firmware: xilinx: Add debugfs interface

Firmware-debug provides debugfs interface to all APIs.
Debugfs can be used to call firmware APIs with required
parameters.

Usage:
* Calling firmware API through debugfs:
# echo "<api-name> <arg1> .. <argn>" > /sys/.../zynqmp-firmware/pm

* Read output of last called firmware API:
# cat /sys/.../zynqmp-firmware/pm

Refer ug1200 for more information on these APIs:
* https://www.xilinx.com/support/documentation/user_guides/ug1200-eemi-api.pdf

Add basic debugfs file to get API version.

Signed-off-by: Rajan Vaja <[e-mail]>
Signed-off-by: Jolly Shah <[e-mail]>
Signed-off-by: Michal Simek <[e-mail]>

drivers/firmware/xilinx/Kconfig

···
 	  Say yes to enable ZynqMP firmware interface driver.
 	  If in doubt, say N.
 
+config ZYNQMP_FIRMWARE_DEBUG
+	bool "Enable Xilinx Zynq MPSoC firmware debug APIs"
+	depends on ZYNQMP_FIRMWARE && DEBUG_FS
+	help
+	  Say yes to enable ZynqMP firmware interface debug APIs.
+	  If in doubt, say N.
+
 endmenu

drivers/firmware/xilinx/Makefile

···
 # Makefile for Xilinx firmwares
 
 obj-$(CONFIG_ZYNQMP_FIRMWARE) += zynqmp.o
+obj-$(CONFIG_ZYNQMP_FIRMWARE_DEBUG) += zynqmp-debug.o

drivers/firmware/xilinx/zynqmp-debug.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Xilinx Zynq MPSoC Firmware layer for debugfs APIs
+ *
+ *  Copyright (C) 2014-2018 Xilinx, Inc.
+ *
+ *  Michal Simek <[e-mail]>
+ *  Davorin Mista <[e-mail]>
+ *  Jolly Shah <[e-mail]>
+ *  Rajan Vaja <[e-mail]>
+ */
+
+#include <linux/compiler.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/debugfs.h>
+#include <linux/uaccess.h>
+
+#include <linux/firmware/xlnx-zynqmp.h>
+#include "zynqmp-debug.h"
+
+#define PM_API_NAME_LEN			50
+
+struct pm_api_info {
+	u32 api_id;
+	char api_name[PM_API_NAME_LEN];
+	char api_name_len;
+};
+
+static char debugfs_buf[PAGE_SIZE];
+
+#define PM_API(id)		 {id, #id, strlen(#id)}
+static struct pm_api_info pm_api_list[] = {
+	PM_API(PM_GET_API_VERSION),
+};
+
+struct dentry *firmware_debugfs_root;
+
+/**
+ * zynqmp_pm_argument_value() - Extract argument value from a PM-API request
+ * @arg:	Entered PM-API argument in string format
+ *
+ * Return: Argument value in unsigned integer format on success
+ *	   0 otherwise
+ */
+static u64 zynqmp_pm_argument_value(char *arg)
+{
+	u64 value;
+
+	if (!arg)
+		return 0;
+
+	if (!kstrtou64(arg, 0, &value))
+		return value;
+
+	return 0;
+}
+
+/**
+ * get_pm_api_id() - Extract API-ID from a PM-API request
+ * @pm_api_req:		Entered PM-API argument in string format
+ * @pm_id:		API-ID
+ *
+ * Return: 0 on success else error code
+ */
+static int get_pm_api_id(char *pm_api_req, u32 *pm_id)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(pm_api_list) ; i++) {
+		if (!strncasecmp(pm_api_req, pm_api_list[i].api_name,
+				 pm_api_list[i].api_name_len)) {
+			*pm_id = pm_api_list[i].api_id;
+			break;
+		}
+	}
+
+	/* If no name was entered look for PM-API ID instead */
+	if (i == ARRAY_SIZE(pm_api_list) && kstrtouint(pm_api_req, 10, pm_id))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int process_api_request(u32 pm_id, u64 *pm_api_arg, u32 *pm_api_ret)
+{
+	const struct zynqmp_eemi_ops *eemi_ops = zynqmp_pm_get_eemi_ops();
+	u32 pm_api_version;
+	int ret;
+
+	if (!eemi_ops)
+		return -ENXIO;
+
+	switch (pm_id) {
+	case PM_GET_API_VERSION:
+		ret = eemi_ops->get_api_version(&pm_api_version);
+		sprintf(debugfs_buf, "PM-API Version = %d.%d\n",
+			pm_api_version >> 16, pm_api_version & 0xffff);
+		break;
+	default:
+		sprintf(debugfs_buf, "Unsupported PM-API request\n");
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+/**
+ * zynqmp_pm_debugfs_api_write() - debugfs write function
+ * @file:	User file
+ * @ptr:	User entered PM-API string
+ * @len:	Length of the userspace buffer
+ * @off:	Offset within the file
+ *
+ * Used for triggering pm api functions by writing
+ * echo <pm_api_id>	> /sys/kernel/debug/zynqmp_pm/power or
+ * echo <pm_api_name>	> /sys/kernel/debug/zynqmp_pm/power
+ *
+ * Return: Number of bytes copied if PM-API request succeeds,
+ *	   the corresponding error code otherwise
+ */
+static ssize_t zynqmp_pm_debugfs_api_write(struct file *file,
+					   const char __user *ptr, size_t len,
+					   loff_t *off)
+{
+	char *kern_buff, *tmp_buff;
+	char *pm_api_req;
+	u32 pm_id = 0;
+	u64 pm_api_arg[4] = {0, 0, 0, 0};
+	/* Return values from PM APIs calls */
+	u32 pm_api_ret[4] = {0, 0, 0, 0};
+
+	int ret;
+	int i = 0;
+
+	strcpy(debugfs_buf, "");
+
+	if (*off != 0 || len == 0)
+		return -EINVAL;
+
+	kern_buff = kzalloc(len, GFP_KERNEL);
+	if (!kern_buff)
+		return -ENOMEM;
+
+	tmp_buff = kern_buff;
+
+	ret = strncpy_from_user(kern_buff, ptr, len);
+	if (ret < 0) {
+		ret = -EFAULT;
+		goto err;
+	}
+
+	/* Read the API name from a user request */
+	pm_api_req = strsep(&kern_buff, " ");
+
+	ret = get_pm_api_id(pm_api_req, &pm_id);
+	if (ret < 0)
+		goto err;
+
+	/* Read node_id and arguments from the PM-API request */
+	pm_api_req = strsep(&kern_buff, " ");
+	while ((i < ARRAY_SIZE(pm_api_arg)) && pm_api_req) {
+		pm_api_arg[i++] = zynqmp_pm_argument_value(pm_api_req);
+		pm_api_req = strsep(&kern_buff, " ");
+	}
+
+	ret = process_api_request(pm_id, pm_api_arg, pm_api_ret);
+
+err:
+	kfree(tmp_buff);
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+/**
+ * zynqmp_pm_debugfs_api_read() - debugfs read function
+ * @file:	User file
+ * @ptr:	Requested pm_api_version string
+ * @len:	Length of the userspace buffer
+ * @off:	Offset within the file
+ *
+ * Return: Length of the version string on success
+ *	   else error code
+ */
+static ssize_t zynqmp_pm_debugfs_api_read(struct file *file, char __user *ptr,
+					  size_t len, loff_t *off)
+{
+	return simple_read_from_buffer(ptr, len, off, debugfs_buf,
+				       strlen(debugfs_buf));
+}
+
+/* Setup debugfs fops */
+static const struct file_operations fops_zynqmp_pm_dbgfs = {
+	.owner = THIS_MODULE,
+	.write = zynqmp_pm_debugfs_api_write,
+	.read = zynqmp_pm_debugfs_api_read,
+};
+
+/**
+ * zynqmp_pm_api_debugfs_init - Initialize debugfs interface
+ *
+ * Return:	None
+ */
+void zynqmp_pm_api_debugfs_init(void)
+{
+	/* Initialize debugfs interface */
+	firmware_debugfs_root = debugfs_create_dir("zynqmp-firmware", NULL);
+	debugfs_create_file("pm", 0660, firmware_debugfs_root, NULL,
+			    &fops_zynqmp_pm_dbgfs);
+}
+
+/**
+ * zynqmp_pm_api_debugfs_exit - Remove debugfs interface
+ *
+ * Return:	None
+ */
+void zynqmp_pm_api_debugfs_exit(void)
+{
+	debugfs_remove_recursive(firmware_debugfs_root);
+}

drivers/firmware/xilinx/zynqmp-debug.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Xilinx Zynq MPSoC Firmware layer
+ *
+ *  Copyright (C) 2014-2018 Xilinx
+ *
+ *  Michal Simek <[e-mail]>
+ *  Davorin Mista <[e-mail]>
+ *  Jolly Shah <[e-mail]>
+ *  Rajan Vaja <[e-mail]>
+ */
+
+#ifndef __FIRMWARE_ZYNQMP_DEBUG_H__
+#define __FIRMWARE_ZYNQMP_DEBUG_H__
+
+#if IS_REACHABLE(CONFIG_ZYNQMP_FIRMWARE_DEBUG)
+void zynqmp_pm_api_debugfs_init(void);
+void zynqmp_pm_api_debugfs_exit(void);
+#else
+static inline void zynqmp_pm_api_debugfs_init(void) { }
+static inline void zynqmp_pm_api_debugfs_exit(void) { }
+#endif
+
+#endif /* __FIRMWARE_ZYNQMP_DEBUG_H__ */

drivers/firmware/xilinx/zynqmp.c

···
 #include <linux/uaccess.h>
 
 #include <linux/firmware/xlnx-zynqmp.h>
+#include "zynqmp-debug.h"
 
 /**
  * zynqmp_pm_ret_code() - Convert PMU-FW error codes to Linux error codes
···
 	pr_info("%s Trustzone version v%d.%d\n", __func__,
 		pm_tz_version >> 16, pm_tz_version & 0xFFFF);
 
+	zynqmp_pm_api_debugfs_init();
+
 	return of_platform_populate(dev->of_node, NULL, NULL, dev);
 }
 
 static int zynqmp_firmware_remove(struct platform_device *pdev)
 {
+	zynqmp_pm_api_debugfs_exit();
+
 	return 0;
 }