff --git a/drivers/pci/controller/pcie-rockchip.c b/drivers/pci/controller/pcie-rockchip.c
index 154e78819e6e..b9ade7632e11 100644
--- a/drivers/pci/controller/pcie-rockchip.c
+++ b/drivers/pci/controller/pcie-rockchip.c
@@ -119,13 +119,15 @@ 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_LOW);
- if (IS_ERR(rockchip->ep_gpio))
- return dev_err_probe(dev, PTR_ERR(rockchip->ep_gpio),
- "failed to get ep GPIO\n");
- }
+ if (rockchip->is_rc)
+ rockchip->perst_gpio = devm_gpiod_get_optional(dev, "ep",
+ GPIOD_OUT_LOW);
+ else
+ rockchip->perst_gpio = devm_gpiod_get_optional(dev, "reset",
+ GPIOD_IN);
+ if (IS_ERR(rockchip->perst_gpio))
+ return dev_err_probe(dev, PTR_ERR(rockchip->perst_gpio),
+ "failed to get PERST# GPIO\n");

rockchip->aclk_pcie = devm_clk_get(dev, "aclk");
if (IS_ERR(rockchip->aclk_pcie)) {
diff --git a/drivers/pci/controller/pcie-rockchip.h b/drivers/pci/controller/pcie-rockchip.h
index 24796176f658..a51b087ce878 100644
--- a/drivers/pci/controller/pcie-rockchip.h
+++ b/drivers/pci/controller/pcie-rockchip.h
@@ -329,7 +329,7 @@ struct rockchip_pcie {
struct regulator *vpcie3v3; /* 3.3V power supply */
struct regulator *vpcie1v8; /* 1.8V power supply */
struct regulator *vpcie0v9; /* 0.9V power supply */
- struct gpio_desc *ep_gpio;
+ struct gpio_desc *perst_gpio;
u32 lanes;
u8 lanes_map;
int link_gen;
--
2.47.0