[PATCH v3 6/7] misc: add ge-addon-connector driver

Luca Ceresoli
2024-08-09T15:35:53Z

Add a driver to support the runtime hot-pluggable add-on connector on the
GE SUNH device. This connector allows connecting and disconnecting an
add-on to/from the main device to augment its features. Connection and
disconnection can happen at runtime at any moment without notice.

Different add-on models can be connected, and each has an EEPROM with a
model identifier at a fixed address.

The add-on hardware is added and removed using device tree overlay loading
and unloading.

Co-developed-by: Herve Codina <herve.codina@bootlin.com>
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

---

Changed in v3:
- update to the new overlay representation that now does not include the
target node; instead the target node is the connector node itself and is
now passed by the connector driver to of_overlay_fdt_apply(), so the
overlay is now decoupled from the base device tree
- update to explicitely probe devices not reachable by the CPU on any
physical bus (which probe as platform devices) which are now inside a
'nobus-devices' subnode of the connector node
- change how the DRM bridge is populated to use the new device tree
representation, having the video ports inside the 'dsi' node

**NOTE** this specific change opens up a question about the
.of_node_reused flag: setting it to true might be wrong now as
the bridge will be handed the 'dsi' subnode of the connector
node; however not setting it to true prevents the hotplug
bridge module autoloading due to the alias string changing from
"platform:hotplug-dsi-bridge" to "of:NdsiT(null)".

- remove dev_info() and uninformative dev_dbg() calls
- Kconfig: use 'depends on' instead of 'select'
- Kconfig: improve help text and add module name

This patch first appeared in v2.
---
MAINTAINERS | 1 +
drivers/misc/Kconfig | 18 ++
drivers/misc/Makefile | 1 +
drivers/misc/ge-sunh-connector.c | 523 +++++++++++++++++++++++++++++++++++++++
4 files changed, 543 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index d571aa049ce1..021dfa961f3f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10262,6 +10262,7 @@ F: drivers/iio/pressure/mprls0025pa*
HOTPLUG CONNECTOR FOR GE SUNH ADDONS
M: Luca Ceresoli <luca.ceresoli@bootlin.com>
S: Maintained
+F: drivers/misc/ge-sunh-connector.c
F: Documentation/devicetree/bindings/connector/ge,sunh-addon-connector.yaml

HP BIOSCFG DRIVER
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 41c3d2821a78..8e4cc81b0ec9 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -600,6 +600,24 @@ config MARVELL_CN10K_DPI
To compile this driver as a module, choose M here: the module
will be called mrvl_cn10k_dpi.

+config GE_SUNH_CONNECTOR
+ tristate "GE SUNH hotplug add-on connector"
+ depends on OF_OVERLAY
+ depends on NVMEM
+ depends on DRM_HOTPLUG_BRIDGE
+ select FW_LOADER
+ help
+ Driver for the runtime hot-pluggable add-on connector on the GE
+ SUNH device. This connector allows connecting an add-on to the
+ main device to augment its features, and to later disconnect
+ it. Connection and disconnection can be done at runtime at any
+ moment without notice. Different add-on models can be connected,
+ and each has an EEPROM with a model identifier at a fixed
+ address.
+
+ To compile this driver as a module, choose M here.
+ The module will be called ge-sunh-connector.
+
source "drivers/misc/c2port/Kconfig"
source "drivers/misc/eeprom/Kconfig"
source "drivers/misc/cb710/Kconfig"
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index c2f990862d2b..69747b048046 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -70,4 +70,5 @@ obj-$(CONFIG_TPS6594_ESM) += tps6594-esm.o
obj-$(CONFIG_TPS6594_PFSM) += tps6594-pfsm.o
obj-$(CONFIG_NSM) += nsm.o
obj-$(CONFIG_MARVELL_CN10K_DPI) += mrvl_cn10k_dpi.o
+obj-$(CONFIG_GE_SUNH_CONNECTOR) += ge-sunh-connector.o
obj-y += keba/
diff --git a/drivers/misc/ge-sunh-connector.c b/drivers/misc/ge-sunh-connector.c
new file mode 100644
index 000000000000..50c9e35a60e3
--- /dev/null
+++ b/drivers/misc/ge-sunh-connector.c
@@ -0,0 +1,523 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * GE SUNH hotplug add-on connector
+ *
+ * Driver for the runtime hot-pluggable add-on connector on the GE SUNH
+ * device. Add-on connection is detected via GPIOs (+ a debugfs
+ * trigger). On connection, a "base" DT overlay is added that describes
+ * enough to reach the NVMEM cell with the model ID. Based on the ID, an
+ * add-on-specific overlay is loaded on top to describe everything else.
+ *
+ * Copyright (C) 2024, GE HealthCare
+ *
+ * Authors:
+ * Luca Ceresoli <luca.ceresoli@bootlin.com>
+ * Herve Codina <herve.codina@bootlin.com>
+ */
+
+#include <linux/debugfs.h>
+#include <linux/delay.h>
+#include <linux/firmware.h>
+#include <linux/gpio/consumer.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/nvmem-consumer.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/workqueue.h>
+
+enum sunh_conn_overlay_level {
+ SUNH_CONN_OVERLAY_BASE,
+ SUNH_CONN_OVERLAY_ADDON,
+ SUNH_CONN_OVERLAY_N_LEVELS
+};
+
+#define SUNH_CONN_N_STATUS_GPIOS 2
+static const char * const sunh_conn_status_gpio_name[SUNH_CONN_N_STATUS_GPIOS] = {
+ "plugged", "powergood"
+};
+
+struct sunh_conn {
+ struct device *dev;
+ struct gpio_desc *reset_gpio;
+ struct gpio_desc *status_gpio[SUNH_CONN_N_STATUS_GPIOS];
+
+ bool plugged;
+ int ovcs_id[SUNH_CONN_OVERLAY_N_LEVELS];
+ struct mutex ovl_mutex; // serialize overlay code
+ struct notifier_block nvmem_nb;
+ struct work_struct nvmem_notifier_work;
+
+ struct platform_device *hpb_pdev;
+ struct dentry *debugfs_root;
+};
+
+/*
+ * Populate all platform devices that are not on any bus.
+ *
+ * Populate devices without any I/O access from the CPU, (e.g. fixed
+ * regulators and gpio regulators). In the normal case of a device tree
+ * without runtime-loaded overlays these are direct children of the root
+ * node and as such they are populated as a special case.
+ *
+ * Within the hotplug connector they need to be at a deeper level of the
+ * tree. Moreover they are "segregated" in the "nobus-devices" node which
+ * allows to avoid trying of_platform_default_populate() on other kind of
+ * nodes.
+ *
+ * No need to depopulate them in this driver: of_platform_notify() will do
+ * that on overlay removal.
+ *
+ * In case a generalized framework for OF_based hotplug connector drivers
+ * will exist in the future, this function is definitely meant for the
+ * framework.
+ */
+static int sunh_conn_populate_nobus_devices(struct sunh_conn *conn)
+{
+ struct device_node *nobus_devs_dn;
+ int err;
+
+ nobus_devs_dn = of_get_child_by_name(conn->dev->of_node, "nobus-devices");
+ if (!nobus_devs_dn)
+ return 0;
+
+ err = of_platform_default_populate(nobus_devs_dn, NULL, conn->dev);
+ if (err)
+ dev_err(conn->dev, "Failed to populate nobus devices\n");
+
+ of_node_put(nobus_devs_dn);
+ return err;
+}
+
+static int sunh_conn_insert_overlay(struct sunh_conn *conn,
+ enum sunh_conn_overlay_level level,
+ const char *filename)
+{
+ const struct firmware *fw;
+ int err;
+
+ err = request_firmware(&fw, filename, conn->dev);
+ if (err)
+ return dev_err_probe(conn->dev, err, "Error requesting overlay %s", filename);
+
+ dev_dbg(conn->dev, "insert overlay %d: %s", level, filename);
+ err = of_overlay_fdt_apply(fw->data, fw->size, &conn->ovcs_id[level], conn->dev->of_node);
+ if (err)
+ dev_err_probe(conn->dev, err, "Failed to apply overlay %s\n", filename);
+ else
+ err = sunh_conn_populate_nobus_devices(conn);
+
+ if (err) {
+ int err2;
+
+ /* changeset may be partially applied */
+ err2 = of_overlay_remove(&conn->ovcs_id[level]);
+ if (err2 < 0)
+ dev_err_probe(conn->dev, err2,
+ "Failed to remove failed overlay %s\n", filename);
+ }
+
+ release_firmware(fw);
+
+ return err;
+}
+
+static int sunh_conn_load_base_overlay(struct sunh_conn *conn)
+{
+ int err = 0;
+
+ mutex_lock(&conn->ovl_mutex);
+
+ if (conn->ovcs_id[0] != 0) {
+ dev_dbg(conn->dev, "base overlay already loaded\n");
+ goto out_unlock;
+ }
+
+ err = sunh_conn_insert_overlay(conn, 0, "imx8mp-sundv1-addon-base.dtbo");
+
+out_unlock:
+ mutex_unlock(&conn->ovl_mutex);
+ return err;
+}
+
+static int sunh_conn_load_addon_overlay(struct sunh_conn *conn)
+{
+ u8 addon_id;
+ const char *filename;
+ int err;
+
+ mutex_lock(&conn->ovl_mutex);
+
+ if (conn->ovcs_id[0] == 0) {
+ dev_dbg(conn->dev, "base overlay not loaded\n");
+ err = -EINVAL;
+ goto out_unlock;
+ }
+
+ if (conn->ovcs_id[1] != 0) {
+ dev_dbg(conn->dev, "addon overlay already loaded\n");
+ err = -EEXIST;
+ goto out_unlock;
+ }
+
+ err = nvmem_cell_read_u8(conn->dev, "id", &addon_id);
+ if (err)
+ goto out_unlock;
+
+ dev_dbg(conn->dev, "Found add-on ID %d\n", addon_id);
+
+ switch (addon_id) {
+ case 23:
+ filename = "imx8mp-sundv1-addon-13.dtbo";
+ break;
+ case 24:
+ filename = "imx8mp-sundv1-addon-15.dtbo";
+ break;
+ case 25:
+ filename = "imx8mp-sundv1-addon-18.dtbo";
+ break;
+ default:
+ dev_warn(conn->dev, "Unknown add-on ID %d\n", addon_id);
+ err = -ENODEV;
+ goto out_unlock;
+ }
+
+ err = sunh_conn_insert_overlay(conn, 1, filename);
+
+out_unlock:
+ mutex_unlock(&conn->ovl_mutex);
+ return err;
+}
+
+static void sunh_conn_unload_overlays(struct sunh_conn *conn)
+{
+ int level = SUNH_CONN_OVERLAY_N_LEVELS;
+ int err;
+
+ mutex_lock(&conn->ovl_mutex);
+ while (level) {
+ level--;
+
+ if (conn->ovcs_id[level] == 0)
+ continue;
+
+ dev_dbg(conn->dev, "remove overlay %d (ovcs id %d)",
+ level, conn->ovcs_id[level]);
+
+ err = of_overlay_remove(&conn->ovcs_id[level]);
+ if (err)
+ dev_err_probe(conn->dev, err, "Failed to remove overlay %d\n", level);
+ }
+ mutex_unlock(&conn->ovl_mutex);
+}
+
+static void sunh_conn_reset(struct sunh_conn *conn, bool keep_reset)
+{
+ gpiod_set_value_cansleep(conn->reset_gpio, 1);
+
+ if (keep_reset)
+ return;
+
+ mdelay(10);
+ gpiod_set_value_cansleep(conn->reset_gpio, 0);
+ mdelay(10);
+}
+
+static int sunh_conn_detach(struct sunh_conn *conn)
+{
+ /* Cancel any pending NVMEM notification jobs */
+ cancel_work_sync(&conn->nvmem_notifier_work);
+
+ /* Unload previouly loaded overlays */
+ sunh_conn_unload_overlays(conn);
+
+ /* Set reset signal to have it set on next plug */
+ sunh_conn_reset(conn, true);
+
+ return 0;
+}
+
+static int sunh_conn_attach(struct sunh_conn *conn)
+{
+ int err;
+
+ /* Reset the plugged board in order to start from a stable state */
+ sunh_conn_reset(conn, false);
+
+ err = sunh_conn_load_base_overlay(conn);
+ if (err)
+ goto err;
+
+ /*
+ * -EPROBE_DEFER can be due to NVMEM cell not yet available, so
+ * don't give up, an NVMEM event could arrive later
+ */
+ err = sunh_conn_load_addon_overlay(conn);
+ if (err && err != -EPROBE_DEFER)
+ goto err;
+
+ return 0;
+
+err:
+ sunh_conn_detach(conn);
+ return err;
+}
+
+static int sunh_conn_handle_event(struct sunh_conn *conn, bool plugged)
+{
+ int err;
+
+ if (plugged == conn->plugged)
+ return 0;
+
+ dev_dbg(conn->dev, "%s\n", plugged ? "connected" : "disconnected");
+
+ err = (plugged ?
+ sunh_conn_attach(conn) :
+ sunh_conn_detach(conn));
+
+ conn->plugged = plugged;
+
+ return err;
+}
+
+/*
+ * Return the current status of the connector as reported by the hardware.
+ *
+ * Returns:
+ * - 0 if not connected (any of the existing status GPIOs not asserted) or
+ * no status GPIOs exist
+ * - 1 if connected in a stable manner (all status GPIOs are asserted)
+ * - a negative error code in case reading the GPIOs fail
+ */
+static int sunh_conn_get_connector_status(struct sunh_conn *conn)
+{
+ int status = 0;
+ int i;
+
+ for (i = 0; i < SUNH_CONN_N_STATUS_GPIOS; i++) {
+ int val;
+
+ if (!conn->status_gpio[i])
+ continue;
+
+ val = gpiod_get_value_cansleep(conn->status_gpio[i]);
+
+ if (val < 0) {
+ dev_err(conn->dev, "Error reading %s GPIO (%d)\n",
+ sunh_conn_status_gpio_name[i], val);
+ return val;
+ }
+
+ if (val == 0) {
+ dev_dbg(conn->dev, "%s GPIO deasserted\n",
+ sunh_conn_status_gpio_name[i]);
+ return 0;
+ }
+
+ status = 1;
+ }
+
+ return status;
+}
+
+static irqreturn_t sunh_conn_gpio_irq(int irq, void *data)
+{
+ struct sunh_conn *conn = data;
+ int conn_status;
+
+ conn_status = sunh_conn_get_connector_status(conn);
+ if (conn_status >= 0)
+ sunh_conn_handle_event(conn, conn_status);
+
+ return IRQ_HANDLED;
+}
+
+static int plugged_read(void *dat, u64 *val)
+{
+ struct sunh_conn *conn = dat;
+
+ *val = conn->plugged;
+
+ return 0;
+}
+
+static int plugged_write(void *dat, u64 val)
+{
+ struct sunh_conn *conn = dat;
+
+ if (val > 1)
+ return -EINVAL;
+
+ return sunh_conn_handle_event(conn, val);
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(plugged_fops, plugged_read, plugged_write, "%lld\n");
+
+static void sunh_conn_nvmem_notifier_work(struct work_struct *work)
+{
+ struct sunh_conn *conn = container_of(work, struct sunh_conn, nvmem_notifier_work);
+
+ sunh_conn_load_addon_overlay(conn);
+}
+
+static int sunh_conn_nvmem_notifier(struct notifier_block *nb, unsigned long action, void *arg)
+{
+ struct sunh_conn *conn = container_of(nb, struct sunh_conn, nvmem_nb);
+
+ if (action == NVMEM_CELL_ADD)
+ queue_work(system_power_efficient_wq, &conn->nvmem_notifier_work);
+
+ return NOTIFY_OK;
+}
+
+static int sunh_conn_register_drm_bridge(struct sunh_conn *conn)
+{
+ struct device *dev = conn->dev;
+ struct device_node *dsi_np;
+
+ dsi_np = of_get_child_by_name(dev->of_node, "dsi");
+ if (!dsi_np)
+ return dev_err_probe(dev, -ENOENT, "dsi node not found");
+
+ const struct platform_device_info hpb_info = {
+ .parent = dev,
+ .fwnode = of_fwnode_handle(dsi_np),
+ .of_node_reused = true,
+ .name = "hotplug-dsi-bridge",
+ .id = PLATFORM_DEVID_NONE,
+ };
+
+ conn->hpb_pdev = platform_device_register_full(&hpb_info);
+ of_node_put(dsi_np); // platform core gets/puts the device node
+ if (IS_ERR(conn->hpb_pdev))
+ return dev_err_probe(dev, PTR_ERR(conn->hpb_pdev),
+ "Error registering DRM bridge\n");
+
+ return 0;
+}
+
+static void sunh_conn_unregister_drm_bridge(struct sunh_conn *conn)
+{
+ platform_device_unregister(conn->hpb_pdev);
+}
+
+static int sunh_conn_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct sunh_conn *conn;
+ int conn_status;
+ int err;
+ int i;
+
+ /* Cannot load overlay from filesystem before rootfs is mounted */
+ if (system_state < SYSTEM_RUNNING)
+ return -EPROBE_DEFER;
+
+ conn = devm_kzalloc(dev, sizeof(*conn), GFP_KERNEL);
+ if (!conn)
+ return -ENOMEM;
+
+ platform_set_drvdata(pdev, conn);
+ conn->dev = dev;
+
+ mutex_init(&conn->ovl_mutex);
+ INIT_WORK(&conn->nvmem_notifier_work, sunh_conn_nvmem_notifier_work);
+
+ conn->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
+ if (IS_ERR(conn->reset_gpio))
+ return dev_err_probe(dev, PTR_ERR(conn->reset_gpio),
+ "Error getting reset GPIO\n");
+
+ for (i = 0; i < SUNH_CONN_N_STATUS_GPIOS; i++) {
+ conn->status_gpio[i] =
+ devm_gpiod_get_optional(dev, sunh_conn_status_gpio_name[i], GPIOD_IN);
+ if (IS_ERR(conn->status_gpio[i]))
+ return dev_err_probe(dev, PTR_ERR(conn->status_gpio[i]),
+ "Error getting %s GPIO\n",
+ sunh_conn_status_gpio_name[i]);
+ }
+
+ err = sunh_conn_register_drm_bridge(conn);
+ if (err)
+ return err;
+
+ conn->nvmem_nb.notifier_call = sunh_conn_nvmem_notifier;
+ err = nvmem_register_notifier(&conn->nvmem_nb);
+ if (err) {
+ dev_err_probe(dev, err, "Error registering NVMEM notifier\n");
+ goto err_unregister_drm_bridge;
+ }
+
+ for (i = 0; i < SUNH_CONN_N_STATUS_GPIOS; i++) {
+ if (conn->status_gpio[i]) {
+ err = devm_request_threaded_irq(dev, gpiod_to_irq(conn->status_gpio[i]),
+ NULL, sunh_conn_gpio_irq,
+ IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING |
+ IRQF_ONESHOT,
+ dev_name(dev), conn);
+ if (err) {
+ dev_err_probe(dev, err, "Error getting %s GPIO IRQ\n",
+ sunh_conn_status_gpio_name[i]);
+ goto err_nvmem_unregister_notifier;
+ }
+ }
+ }
+
+ conn_status = sunh_conn_get_connector_status(conn);
+ if (conn_status < 0) {
+ err = conn_status;
+ goto err_nvmem_unregister_notifier;
+ }
+
+ /* Ensure initial state is known and overlay loaded if plugged */
+ sunh_conn_handle_event(conn, conn_status);
+
+ conn->debugfs_root = debugfs_create_dir(dev_name(dev), NULL);
+ debugfs_create_file("plugged", 0644, conn->debugfs_root, conn, &plugged_fops);
+
+ return 0;
+
+err_nvmem_unregister_notifier:
+ nvmem_unregister_notifier(&conn->nvmem_nb);
+ cancel_work_sync(&conn->nvmem_notifier_work);
+err_unregister_drm_bridge:
+ sunh_conn_unregister_drm_bridge(conn);
+ return err;
+}
+
+static void sunh_conn_remove(struct platform_device *pdev)
+{
+ struct sunh_conn *conn = platform_get_drvdata(pdev);
+
+ debugfs_remove(conn->debugfs_root);
+ sunh_conn_detach(conn);
+
+ nvmem_unregister_notifier(&conn->nvmem_nb);
+ cancel_work_sync(&conn->nvmem_notifier_work);
+
+ sunh_conn_unregister_drm_bridge(conn);
+}
+
+static const struct of_device_id sunh_conn_dt_ids[] = {
+ { .compatible = "ge,sunh-addon-connector" },
+ {}
+};
+MODULE_DEVICE_TABLE(of, sunh_conn_dt_ids);
+
+static struct platform_driver sunh_conn_driver = {
+ .driver = {
+ .name = "sunh-addon-connector",
+ .of_match_table = sunh_conn_dt_ids,
+ },
+ .probe = sunh_conn_probe,
+ .remove_new = sunh_conn_remove,
+};
+module_platform_driver(sunh_conn_driver);
+
+MODULE_AUTHOR("Luca Ceresoli <luca.ceresoli@bootlin.com>");
+MODULE_AUTHOR("Herve Codina <herve.codina@bootlin.com>");
+MODULE_DESCRIPTION("GE SUNH hotplug add-on connector");
+MODULE_LICENSE("GPL");

--
2.34.1