mfd / platform: cros_ec: Handle chained ECs as platform devices

An MFD is a device that contains several sub-devices (cells). For instance,
the ChromeOS EC fits in this description as usually contains a charger and
can have other devices with different functions like a Real-Time Clock,
an Audio codec, a Real-Time Clock, ...

If you look at the driver, though, we're doing something odd. We have
two MFD cros-ec drivers where one of them (cros-ec-core) instantiates
another MFD driver as sub-driver (cros-ec-dev), and the latest
instantiates the different sub-devices (Real-Time Clock, Audio codec,
etc).

                  MFD
------------------------------------------
   cros-ec-core
       |___ mfd-cellA (cros-ec-dev)
       |       |__ mfd-cell0
       |       |__ mfd-cell1
       |       |__ ...
       |
       |___ mfd-cellB (cros-ec-dev)
               |__ mfd-cell0
               |__ mfd-cell1
               |__ ...

The problem that was trying to solve is to describe some kind of topology for
the case where we have an EC (cros-ec) chained with another EC
(cros-pd). Apart from that this extends the bounds of what MFD was
designed to do we might be interested on have other kinds of topology that
can't be implemented in that way.

Let's prepare the code to move the cros-ec-core part from MFD to
platform/chrome as this is clearly a platform specific thing non-related
to a MFD device.

  platform/chrome  |         MFD
------------------------------------------
                   |
   cros-ec ________|___ cros-ec-dev
                   |       |__ mfd-cell0
                   |       |__ mfd-cell1
                   |       |__ ...
                   |
   cros-pd ________|___ cros-ec-dev
                   |        |__ mfd-cell0
                   |        |__ mfd-cell1
                   |        |__ ...
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
Tested-by: Gwendal Grignou <gwendal@chromium.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/cros_ec.c

@@ -13,7 +13,6 @@
 #include <linux/interrupt.h>
 #include <linux/slab.h>
 #include <linux/module.h>
-#include <linux/mfd/core.h>
 #include <linux/mfd/cros_ec.h>
 #include <linux/suspend.h>
 #include <asm/unaligned.h>
@@ -31,18 +30,6 @@ static struct cros_ec_platform pd_p = {
 	.cmd_offset = EC_CMD_PASSTHRU_OFFSET(CROS_EC_DEV_PD_INDEX),
 };
 
-static const struct mfd_cell ec_cell = {
-	.name = "cros-ec-dev",
-	.platform_data = &ec_p,
-	.pdata_size = sizeof(ec_p),
-};
-
-static const struct mfd_cell ec_pd_cell = {
-	.name = "cros-ec-dev",
-	.platform_data = &pd_p,
-	.pdata_size = sizeof(pd_p),
-};
-
 static irqreturn_t ec_irq_thread(int irq, void *data)
 {
 	struct cros_ec_device *ec_dev = data;
@@ -154,38 +141,42 @@ int cros_ec_register(struct cros_ec_device *ec_dev)
 		}
 	}
 
-	err = devm_mfd_add_devices(ec_dev->dev, PLATFORM_DEVID_AUTO, &ec_cell,
-				   1, NULL, ec_dev->irq, NULL);
-	if (err) {
-		dev_err(dev,
-			"Failed to register Embedded Controller subdevice %d\n",
-			err);
-		return err;
+	/* Register a platform device for the main EC instance */
+	ec_dev->ec = platform_device_register_data(ec_dev->dev, "cros-ec-dev",
+					PLATFORM_DEVID_AUTO, &ec_p,
+					sizeof(struct cros_ec_platform));
+	if (IS_ERR(ec_dev->ec)) {
+		dev_err(ec_dev->dev,
+			"Failed to create CrOS EC platform device\n");
+		return PTR_ERR(ec_dev->ec);
 	}
 
 	if (ec_dev->max_passthru) {
 		/*
-		 * Register a PD device as well on top of this device.
+		 * Register a platform device for the PD behind the main EC.
 		 * We make the following assumptions:
 		 * - behind an EC, we have a pd
 		 * - only one device added.
 		 * - the EC is responsive at init time (it is not true for a
-		 *   sensor hub.
+		 *   sensor hub).
 		 */
-		err = devm_mfd_add_devices(ec_dev->dev, PLATFORM_DEVID_AUTO,
-				      &ec_pd_cell, 1, NULL, ec_dev->irq, NULL);
-		if (err) {
-			dev_err(dev,
-				"Failed to register Power Delivery subdevice %d\n",
-				err);
-			return err;
+		ec_dev->pd = platform_device_register_data(ec_dev->dev,
+					"cros-ec-dev",
+					PLATFORM_DEVID_AUTO, &pd_p,
+					sizeof(struct cros_ec_platform));
+		if (IS_ERR(ec_dev->pd)) {
+			dev_err(ec_dev->dev,
+				"Failed to create CrOS PD platform device\n");
+			platform_device_unregister(ec_dev->ec);
+			return PTR_ERR(ec_dev->pd);
 		}
 	}
 
 	if (IS_ENABLED(CONFIG_OF) && dev->of_node) {
 		err = devm_of_platform_populate(dev);
 		if (err) {
-			mfd_remove_devices(dev);
+			platform_device_unregister(ec_dev->pd);
+			platform_device_unregister(ec_dev->ec);
 			dev_err(dev, "Failed to register sub-devices\n");
 			return err;
 		}
@@ -206,6 +197,16 @@ int cros_ec_register(struct cros_ec_device *ec_dev)
 }
 EXPORT_SYMBOL(cros_ec_register);
 
+int cros_ec_unregister(struct cros_ec_device *ec_dev)
+{
+	if (ec_dev->pd)
+		platform_device_unregister(ec_dev->pd);
+	platform_device_unregister(ec_dev->ec);
+
+	return 0;
+}
+EXPORT_SYMBOL(cros_ec_unregister);
+
 #ifdef CONFIG_PM_SLEEP
 int cros_ec_suspend(struct cros_ec_device *ec_dev)
 {

drivers/platform/chrome/cros_ec_i2c.c

@@ -307,6 +307,13 @@ static int cros_ec_i2c_probe(struct i2c_client *client,
 	return 0;
 }
 
+static int cros_ec_i2c_remove(struct i2c_client *client)
+{
+	struct cros_ec_device *ec_dev = i2c_get_clientdata(client);
+
+	return cros_ec_unregister(ec_dev);
+}
+
 #ifdef CONFIG_PM_SLEEP
 static int cros_ec_i2c_suspend(struct device *dev)
 {
@@ -357,6 +364,7 @@ static struct i2c_driver cros_ec_driver = {
 		.pm	= &cros_ec_i2c_pm_ops,
 	},
 	.probe		= cros_ec_i2c_probe,
+	.remove		= cros_ec_i2c_remove,
 	.id_table	= cros_ec_i2c_id,
 };
 

drivers/platform/chrome/cros_ec_lpc.c

@@ -421,6 +421,7 @@ static int cros_ec_lpc_probe(struct platform_device *pdev)
 
 static int cros_ec_lpc_remove(struct platform_device *pdev)
 {
+	struct cros_ec_device *ec_dev = platform_get_drvdata(pdev);
 	struct acpi_device *adev;
 
 	adev = ACPI_COMPANION(&pdev->dev);
@@ -428,7 +429,7 @@ static int cros_ec_lpc_remove(struct platform_device *pdev)
 		acpi_remove_notify_handler(adev->handle, ACPI_ALL_NOTIFY,
 					   cros_ec_lpc_acpi_notify);
 
-	return 0;
+	return cros_ec_unregister(ec_dev);
 }
 
 static const struct acpi_device_id cros_ec_lpc_acpi_device_ids[] = {

drivers/platform/chrome/cros_ec_rpmsg.c

@@ -233,6 +233,8 @@ static void cros_ec_rpmsg_remove(struct rpmsg_device *rpdev)
 	struct cros_ec_device *ec_dev = dev_get_drvdata(&rpdev->dev);
 	struct cros_ec_rpmsg *ec_rpmsg = ec_dev->priv;
 
+	cros_ec_unregister(ec_dev);
+
 	cancel_work_sync(&ec_rpmsg->host_event_work);
 }
 

drivers/platform/chrome/cros_ec_spi.c

@@ -785,6 +785,13 @@ static int cros_ec_spi_probe(struct spi_device *spi)
 	return 0;
 }
 
+static int cros_ec_spi_remove(struct spi_device *spi)
+{
+	struct cros_ec_device *ec_dev = spi_get_drvdata(spi);
+
+	return cros_ec_unregister(ec_dev);
+}
+
 #ifdef CONFIG_PM_SLEEP
 static int cros_ec_spi_suspend(struct device *dev)
 {
@@ -823,6 +830,7 @@ static struct spi_driver cros_ec_driver_spi = {
 		.pm	= &cros_ec_spi_pm_ops,
 	},
 	.probe		= cros_ec_spi_probe,
+	.remove		= cros_ec_spi_remove,
 	.id_table	= cros_ec_spi_id,
 };
 

include/linux/mfd/cros_ec.h

@@ -121,6 +121,10 @@ struct cros_ec_command {
  * @event_data: Raw payload transferred with the MKBP event.
  * @event_size: Size in bytes of the event data.
  * @host_event_wake_mask: Mask of host events that cause wake from suspend.
+ * @ec: The platform_device used by the mfd driver to interface with the
+ *      main EC.
+ * @pd: The platform_device used by the mfd driver to interface with the
+ *      PD behind an EC.
  */
 struct cros_ec_device {
 	/* These are used by other drivers that want to talk to the EC */
@@ -157,6 +161,10 @@ struct cros_ec_device {
 	int event_size;
 	u32 host_event_wake_mask;
 	u32 last_resume_result;
+
+	/* The platform devices used by the mfd driver */
+	struct platform_device *ec;
+	struct platform_device *pd;
 };
 
 /**
@@ -291,6 +299,16 @@ int cros_ec_cmd_xfer_status(struct cros_ec_device *ec_dev,
  */
 int cros_ec_register(struct cros_ec_device *ec_dev);
 
+/**
+ * cros_ec_unregister() - Remove a ChromeOS EC.
+ * @ec_dev: Device to unregister.
+ *
+ * Call this to deregister a ChromeOS EC, then clean up any private data.
+ *
+ * Return: 0 on success or negative error code.
+ */
+int cros_ec_unregister(struct cros_ec_device *ec_dev);
+
 /**
  * cros_ec_query_all() -  Query the protocol version supported by the
  *         ChromeOS EC.