[PATCH v3 09/10] thermal: Add PCIe cooling driver

Ilpo Järvinen
2023-09-29T11:59:50Z

Add a thermal cooling driver to provide path to access PCIe bandwidth
controller using the usual thermal interfaces.

A cooling device is instantiated for controllable PCIe ports from the
bwctrl service driver.

The thermal side state 0 means no throttling, i.e., maximum supported
PCIe speed.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael@kernel.org> # From the cooling device interface perspective
---
MAINTAINERS | 1 +
drivers/pci/pcie/bwctrl.c | 11 ++++
drivers/thermal/Kconfig | 10 +++
drivers/thermal/Makefile | 2 +
drivers/thermal/pcie_cooling.c | 107 +++++++++++++++++++++++++++++++++
include/linux/pci-bwctrl.h | 16 +++++
6 files changed, 147 insertions(+)
create mode 100644 drivers/thermal/pcie_cooling.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 2e4ad074eaf3..40dd7c0b154d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -16574,6 +16574,7 @@ M: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
L: linux-pci@vger.kernel.org
S: Supported
F: drivers/pci/pcie/bwctrl.c
+F: drivers/thermal/pcie_cooling.c
F: include/linux/pci-bwctrl.h

PCIE DRIVER FOR AMAZON ANNAPURNA LABS
diff --git a/drivers/pci/pcie/bwctrl.c b/drivers/pci/pcie/bwctrl.c
index e3172d69476f..13c73546244e 100644
--- a/drivers/pci/pcie/bwctrl.c
+++ b/drivers/pci/pcie/bwctrl.c
@@ -34,9 +34,11 @@
/**
* struct bwctrl_service_data - PCIe Port Bandwidth Controller
* @set_speed_mutex: serializes link speed changes
+ * @cdev: thermal cooling device associated with the port
*/
struct bwctrl_service_data {
struct mutex set_speed_mutex;
+ struct thermal_cooling_device *cdev;
};

static bool bwctrl_valid_pcie_speed(enum pci_bus_speed speed)
@@ -253,8 +255,16 @@ static int pcie_bandwidth_notification_probe(struct pcie_device *srv)
pcie_enable_link_bandwidth_notification(port);
pci_info(port, "enabled with IRQ %d\n", srv->irq);

+ data->cdev = pcie_cooling_device_register(port, srv);
+ if (IS_ERR(data->cdev)) {
+ ret = PTR_ERR(data->cdev);
+ goto disable_notifications;
+ }
return 0;

+disable_notifications:
+ pcie_disable_link_bandwidth_notification(srv->port);
+ kfree(data);
free_irq:
free_irq(srv->irq, srv);
return ret;
@@ -264,6 +274,7 @@ static void pcie_bandwidth_notification_remove(struct pcie_device *srv)
{
struct bwctrl_service_data *data = get_service_data(srv);

+ pcie_cooling_device_unregister(data->cdev);
pcie_disable_link_bandwidth_notification(srv->port);
free_irq(srv->irq, srv);
mutex_destroy(&data->set_speed_mutex);
diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
index c81a00fbca7d..3a071396f1c6 100644
--- a/drivers/thermal/Kconfig
+++ b/drivers/thermal/Kconfig
@@ -219,6 +219,16 @@ config DEVFREQ_THERMAL

If you want this support, you should say Y here.

+config PCIE_THERMAL
+ bool "PCIe cooling support"
+ depends on PCIEPORTBUS
+ select PCIE_BW
+ help
+ This implements PCIe cooling mechanism through bandwidth reduction
+ for PCIe devices.
+
+ If you want this support, you should say Y here.
+
config THERMAL_EMULATION
bool "Thermal emulation mode support"
help
diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
index c934cab309ae..a0b25a2742b7 100644
--- a/drivers/thermal/Makefile
+++ b/drivers/thermal/Makefile
@@ -30,6 +30,8 @@ thermal_sys-$(CONFIG_CPU_IDLE_THERMAL) += cpuidle_cooling.o
# devfreq cooling
thermal_sys-$(CONFIG_DEVFREQ_THERMAL) += devfreq_cooling.o

+thermal_sys-$(CONFIG_PCIE_THERMAL) += pcie_cooling.o
+
obj-$(CONFIG_K3_THERMAL) += k3_bandgap.o k3_j72xx_bandgap.o
# platform thermal drivers
obj-y += broadcom/
diff --git a/drivers/thermal/pcie_cooling.c b/drivers/thermal/pcie_cooling.c
new file mode 100644
index 000000000000..c23b59dd0331
--- /dev/null
+++ b/drivers/thermal/pcie_cooling.c
@@ -0,0 +1,107 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * PCIe cooling device
+ *
+ * Copyright (C) 2023 Intel Corporation.
+ */
+
+#include <linux/build_bug.h>
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/pci.h>
+#include <linux/pci-bwctrl.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/thermal.h>
+
+#define COOLING_DEV_TYPE_PREFIX "PCIe_Port_Link_Speed_"
+
+struct pcie_cooling_device {
+ struct pci_dev *port;
+ struct pcie_device *pdev;
+};
+
+static int pcie_cooling_get_max_level(struct thermal_cooling_device *cdev, unsigned long *state)
+{
+ struct pcie_cooling_device *pcie_cdev = cdev->devdata;
+
+ /* cooling state 0 is same as the maximum PCIe speed */
+ *state = pcie_cdev->port->subordinate->max_bus_speed - PCIE_SPEED_2_5GT;
+
+ return 0;
+}
+
+static int pcie_cooling_get_cur_level(struct thermal_cooling_device *cdev, unsigned long *state)
+{
+ struct pcie_cooling_device *pcie_cdev = cdev->devdata;
+
+ /* cooling state 0 is same as the maximum PCIe speed */
+ *state = cdev->max_state -
+ (pcie_cdev->port->subordinate->cur_bus_speed - PCIE_SPEED_2_5GT);
+
+ return 0;
+}
+
+static int pcie_cooling_set_cur_level(struct thermal_cooling_device *cdev, unsigned long state)
+{
+ struct pcie_cooling_device *pcie_cdev = cdev->devdata;
+ enum pci_bus_speed speed;
+
+ /* cooling state 0 is same as the maximum PCIe speed */
+ speed = (cdev->max_state - state) + PCIE_SPEED_2_5GT;
+
+ return bwctrl_set_current_speed(pcie_cdev->pdev, speed);
+}
+
+static struct thermal_cooling_device_ops pcie_cooling_ops = {
+ .get_max_state = pcie_cooling_get_max_level,
+ .get_cur_state = pcie_cooling_get_cur_level,
+ .set_cur_state = pcie_cooling_set_cur_level,
+};
+
+struct thermal_cooling_device *pcie_cooling_device_register(struct pci_dev *port,
+ struct pcie_device *pdev)
+{
+ struct pcie_cooling_device *pcie_cdev;
+ struct thermal_cooling_device *cdev;
+ size_t name_len;
+ char *name;
+
+ pcie_cdev = kzalloc(sizeof(*pcie_cdev), GFP_KERNEL);
+ if (!pcie_cdev)
+ return ERR_PTR(-ENOMEM);
+
+ pcie_cdev->port = port;
+ pcie_cdev->pdev = pdev;
+
+ name_len = strlen(COOLING_DEV_TYPE_PREFIX) + strlen(pci_name(port)) + 1;
+ name = kzalloc(name_len, GFP_KERNEL);
+ if (!name) {
+ kfree(pcie_cdev);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ snprintf(name, name_len, COOLING_DEV_TYPE_PREFIX "%s", pci_name(port));
+ cdev = thermal_cooling_device_register(name, pcie_cdev, &pcie_cooling_ops);
+ kfree(name);
+
+ return cdev;
+}
+
+void pcie_cooling_device_unregister(struct thermal_cooling_device *cdev)
+{
+ struct pcie_cooling_device *pcie_cdev = cdev->devdata;
+
+ thermal_cooling_device_unregister(cdev);
+ kfree(pcie_cdev);
+}
+
+/* For bus_speed <-> state arithmetic */
+static_assert(PCIE_SPEED_2_5GT + 1 == PCIE_SPEED_5_0GT);
+static_assert(PCIE_SPEED_5_0GT + 1 == PCIE_SPEED_8_0GT);
+static_assert(PCIE_SPEED_8_0GT + 1 == PCIE_SPEED_16_0GT);
+static_assert(PCIE_SPEED_16_0GT + 1 == PCIE_SPEED_32_0GT);
+static_assert(PCIE_SPEED_32_0GT + 1 == PCIE_SPEED_64_0GT);
+
+MODULE_AUTHOR("Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>");
+MODULE_DESCRIPTION("PCIe cooling driver");
diff --git a/include/linux/pci-bwctrl.h b/include/linux/pci-bwctrl.h
index 8eae09bd03b5..366445517b72 100644
--- a/include/linux/pci-bwctrl.h
+++ b/include/linux/pci-bwctrl.h
@@ -11,7 +11,23 @@
#include <linux/pci.h>

struct pcie_device;
+struct thermal_cooling_device;

int bwctrl_set_current_speed(struct pcie_device *srv, enum pci_bus_speed speed);

+#ifdef CONFIG_PCIE_THERMAL
+struct thermal_cooling_device *pcie_cooling_device_register(struct pci_dev *port,
+ struct pcie_device *pdev);
+void pcie_cooling_device_unregister(struct thermal_cooling_device *cdev);
+#else
+static inline struct thermal_cooling_device *pcie_cooling_device_register(struct pci_dev *port,
+ struct pcie_device *pdev)
+{
+ return NULL;
+}
+static inline void pcie_cooling_device_unregister(struct thermal_cooling_device *cdev)
+{
+}
+#endif
+
#endif
--
2.30.2