i2c-designware-amdpsp.c
// 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);
}