[PATCH v3 12/12] PCI: rockchip-ep: Handle PERST# signal in endpoint mode

Damien Le Moal
2024-10-07T04:12:48Z

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 af50432525b4..c70a64c37a56 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;
};

@@ -462,13 +466,17 @@ 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;
}
@@ -478,6 +486,11 @@ 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 */
@@ -540,6 +553,13 @@ 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",
@@ -549,6 +569,7 @@ static void rockchip_pcie_ep_link_training(struct work_struct *work)

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

return;

@@ -556,6 +577,94 @@ 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,
@@ -719,6 +828,7 @@ 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)) {
@@ -751,7 +861,13 @@ 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_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 154e78819e6e..bcb1c9266c56 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_LOW);
- 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_LOW : 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)) {
--
2.46.2