1 files changed, 444 insertions, 0 deletions
diff --git a/drivers/misc/aspeed-p2a-ctrl.c b/drivers/misc/aspeed-p2a-ctrl.c
new file mode 100644
index 000000000000..b60fbeaffcbd
--- /dev/null
+++ b/drivers/misc/aspeed-p2a-ctrl.c
@@ -0,0 +1,444 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright 2019 Google Inc
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ * Provides a simple driver to control the ASPEED P2A interface which allows
+ * the host to read and write to various regions of the BMC's memory.
+ */
+
+#include <linux/fs.h>
+#include <linux/io.h>
+#include <linux/mfd/syscon.h>
+#include <linux/miscdevice.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of_address.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+#include <linux/aspeed-p2a-ctrl.h>
+
+#define DEVICE_NAME	"aspeed-p2a-ctrl"
+
+/* SCU2C is a Misc. Control Register. */
+#define SCU2C 0x2c
+/* SCU180 is the PCIe Configuration Setting Control Register. */
+#define SCU180 0x180
+/* Bit 1 controls the P2A bridge, while bit 0 controls the entire VGA device
+ * on the PCI bus.
+ */
+#define SCU180_ENP2A BIT(1)
+
+/* The ast2400/2500 both have six ranges. */
+#define P2A_REGION_COUNT 6
+
+struct region {
+	u64 min;
+	u64 max;
+	u32 bit;
+};
+
+struct aspeed_p2a_model_data {
+	/* min, max, bit */
+	struct region regions[P2A_REGION_COUNT];
+};
+
+struct aspeed_p2a_ctrl {
+	struct miscdevice miscdev;
+	struct regmap *regmap;
+
+	const struct aspeed_p2a_model_data *config;
+
+	/* Access to these needs to be locked, held via probe, mapping ioctl,
+	 * and release, remove.
+	 */
+	struct mutex tracking;
+	u32 readers;
+	u32 readerwriters[P2A_REGION_COUNT];
+
+	phys_addr_t mem_base;
+	resource_size_t mem_size;
+};
+
+struct aspeed_p2a_user {
+	struct file *file;
+	struct aspeed_p2a_ctrl *parent;
+
+	/* The entire memory space is opened for reading once the bridge is
+	 * enabled, therefore this needs only to be tracked once per user.
+	 * If any user has it open for read, the bridge must stay enabled.
+	 */
+	u32 read;
+
+	/* Each entry of the array corresponds to a P2A Region.  If the user
+	 * opens for read or readwrite, the reference goes up here.  On
+	 * release, this array is walked and references adjusted accordingly.
+	 */
+	u32 readwrite[P2A_REGION_COUNT];
+};
+
+static void aspeed_p2a_enable_bridge(struct aspeed_p2a_ctrl *p2a_ctrl)
+{
+	regmap_update_bits(p2a_ctrl->regmap,
+		SCU180, SCU180_ENP2A, SCU180_ENP2A);
+}
+
+static void aspeed_p2a_disable_bridge(struct aspeed_p2a_ctrl *p2a_ctrl)
+{
+	regmap_update_bits(p2a_ctrl->regmap, SCU180, SCU180_ENP2A, 0);
+}
+
+static int aspeed_p2a_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	unsigned long vsize;
+	pgprot_t prot;
+	struct aspeed_p2a_user *priv = file->private_data;
+	struct aspeed_p2a_ctrl *ctrl = priv->parent;
+
+	if (ctrl->mem_base == 0 && ctrl->mem_size == 0)
+		return -EINVAL;
+
+	vsize = vma->vm_end - vma->vm_start;
+	prot = vma->vm_page_prot;
+
+	if (vma->vm_pgoff + vsize > ctrl->mem_base + ctrl->mem_size)
+		return -EINVAL;
+
+	/* ast2400/2500 AHB accesses are not cache coherent */
+	prot = pgprot_noncached(prot);
+
+	if (remap_pfn_range(vma, vma->vm_start,
+		(ctrl->mem_base >> PAGE_SHIFT) + vma->vm_pgoff,
+		vsize, prot))
+		return -EAGAIN;
+
+	return 0;
+}
+
+static bool aspeed_p2a_region_acquire(struct aspeed_p2a_user *priv,
+		struct aspeed_p2a_ctrl *ctrl,
+		struct aspeed_p2a_ctrl_mapping *map)
+{
+	int i;
+	u64 base, end;
+	bool matched = false;
+
+	base = map->addr;
+	end = map->addr + (map->length - 1);
+
+	/* If the value is a legal u32, it will find a match. */
+	for (i = 0; i < P2A_REGION_COUNT; i++) {
+		const struct region *curr = &ctrl->config->regions[i];
+
+		/* If the top of this region is lower than your base, skip it.
+		 */
+		if (curr->max < base)
+			continue;
+
+		/* If the bottom of this region is higher than your end, bail.
+		 */
+		if (curr->min > end)
+			break;
+
+		/* Lock this and update it, therefore it someone else is
+		 * closing their file out, this'll preserve the increment.
+		 */
+		mutex_lock(&ctrl->tracking);
+		ctrl->readerwriters[i] += 1;
+		mutex_unlock(&ctrl->tracking);
+
+		/* Track with the user, so when they close their file, we can
+		 * decrement properly.
+		 */
+		priv->readwrite[i] += 1;
+
+		/* Enable the region as read-write. */
+		regmap_update_bits(ctrl->regmap, SCU2C, curr->bit, 0);
+		matched = true;
+	}
+
+	return matched;
+}
+
+static long aspeed_p2a_ioctl(struct file *file, unsigned int cmd,
+		unsigned long data)
+{
+	struct aspeed_p2a_user *priv = file->private_data;
+	struct aspeed_p2a_ctrl *ctrl = priv->parent;
+	void __user *arg = (void __user *)data;
+	struct aspeed_p2a_ctrl_mapping map;
+
+	if (copy_from_user(&map, arg, sizeof(map)))
+		return -EFAULT;
+
+	switch (cmd) {
+	case ASPEED_P2A_CTRL_IOCTL_SET_WINDOW:
+		/* If they want a region to be read-only, since the entire
+		 * region is read-only once enabled, we just need to track this
+		 * user wants to read from the bridge, and if it's not enabled.
+		 * Enable it.
+		 */
+		if (map.flags == ASPEED_P2A_CTRL_READ_ONLY) {
+			mutex_lock(&ctrl->tracking);
+			ctrl->readers += 1;
+			mutex_unlock(&ctrl->tracking);
+
+			/* Track with the user, so when they close their file,
+			 * we can decrement properly.
+			 */
+			priv->read += 1;
+		} else if (map.flags == ASPEED_P2A_CTRL_READWRITE) {
+			/* If we don't acquire any region return error. */
+			if (!aspeed_p2a_region_acquire(priv, ctrl, &map)) {
+				return -EINVAL;
+			}
+		} else {
+			/* Invalid map flags. */
+			return -EINVAL;
+		}
+
+		aspeed_p2a_enable_bridge(ctrl);
+		return 0;
+	case ASPEED_P2A_CTRL_IOCTL_GET_MEMORY_CONFIG:
+		/* This is a request for the memory-region and corresponding
+		 * length that is used by the driver for mmap.
+		 */
+
+		map.flags = 0;
+		map.addr = ctrl->mem_base;
+		map.length = ctrl->mem_size;
+
+		return copy_to_user(arg, &map, sizeof(map)) ? -EFAULT : 0;
+	}
+
+	return -EINVAL;
+}
+
+
+/*
+ * When a user opens this file, we create a structure to track their mappings.
+ *
+ * A user can map a region as read-only (bridge enabled), or read-write (bit
+ * flipped, and bridge enabled).  Either way, this tracking is used, s.t. when
+ * they release the device references are handled.
+ *
+ * The bridge is not enabled until a user calls an ioctl to map a region,
+ * simply opening the device does not enable it.
+ */
+static int aspeed_p2a_open(struct inode *inode, struct file *file)
+{
+	struct aspeed_p2a_user *priv;
+
+	priv = kmalloc(sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->file = file;
+	priv->read = 0;
+	memset(priv->readwrite, 0, sizeof(priv->readwrite));
+
+	/* The file's private_data is initialized to the p2a_ctrl. */
+	priv->parent = file->private_data;
+
+	/* Set the file's private_data to the user's data. */
+	file->private_data = priv;
+
+	return 0;
+}
+
+/*
+ * This will close the users mappings.  It will go through what they had opened
+ * for readwrite, and decrement those counts.  If at the end, this is the last
+ * user, it'll close the bridge.
+ */
+static int aspeed_p2a_release(struct inode *inode, struct file *file)
+{
+	int i;
+	u32 bits = 0;
+	bool open_regions = false;
+	struct aspeed_p2a_user *priv = file->private_data;
+
+	/* Lock others from changing these values until everything is updated
+	 * in one pass.
+	 */
+	mutex_lock(&priv->parent->tracking);
+
+	priv->parent->readers -= priv->read;
+
+	for (i = 0; i < P2A_REGION_COUNT; i++) {
+		priv->parent->readerwriters[i] -= priv->readwrite[i];
+
+		if (priv->parent->readerwriters[i] > 0)
+			open_regions = true;
+		else
+			bits |= priv->parent->config->regions[i].bit;
+	}
+
+	/* Setting a bit to 1 disables the region, so let's just OR with the
+	 * above to disable any.
+	 */
+
+	/* Note, if another user is trying to ioctl, they can't grab tracking,
+	 * and therefore can't grab either register mutex.
+	 * If another user is trying to close, they can't grab tracking either.
+	 */
+	regmap_update_bits(priv->parent->regmap, SCU2C, bits, bits);
+
+	/* If parent->readers is zero and open windows is 0, disable the
+	 * bridge.
+	 */
+	if (!open_regions && priv->parent->readers == 0)
+		aspeed_p2a_disable_bridge(priv->parent);
+
+	mutex_unlock(&priv->parent->tracking);
+
+	kfree(priv);
+
+	return 0;
+}
+
+static const struct file_operations aspeed_p2a_ctrl_fops = {
+	.owner = THIS_MODULE,
+	.mmap = aspeed_p2a_mmap,
+	.unlocked_ioctl = aspeed_p2a_ioctl,
+	.open = aspeed_p2a_open,
+	.release = aspeed_p2a_release,
+};
+
+/* The regions are controlled by SCU2C */
+static void aspeed_p2a_disable_all(struct aspeed_p2a_ctrl *p2a_ctrl)
+{
+	int i;
+	u32 value = 0;
+
+	for (i = 0; i < P2A_REGION_COUNT; i++)
+		value |= p2a_ctrl->config->regions[i].bit;
+
+	regmap_update_bits(p2a_ctrl->regmap, SCU2C, value, value);
+
+	/* Disable the bridge. */
+	aspeed_p2a_disable_bridge(p2a_ctrl);
+}
+
+static int aspeed_p2a_ctrl_probe(struct platform_device *pdev)
+{
+	struct aspeed_p2a_ctrl *misc_ctrl;
+	struct device *dev;
+	struct resource resm;
+	struct device_node *node;
+	int rc = 0;
+
+	dev = &pdev->dev;
+
+	misc_ctrl = devm_kzalloc(dev, sizeof(*misc_ctrl), GFP_KERNEL);
+	if (!misc_ctrl)
+		return -ENOMEM;
+
+	mutex_init(&misc_ctrl->tracking);
+
+	/* optional. */
+	node = of_parse_phandle(dev->of_node, "memory-region", 0);
+	if (node) {
+		rc = of_address_to_resource(node, 0, &resm);
+		of_node_put(node);
+		if (rc) {
+			dev_err(dev, "Couldn't address to resource for reserved memory\n");
+			return -ENODEV;
+		}
+
+		misc_ctrl->mem_size = resource_size(&resm);
+		misc_ctrl->mem_base = resm.start;
+	}
+
+	misc_ctrl->regmap = syscon_node_to_regmap(pdev->dev.parent->of_node);
+	if (IS_ERR(misc_ctrl->regmap)) {
+		dev_err(dev, "Couldn't get regmap\n");
+		return -ENODEV;
+	}
+
+	misc_ctrl->config = of_device_get_match_data(dev);
+
+	dev_set_drvdata(&pdev->dev, misc_ctrl);
+
+	aspeed_p2a_disable_all(misc_ctrl);
+
+	misc_ctrl->miscdev.minor = MISC_DYNAMIC_MINOR;
+	misc_ctrl->miscdev.name = DEVICE_NAME;
+	misc_ctrl->miscdev.fops = &aspeed_p2a_ctrl_fops;
+	misc_ctrl->miscdev.parent = dev;
+
+	rc = misc_register(&misc_ctrl->miscdev);
+	if (rc)
+		dev_err(dev, "Unable to register device\n");
+
+	return rc;
+}
+
+static int aspeed_p2a_ctrl_remove(struct platform_device *pdev)
+{
+	struct aspeed_p2a_ctrl *p2a_ctrl = dev_get_drvdata(&pdev->dev);
+
+	misc_deregister(&p2a_ctrl->miscdev);
+
+	return 0;
+}
+
+#define SCU2C_DRAM	BIT(25)
+#define SCU2C_SPI	BIT(24)
+#define SCU2C_SOC	BIT(23)
+#define SCU2C_FLASH	BIT(22)
+
+static const struct aspeed_p2a_model_data ast2400_model_data = {
+	.regions = {
+		{0x00000000, 0x17FFFFFF, SCU2C_FLASH},
+		{0x18000000, 0x1FFFFFFF, SCU2C_SOC},
+		{0x20000000, 0x2FFFFFFF, SCU2C_FLASH},
+		{0x30000000, 0x3FFFFFFF, SCU2C_SPI},
+		{0x40000000, 0x5FFFFFFF, SCU2C_DRAM},
+		{0x60000000, 0xFFFFFFFF, SCU2C_SOC},
+	}
+};
+
+static const struct aspeed_p2a_model_data ast2500_model_data = {
+	.regions = {
+		{0x00000000, 0x0FFFFFFF, SCU2C_FLASH},
+		{0x10000000, 0x1FFFFFFF, SCU2C_SOC},
+		{0x20000000, 0x3FFFFFFF, SCU2C_FLASH},
+		{0x40000000, 0x5FFFFFFF, SCU2C_SOC},
+		{0x60000000, 0x7FFFFFFF, SCU2C_SPI},
+		{0x80000000, 0xFFFFFFFF, SCU2C_DRAM},
+	}
+};
+
+static const struct of_device_id aspeed_p2a_ctrl_match[] = {
+	{ .compatible = "aspeed,ast2400-p2a-ctrl",
+	  .data = &ast2400_model_data },
+	{ .compatible = "aspeed,ast2500-p2a-ctrl",
+	  .data = &ast2500_model_data },
+	{ },
+};
+
+static struct platform_driver aspeed_p2a_ctrl_driver = {
+	.driver = {
+		.name		= DEVICE_NAME,
+		.of_match_table = aspeed_p2a_ctrl_match,
+	},
+	.probe = aspeed_p2a_ctrl_probe,
+	.remove = aspeed_p2a_ctrl_remove,
+};
+
+module_platform_driver(aspeed_p2a_ctrl_driver);
+
+MODULE_DEVICE_TABLE(of, aspeed_p2a_ctrl_match);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Patrick Venture <venture@google.com>");
+MODULE_DESCRIPTION("Control for aspeed 2400/2500 P2A VGA HOST to BMC mappings");