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linux/drivers/fsi/fsi-scom.c
Joel Stanley f72ddbe1d7 fsi: scom: Remove retries 
On a functioning FSI link there is not need to retry a write when doing
a scom in the driver.

Allow the higher layers (eg. userspace) to attempt a retry if they want,
or to accept that the address they are talking to is not accessible.

By removing the retries we can separate the error handling from retry
logic. In particular -EBUSY was used to force the get/put scom logic to
retry.

Signed-off-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20210527070109.225198-1-joel@jms.id.au
Signed-off-by: Joel Stanley <joel@jms.id.au>
2021-06-04 14:24:02 +09:30

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// SPDX-License-Identifier: GPL-2.0-only
/*
* SCOM FSI Client device driver
*
* Copyright (C) IBM Corporation 2016
*/
#include <linux/fsi.h>
#include <linux/module.h>
#include <linux/cdev.h>
#include <linux/delay.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <uapi/linux/fsi.h>
#define FSI_ENGID_SCOM 0x5
/* SCOM engine register set */
#define SCOM_DATA0_REG 0x00
#define SCOM_DATA1_REG 0x04
#define SCOM_CMD_REG 0x08
#define SCOM_FSI2PIB_RESET_REG 0x18
#define SCOM_STATUS_REG 0x1C /* Read */
#define SCOM_PIB_RESET_REG 0x1C /* Write */
/* Command register */
#define SCOM_WRITE_CMD 0x80000000
#define SCOM_READ_CMD 0x00000000
/* Status register bits */
#define SCOM_STATUS_ERR_SUMMARY 0x80000000
#define SCOM_STATUS_PROTECTION 0x01000000
#define SCOM_STATUS_PARITY 0x04000000
#define SCOM_STATUS_PIB_ABORT 0x00100000
#define SCOM_STATUS_PIB_RESP_MASK 0x00007000
#define SCOM_STATUS_PIB_RESP_SHIFT 12
#define SCOM_STATUS_FSI2PIB_ERROR (SCOM_STATUS_PROTECTION | \
SCOM_STATUS_PARITY | \
SCOM_STATUS_PIB_ABORT)
#define SCOM_STATUS_ANY_ERR (SCOM_STATUS_FSI2PIB_ERROR | \
SCOM_STATUS_PIB_RESP_MASK)
/* SCOM address encodings */
#define XSCOM_ADDR_IND_FLAG BIT_ULL(63)
#define XSCOM_ADDR_INF_FORM1 BIT_ULL(60)
/* SCOM indirect stuff */
#define XSCOM_ADDR_DIRECT_PART 0x7fffffffull
#define XSCOM_ADDR_INDIRECT_PART 0x000fffff00000000ull
#define XSCOM_DATA_IND_READ BIT_ULL(63)
#define XSCOM_DATA_IND_COMPLETE BIT_ULL(31)
#define XSCOM_DATA_IND_ERR_MASK 0x70000000ull
#define XSCOM_DATA_IND_ERR_SHIFT 28
#define XSCOM_DATA_IND_DATA 0x0000ffffull
#define XSCOM_DATA_IND_FORM1_DATA 0x000fffffffffffffull
#define XSCOM_ADDR_FORM1_LOW 0x000ffffffffull
#define XSCOM_ADDR_FORM1_HI 0xfff00000000ull
#define XSCOM_ADDR_FORM1_HI_SHIFT 20
/* Retries */
#define SCOM_MAX_IND_RETRIES 10 /* Retries indirect not ready */
struct scom_device {
struct list_head link;
struct fsi_device *fsi_dev;
struct device dev;
struct cdev cdev;
struct mutex lock;
bool dead;
};
static int __put_scom(struct scom_device *scom_dev, uint64_t value,
uint32_t addr, uint32_t *status)
{
__be32 data, raw_status;
int rc;
data = cpu_to_be32((value >> 32) & 0xffffffff);
rc = fsi_device_write(scom_dev->fsi_dev, SCOM_DATA0_REG, &data,
sizeof(uint32_t));
if (rc)
return rc;
data = cpu_to_be32(value & 0xffffffff);
rc = fsi_device_write(scom_dev->fsi_dev, SCOM_DATA1_REG, &data,
sizeof(uint32_t));
if (rc)
return rc;
data = cpu_to_be32(SCOM_WRITE_CMD | addr);
rc = fsi_device_write(scom_dev->fsi_dev, SCOM_CMD_REG, &data,
sizeof(uint32_t));
if (rc)
return rc;
rc = fsi_device_read(scom_dev->fsi_dev, SCOM_STATUS_REG, &raw_status,
sizeof(uint32_t));
if (rc)
return rc;
*status = be32_to_cpu(raw_status);
return 0;
}
static int __get_scom(struct scom_device *scom_dev, uint64_t *value,
uint32_t addr, uint32_t *status)
{
__be32 data, raw_status;
int rc;
*value = 0ULL;
data = cpu_to_be32(SCOM_READ_CMD | addr);
rc = fsi_device_write(scom_dev->fsi_dev, SCOM_CMD_REG, &data,
sizeof(uint32_t));
if (rc)
return rc;
rc = fsi_device_read(scom_dev->fsi_dev, SCOM_STATUS_REG, &raw_status,
sizeof(uint32_t));
if (rc)
return rc;
/*
* Read the data registers even on error, so we don't have
* to interpret the status register here.
*/
rc = fsi_device_read(scom_dev->fsi_dev, SCOM_DATA0_REG, &data,
sizeof(uint32_t));
if (rc)
return rc;
*value |= (uint64_t)be32_to_cpu(data) << 32;
rc = fsi_device_read(scom_dev->fsi_dev, SCOM_DATA1_REG, &data,
sizeof(uint32_t));
if (rc)
return rc;
*value |= be32_to_cpu(data);
*status = be32_to_cpu(raw_status);
return rc;
}
static int put_indirect_scom_form0(struct scom_device *scom, uint64_t value,
uint64_t addr, uint32_t *status)
{
uint64_t ind_data, ind_addr;
int rc, retries, err = 0;
if (value & ~XSCOM_DATA_IND_DATA)
return -EINVAL;
ind_addr = addr & XSCOM_ADDR_DIRECT_PART;
ind_data = (addr & XSCOM_ADDR_INDIRECT_PART) | value;
rc = __put_scom(scom, ind_data, ind_addr, status);
if (rc || (*status & SCOM_STATUS_ANY_ERR))
return rc;
for (retries = 0; retries < SCOM_MAX_IND_RETRIES; retries++) {
rc = __get_scom(scom, &ind_data, addr, status);
if (rc || (*status & SCOM_STATUS_ANY_ERR))
return rc;
err = (ind_data & XSCOM_DATA_IND_ERR_MASK) >> XSCOM_DATA_IND_ERR_SHIFT;
*status = err << SCOM_STATUS_PIB_RESP_SHIFT;
if ((ind_data & XSCOM_DATA_IND_COMPLETE) || (err != SCOM_PIB_BLOCKED))
return 0;
msleep(1);
}
return rc;
}
static int put_indirect_scom_form1(struct scom_device *scom, uint64_t value,
uint64_t addr, uint32_t *status)
{
uint64_t ind_data, ind_addr;
if (value & ~XSCOM_DATA_IND_FORM1_DATA)
return -EINVAL;
ind_addr = addr & XSCOM_ADDR_FORM1_LOW;
ind_data = value | (addr & XSCOM_ADDR_FORM1_HI) << XSCOM_ADDR_FORM1_HI_SHIFT;
return __put_scom(scom, ind_data, ind_addr, status);
}
static int get_indirect_scom_form0(struct scom_device *scom, uint64_t *value,
uint64_t addr, uint32_t *status)
{
uint64_t ind_data, ind_addr;
int rc, retries, err = 0;
ind_addr = addr & XSCOM_ADDR_DIRECT_PART;
ind_data = (addr & XSCOM_ADDR_INDIRECT_PART) | XSCOM_DATA_IND_READ;
rc = __put_scom(scom, ind_data, ind_addr, status);
if (rc || (*status & SCOM_STATUS_ANY_ERR))
return rc;
for (retries = 0; retries < SCOM_MAX_IND_RETRIES; retries++) {
rc = __get_scom(scom, &ind_data, addr, status);
if (rc || (*status & SCOM_STATUS_ANY_ERR))
return rc;
err = (ind_data & XSCOM_DATA_IND_ERR_MASK) >> XSCOM_DATA_IND_ERR_SHIFT;
*status = err << SCOM_STATUS_PIB_RESP_SHIFT;
*value = ind_data & XSCOM_DATA_IND_DATA;
if ((ind_data & XSCOM_DATA_IND_COMPLETE) || (err != SCOM_PIB_BLOCKED))
return 0;
msleep(1);
}
return rc;
}
static int raw_put_scom(struct scom_device *scom, uint64_t value,
uint64_t addr, uint32_t *status)
{
if (addr & XSCOM_ADDR_IND_FLAG) {
if (addr & XSCOM_ADDR_INF_FORM1)
return put_indirect_scom_form1(scom, value, addr, status);
else
return put_indirect_scom_form0(scom, value, addr, status);
} else
return __put_scom(scom, value, addr, status);
}
static int raw_get_scom(struct scom_device *scom, uint64_t *value,
uint64_t addr, uint32_t *status)
{
if (addr & XSCOM_ADDR_IND_FLAG) {
if (addr & XSCOM_ADDR_INF_FORM1)
return -ENXIO;
return get_indirect_scom_form0(scom, value, addr, status);
} else
return __get_scom(scom, value, addr, status);
}
static int handle_fsi2pib_status(struct scom_device *scom, uint32_t status)
{
uint32_t dummy = -1;
if (status & SCOM_STATUS_FSI2PIB_ERROR)
fsi_device_write(scom->fsi_dev, SCOM_FSI2PIB_RESET_REG, &dummy,
sizeof(uint32_t));
if (status & SCOM_STATUS_PROTECTION)
return -EPERM;
if (status & SCOM_STATUS_PARITY)
return -EIO;
if (status & SCOM_STATUS_PIB_ABORT)
return -EBUSY;
return 0;
}
static int handle_pib_status(struct scom_device *scom, uint8_t status)
{
uint32_t dummy = -1;
if (status == SCOM_PIB_SUCCESS)
return 0;
if (status == SCOM_PIB_BLOCKED)
return -EBUSY;
/* Reset the bridge */
fsi_device_write(scom->fsi_dev, SCOM_FSI2PIB_RESET_REG, &dummy,
sizeof(uint32_t));
switch(status) {
case SCOM_PIB_OFFLINE:
return -ENODEV;
case SCOM_PIB_BAD_ADDR:
return -ENXIO;
case SCOM_PIB_TIMEOUT:
return -ETIMEDOUT;
case SCOM_PIB_PARTIAL:
case SCOM_PIB_CLK_ERR:
case SCOM_PIB_PARITY_ERR:
default:
return -EIO;
}
}
static int put_scom(struct scom_device *scom, uint64_t value,
uint64_t addr)
{
uint32_t status;
int rc;
rc = raw_put_scom(scom, value, addr, &status);
if (rc == -ENODEV)
return rc;
rc = handle_fsi2pib_status(scom, status);
if (rc)
return rc;
return handle_pib_status(scom,
(status & SCOM_STATUS_PIB_RESP_MASK)
>> SCOM_STATUS_PIB_RESP_SHIFT);
}
static int get_scom(struct scom_device *scom, uint64_t *value,
uint64_t addr)
{
uint32_t status;
int rc;
rc = raw_get_scom(scom, value, addr, &status);
if (rc == -ENODEV)
return rc;
rc = handle_fsi2pib_status(scom, status);
if (rc)
return rc;
return handle_pib_status(scom,
(status & SCOM_STATUS_PIB_RESP_MASK)
>> SCOM_STATUS_PIB_RESP_SHIFT);
}
static ssize_t scom_read(struct file *filep, char __user *buf, size_t len,
loff_t *offset)
{
struct scom_device *scom = filep->private_data;
struct device *dev = &scom->fsi_dev->dev;
uint64_t val;
int rc;
if (len != sizeof(uint64_t))
return -EINVAL;
mutex_lock(&scom->lock);
if (scom->dead)
rc = -ENODEV;
else
rc = get_scom(scom, &val, *offset);
mutex_unlock(&scom->lock);
if (rc) {
dev_dbg(dev, "get_scom fail:%d\n", rc);
return rc;
}
rc = copy_to_user(buf, &val, len);
if (rc)
dev_dbg(dev, "copy to user failed:%d\n", rc);
return rc ? rc : len;
}
static ssize_t scom_write(struct file *filep, const char __user *buf,
size_t len, loff_t *offset)
{
int rc;
struct scom_device *scom = filep->private_data;
struct device *dev = &scom->fsi_dev->dev;
uint64_t val;
if (len != sizeof(uint64_t))
return -EINVAL;
rc = copy_from_user(&val, buf, len);
if (rc) {
dev_dbg(dev, "copy from user failed:%d\n", rc);
return -EINVAL;
}
mutex_lock(&scom->lock);
if (scom->dead)
rc = -ENODEV;
else
rc = put_scom(scom, val, *offset);
mutex_unlock(&scom->lock);
if (rc) {
dev_dbg(dev, "put_scom failed with:%d\n", rc);
return rc;
}
return len;
}
static loff_t scom_llseek(struct file *file, loff_t offset, int whence)
{
switch (whence) {
case SEEK_CUR:
break;
case SEEK_SET:
file->f_pos = offset;
break;
default:
return -EINVAL;
}
return offset;
}
static void raw_convert_status(struct scom_access *acc, uint32_t status)
{
acc->pib_status = (status & SCOM_STATUS_PIB_RESP_MASK) >>
SCOM_STATUS_PIB_RESP_SHIFT;
acc->intf_errors = 0;
if (status & SCOM_STATUS_PROTECTION)
acc->intf_errors |= SCOM_INTF_ERR_PROTECTION;
else if (status & SCOM_STATUS_PARITY)
acc->intf_errors |= SCOM_INTF_ERR_PARITY;
else if (status & SCOM_STATUS_PIB_ABORT)
acc->intf_errors |= SCOM_INTF_ERR_ABORT;
else if (status & SCOM_STATUS_ERR_SUMMARY)
acc->intf_errors |= SCOM_INTF_ERR_UNKNOWN;
}
static int scom_raw_read(struct scom_device *scom, void __user *argp)
{
struct scom_access acc;
uint32_t status;
int rc;
if (copy_from_user(&acc, argp, sizeof(struct scom_access)))
return -EFAULT;
rc = raw_get_scom(scom, &acc.data, acc.addr, &status);
if (rc)
return rc;
raw_convert_status(&acc, status);
if (copy_to_user(argp, &acc, sizeof(struct scom_access)))
return -EFAULT;
return 0;
}
static int scom_raw_write(struct scom_device *scom, void __user *argp)
{
u64 prev_data, mask, data;
struct scom_access acc;
uint32_t status;
int rc;
if (copy_from_user(&acc, argp, sizeof(struct scom_access)))
return -EFAULT;
if (acc.mask) {
rc = raw_get_scom(scom, &prev_data, acc.addr, &status);
if (rc)
return rc;
if (status & SCOM_STATUS_ANY_ERR)
goto fail;
mask = acc.mask;
} else {
prev_data = mask = -1ull;
}
data = (prev_data & ~mask) | (acc.data & mask);
rc = raw_put_scom(scom, data, acc.addr, &status);
if (rc)
return rc;
fail:
raw_convert_status(&acc, status);
if (copy_to_user(argp, &acc, sizeof(struct scom_access)))
return -EFAULT;
return 0;
}
static int scom_reset(struct scom_device *scom, void __user *argp)
{
uint32_t flags, dummy = -1;
int rc = 0;
if (get_user(flags, (__u32 __user *)argp))
return -EFAULT;
if (flags & SCOM_RESET_PIB)
rc = fsi_device_write(scom->fsi_dev, SCOM_PIB_RESET_REG, &dummy,
sizeof(uint32_t));
if (!rc && (flags & (SCOM_RESET_PIB | SCOM_RESET_INTF)))
rc = fsi_device_write(scom->fsi_dev, SCOM_FSI2PIB_RESET_REG, &dummy,
sizeof(uint32_t));
return rc;
}
static int scom_check(struct scom_device *scom, void __user *argp)
{
/* Still need to find out how to get "protected" */
return put_user(SCOM_CHECK_SUPPORTED, (__u32 __user *)argp);
}
static long scom_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
struct scom_device *scom = file->private_data;
void __user *argp = (void __user *)arg;
int rc = -ENOTTY;
mutex_lock(&scom->lock);
if (scom->dead) {
mutex_unlock(&scom->lock);
return -ENODEV;
}
switch(cmd) {
case FSI_SCOM_CHECK:
rc = scom_check(scom, argp);
break;
case FSI_SCOM_READ:
rc = scom_raw_read(scom, argp);
break;
case FSI_SCOM_WRITE:
rc = scom_raw_write(scom, argp);
break;
case FSI_SCOM_RESET:
rc = scom_reset(scom, argp);
break;
}
mutex_unlock(&scom->lock);
return rc;
}
static int scom_open(struct inode *inode, struct file *file)
{
struct scom_device *scom = container_of(inode->i_cdev, struct scom_device, cdev);
file->private_data = scom;
return 0;
}
static const struct file_operations scom_fops = {
.owner = THIS_MODULE,
.open = scom_open,
.llseek = scom_llseek,
.read = scom_read,
.write = scom_write,
.unlocked_ioctl = scom_ioctl,
};
static void scom_free(struct device *dev)
{
struct scom_device *scom = container_of(dev, struct scom_device, dev);
put_device(&scom->fsi_dev->dev);
kfree(scom);
}
static int scom_probe(struct device *dev)
{
struct fsi_device *fsi_dev = to_fsi_dev(dev);
struct scom_device *scom;
int rc, didx;
scom = kzalloc(sizeof(*scom), GFP_KERNEL);
if (!scom)
return -ENOMEM;
dev_set_drvdata(dev, scom);
mutex_init(&scom->lock);
/* Grab a reference to the device (parent of our cdev), we'll drop it later */
if (!get_device(dev)) {
kfree(scom);
return -ENODEV;
}
scom->fsi_dev = fsi_dev;
/* Create chardev for userspace access */
scom->dev.type = &fsi_cdev_type;
scom->dev.parent = dev;
scom->dev.release = scom_free;
device_initialize(&scom->dev);
/* Allocate a minor in the FSI space */
rc = fsi_get_new_minor(fsi_dev, fsi_dev_scom, &scom->dev.devt, &didx);
if (rc)
goto err;
dev_set_name(&scom->dev, "scom%d", didx);
cdev_init(&scom->cdev, &scom_fops);
rc = cdev_device_add(&scom->cdev, &scom->dev);
if (rc) {
dev_err(dev, "Error %d creating char device %s\n",
rc, dev_name(&scom->dev));
goto err_free_minor;
}
return 0;
err_free_minor:
fsi_free_minor(scom->dev.devt);
err:
put_device(&scom->dev);
return rc;
}
static int scom_remove(struct device *dev)
{
struct scom_device *scom = dev_get_drvdata(dev);
mutex_lock(&scom->lock);
scom->dead = true;
mutex_unlock(&scom->lock);
cdev_device_del(&scom->cdev, &scom->dev);
fsi_free_minor(scom->dev.devt);
put_device(&scom->dev);
return 0;
}
static const struct fsi_device_id scom_ids[] = {
{
.engine_type = FSI_ENGID_SCOM,
.version = FSI_VERSION_ANY,
},
{ 0 }
};
static struct fsi_driver scom_drv = {
.id_table = scom_ids,
.drv = {
.name = "scom",
.bus = &fsi_bus_type,
.probe = scom_probe,
.remove = scom_remove,
}
};
static int scom_init(void)
{
return fsi_driver_register(&scom_drv);
}
static void scom_exit(void)
{
fsi_driver_unregister(&scom_drv);
}
module_init(scom_init);
module_exit(scom_exit);
MODULE_LICENSE("GPL");
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