1 files changed, 425 insertions, 0 deletions
diff --git a/drivers/i2c/busses/i2c-designware-amdpsp.c b/drivers/i2c/busses/i2c-designware-amdpsp.c
new file mode 100644
index 000000000..8f36167bc
--- /dev/null
+++ b/drivers/i2c/busses/i2c-designware-amdpsp.c
@@ -0,0 +1,425 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bitfield.h>
+#include <linux/bits.h>
+#include <linux/i2c.h>
+#include <linux/io-64-nonatomic-lo-hi.h>
+#include <linux/psp-sev.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+
+#include <asm/msr.h>
+
+#include "i2c-designware-core.h"
+
+#define MSR_AMD_PSP_ADDR	0xc00110a2
+#define PSP_MBOX_OFFSET		0x10570
+#define PSP_CMD_TIMEOUT_US	(500 * USEC_PER_MSEC)
+
+#define PSP_I2C_RESERVATION_TIME_MS 100
+
+#define PSP_I2C_REQ_BUS_CMD		0x64
+#define PSP_I2C_REQ_RETRY_CNT		400
+#define PSP_I2C_REQ_RETRY_DELAY_US	(25 * USEC_PER_MSEC)
+#define PSP_I2C_REQ_STS_OK		0x0
+#define PSP_I2C_REQ_STS_BUS_BUSY	0x1
+#define PSP_I2C_REQ_STS_INV_PARAM	0x3
+
+#define PSP_MBOX_FIELDS_STS		GENMASK(15, 0)
+#define PSP_MBOX_FIELDS_CMD		GENMASK(23, 16)
+#define PSP_MBOX_FIELDS_RESERVED	GENMASK(29, 24)
+#define PSP_MBOX_FIELDS_RECOVERY	BIT(30)
+#define PSP_MBOX_FIELDS_READY		BIT(31)
+
+struct psp_req_buffer_hdr {
+	u32 total_size;
+	u32 status;
+};
+
+enum psp_i2c_req_type {
+	PSP_I2C_REQ_ACQUIRE,
+	PSP_I2C_REQ_RELEASE,
+	PSP_I2C_REQ_MAX
+};
+
+struct psp_i2c_req {
+	struct psp_req_buffer_hdr hdr;
+	enum psp_i2c_req_type type;
+};
+
+struct psp_mbox {
+	u32 cmd_fields;
+	u64 i2c_req_addr;
+} __packed;
+
+static DEFINE_MUTEX(psp_i2c_access_mutex);
+static unsigned long psp_i2c_sem_acquired;
+static void __iomem *mbox_iomem;
+static u32 psp_i2c_access_count;
+static bool psp_i2c_mbox_fail;
+static struct device *psp_i2c_dev;
+
+/*
+ * Implementation of PSP-x86 i2c-arbitration mailbox introduced for AMD Cezanne
+ * family of SoCs.
+ */
+
+static int psp_get_mbox_addr(unsigned long *mbox_addr)
+{
+	unsigned long long psp_mmio;
+
+	if (rdmsrl_safe(MSR_AMD_PSP_ADDR, &psp_mmio))
+		return -EIO;
+
+	*mbox_addr = (unsigned long)(psp_mmio + PSP_MBOX_OFFSET);
+
+	return 0;
+}
+
+static int psp_mbox_probe(void)
+{
+	unsigned long mbox_addr;
+	int ret;
+
+	ret = psp_get_mbox_addr(&mbox_addr);
+	if (ret)
+		return ret;
+
+	mbox_iomem = ioremap(mbox_addr, sizeof(struct psp_mbox));
+	if (!mbox_iomem)
+		return -ENOMEM;
+
+	return 0;
+}
+
+/* Recovery field should be equal 0 to start sending commands */
+static int psp_check_mbox_recovery(struct psp_mbox __iomem *mbox)
+{
+	u32 tmp;
+
+	tmp = readl(&mbox->cmd_fields);
+
+	return FIELD_GET(PSP_MBOX_FIELDS_RECOVERY, tmp);
+}
+
+static int psp_wait_cmd(struct psp_mbox __iomem *mbox)
+{
+	u32 tmp, expected;
+
+	/* Expect mbox_cmd to be cleared and ready bit to be set by PSP */
+	expected = FIELD_PREP(PSP_MBOX_FIELDS_READY, 1);
+
+	/*
+	 * Check for readiness of PSP mailbox in a tight loop in order to
+	 * process further as soon as command was consumed.
+	 */
+	return readl_poll_timeout(&mbox->cmd_fields, tmp, (tmp == expected),
+				  0, PSP_CMD_TIMEOUT_US);
+}
+
+/* Status equal to 0 means that PSP succeed processing command */
+static u32 psp_check_mbox_sts(struct psp_mbox __iomem *mbox)
+{
+	u32 cmd_reg;
+
+	cmd_reg = readl(&mbox->cmd_fields);
+
+	return FIELD_GET(PSP_MBOX_FIELDS_STS, cmd_reg);
+}
+
+static int psp_send_cmd(struct psp_i2c_req *req)
+{
+	struct psp_mbox __iomem *mbox = mbox_iomem;
+	phys_addr_t req_addr;
+	u32 cmd_reg;
+
+	if (psp_check_mbox_recovery(mbox))
+		return -EIO;
+
+	if (psp_wait_cmd(mbox))
+		return -EBUSY;
+
+	/*
+	 * Fill mailbox with address of command-response buffer, which will be
+	 * used for sending i2c requests as well as reading status returned by
+	 * PSP. Use physical address of buffer, since PSP will map this region.
+	 */
+	req_addr = __psp_pa((void *)req);
+	writeq(req_addr, &mbox->i2c_req_addr);
+
+	/* Write command register to trigger processing */
+	cmd_reg = FIELD_PREP(PSP_MBOX_FIELDS_CMD, PSP_I2C_REQ_BUS_CMD);
+	writel(cmd_reg, &mbox->cmd_fields);
+
+	if (psp_wait_cmd(mbox))
+		return -ETIMEDOUT;
+
+	if (psp_check_mbox_sts(mbox))
+		return -EIO;
+
+	return 0;
+}
+
+/* Helper to verify status returned by PSP */
+static int check_i2c_req_sts(struct psp_i2c_req *req)
+{
+	u32 status;
+
+	/* Status field in command-response buffer is updated by PSP */
+	status = READ_ONCE(req->hdr.status);
+
+	switch (status) {
+	case PSP_I2C_REQ_STS_OK:
+		return 0;
+	case PSP_I2C_REQ_STS_BUS_BUSY:
+		return -EBUSY;
+	case PSP_I2C_REQ_STS_INV_PARAM:
+	default:
+		return -EIO;
+	}
+}
+
+static int psp_send_check_i2c_req(struct psp_i2c_req *req)
+{
+	/*
+	 * Errors in x86-PSP i2c-arbitration protocol may occur at two levels:
+	 * 1. mailbox communication - PSP is not operational or some IO errors
+	 * with basic communication had happened;
+	 * 2. i2c-requests - PSP refuses to grant i2c arbitration to x86 for too
+	 * long.
+	 * In order to distinguish between these two in error handling code, all
+	 * errors on the first level (returned by psp_send_cmd) are shadowed by
+	 * -EIO.
+	 */
+	if (psp_send_cmd(req))
+		return -EIO;
+
+	return check_i2c_req_sts(req);
+}
+
+static int psp_send_i2c_req(enum psp_i2c_req_type i2c_req_type)
+{
+	struct psp_i2c_req *req;
+	unsigned long start;
+	int status, ret;
+
+	/* Allocate command-response buffer */
+	req = kzalloc(sizeof(*req), GFP_KERNEL);
+	if (!req)
+		return -ENOMEM;
+
+	req->hdr.total_size = sizeof(*req);
+	req->type = i2c_req_type;
+
+	start = jiffies;
+	ret = read_poll_timeout(psp_send_check_i2c_req, status,
+				(status != -EBUSY),
+				PSP_I2C_REQ_RETRY_DELAY_US,
+				PSP_I2C_REQ_RETRY_CNT * PSP_I2C_REQ_RETRY_DELAY_US,
+				0, req);
+	if (ret) {
+		dev_err(psp_i2c_dev, "Timed out waiting for PSP to %s I2C bus\n",
+			(i2c_req_type == PSP_I2C_REQ_ACQUIRE) ?
+			"release" : "acquire");
+		goto cleanup;
+	}
+
+	ret = status;
+	if (ret) {
+		dev_err(psp_i2c_dev, "PSP communication error\n");
+		goto cleanup;
+	}
+
+	dev_dbg(psp_i2c_dev, "Request accepted by PSP after %ums\n",
+		jiffies_to_msecs(jiffies - start));
+
+cleanup:
+	if (ret) {
+		dev_err(psp_i2c_dev, "Assume i2c bus is for exclusive host usage\n");
+		psp_i2c_mbox_fail = true;
+	}
+
+	kfree(req);
+	return ret;
+}
+
+static void release_bus(void)
+{
+	int status;
+
+	if (!psp_i2c_sem_acquired)
+		return;
+
+	status = psp_send_i2c_req(PSP_I2C_REQ_RELEASE);
+	if (status)
+		return;
+
+	dev_dbg(psp_i2c_dev, "PSP semaphore held for %ums\n",
+		jiffies_to_msecs(jiffies - psp_i2c_sem_acquired));
+
+	psp_i2c_sem_acquired = 0;
+}
+
+static void psp_release_i2c_bus_deferred(struct work_struct *work)
+{
+	mutex_lock(&psp_i2c_access_mutex);
+
+	/*
+	 * If there is any pending transaction, cannot release the bus here.
+	 * psp_release_i2c_bus will take care of this later.
+	 */
+	if (psp_i2c_access_count)
+		goto cleanup;
+
+	release_bus();
+
+cleanup:
+	mutex_unlock(&psp_i2c_access_mutex);
+}
+static DECLARE_DELAYED_WORK(release_queue, psp_release_i2c_bus_deferred);
+
+static int psp_acquire_i2c_bus(void)
+{
+	int status;
+
+	mutex_lock(&psp_i2c_access_mutex);
+
+	/* Return early if mailbox malfunctioned */
+	if (psp_i2c_mbox_fail)
+		goto cleanup;
+
+	psp_i2c_access_count++;
+
+	/*
+	 * No need to request bus arbitration once we are inside semaphore
+	 * reservation period.
+	 */
+	if (psp_i2c_sem_acquired)
+		goto cleanup;
+
+	status = psp_send_i2c_req(PSP_I2C_REQ_ACQUIRE);
+	if (status)
+		goto cleanup;
+
+	psp_i2c_sem_acquired = jiffies;
+
+	schedule_delayed_work(&release_queue,
+			      msecs_to_jiffies(PSP_I2C_RESERVATION_TIME_MS));
+
+	/*
+	 * In case of errors with PSP arbitrator psp_i2c_mbox_fail variable is
+	 * set above. As a consequence consecutive calls to acquire will bypass
+	 * communication with PSP. At any case i2c bus is granted to the caller,
+	 * thus always return success.
+	 */
+cleanup:
+	mutex_unlock(&psp_i2c_access_mutex);
+	return 0;
+}
+
+static void psp_release_i2c_bus(void)
+{
+	mutex_lock(&psp_i2c_access_mutex);
+
+	/* Return early if mailbox was malfunctional */
+	if (psp_i2c_mbox_fail)
+		goto cleanup;
+
+	/*
+	 * If we are last owner of PSP semaphore, need to release aribtration
+	 * via mailbox.
+	 */
+	psp_i2c_access_count--;
+	if (psp_i2c_access_count)
+		goto cleanup;
+
+	/*
+	 * Send a release command to PSP if the semaphore reservation timeout
+	 * elapsed but x86 still owns the controller.
+	 */
+	if (!delayed_work_pending(&release_queue))
+		release_bus();
+
+cleanup:
+	mutex_unlock(&psp_i2c_access_mutex);
+}
+
+/*
+ * Locking methods are based on the default implementation from
+ * drivers/i2c/i2c-core-base.c, but with psp acquire and release operations
+ * added. With this in place we can ensure that i2c clients on the bus shared
+ * with psp are able to lock HW access to the bus for arbitrary number of
+ * operations - that is e.g. write-wait-read.
+ */
+static void i2c_adapter_dw_psp_lock_bus(struct i2c_adapter *adapter,
+					unsigned int flags)
+{
+	psp_acquire_i2c_bus();
+	rt_mutex_lock_nested(&adapter->bus_lock, i2c_adapter_depth(adapter));
+}
+
+static int i2c_adapter_dw_psp_trylock_bus(struct i2c_adapter *adapter,
+					  unsigned int flags)
+{
+	int ret;
+
+	ret = rt_mutex_trylock(&adapter->bus_lock);
+	if (ret)
+		return ret;
+
+	psp_acquire_i2c_bus();
+
+	return ret;
+}
+
+static void i2c_adapter_dw_psp_unlock_bus(struct i2c_adapter *adapter,
+					  unsigned int flags)
+{
+	psp_release_i2c_bus();
+	rt_mutex_unlock(&adapter->bus_lock);
+}
+
+static const struct i2c_lock_operations i2c_dw_psp_lock_ops = {
+	.lock_bus = i2c_adapter_dw_psp_lock_bus,
+	.trylock_bus = i2c_adapter_dw_psp_trylock_bus,
+	.unlock_bus = i2c_adapter_dw_psp_unlock_bus,
+};
+
+int i2c_dw_amdpsp_probe_lock_support(struct dw_i2c_dev *dev)
+{
+	int ret;
+
+	if (!dev)
+		return -ENODEV;
+
+	if (!(dev->flags & ARBITRATION_SEMAPHORE))
+		return -ENODEV;
+
+	/* Allow to bind only one instance of a driver */
+	if (psp_i2c_dev)
+		return -EEXIST;
+
+	psp_i2c_dev = dev->dev;
+
+	ret = psp_mbox_probe();
+	if (ret)
+		return ret;
+
+	dev_info(psp_i2c_dev, "I2C bus managed by AMD PSP\n");
+
+	/*
+	 * Install global locking callbacks for adapter as well as internal i2c
+	 * controller locks.
+	 */
+	dev->adapter.lock_ops = &i2c_dw_psp_lock_ops;
+	dev->acquire_lock = psp_acquire_i2c_bus;
+	dev->release_lock = psp_release_i2c_bus;
+
+	return 0;
+}
+
+/* Unmap area used as a mailbox with PSP */
+void i2c_dw_amdpsp_remove_lock_support(struct dw_i2c_dev *dev)
+{
+	iounmap(mbox_iomem);
+}