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Subject[RFC PATCH 5/5] fsi/scom: Major overhaul
Date
This was too hard to split ... this adds a number of features
to the SCOM user interface:

- Support for indirect SCOMs

- read()/write() interface now handle errors and retries

- New ioctl() "raw" interface for use by debuggers

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
drivers/fsi/fsi-scom.c | 424 ++++++++++++++++++++++++++++++++++++---
include/uapi/linux/fsi.h | 56 ++++++
2 files changed, 450 insertions(+), 30 deletions(-)
create mode 100644 include/uapi/linux/fsi.h

diff --git a/drivers/fsi/fsi-scom.c b/drivers/fsi/fsi-scom.c
index e98573ecdae1..39c74351f1bf 100644
--- a/drivers/fsi/fsi-scom.c
+++ b/drivers/fsi/fsi-scom.c
@@ -24,6 +24,8 @@
#include <linux/list.h>
#include <linux/idr.h>

+#include <uapi/linux/fsi.h>
+
#define FSI_ENGID_SCOM 0x5

/* SCOM engine register set */
@@ -41,14 +43,36 @@
/* 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_ANY_ERR (SCOM_STATUS_ERR_SUMMARY | \
SCOM_STATUS_PROTECTION | \
+ SCOM_STATUS_PARITY | \
SCOM_STATUS_PIB_ABORT | \
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_RETRIES 100 /* Retries on busy */
+#define SCOM_MAX_IND_RETRIES 10 /* Retries indirect not ready */

struct scom_device {
struct list_head link;
@@ -56,7 +80,7 @@ struct scom_device {
struct miscdevice mdev;
struct mutex lock;
char name[32];
- int idx;
+ int idx;
};

#define to_scom_dev(x) container_of((x), struct scom_device, mdev)
@@ -65,80 +89,304 @@ static struct list_head scom_devices;

static DEFINE_IDA(scom_ida);

-static int put_scom(struct scom_device *scom_dev, uint64_t value,
- uint32_t addr)
+static int __put_scom(struct scom_device *scom_dev, uint64_t value,
+ uint32_t addr, uint32_t *status)
{
- __be32 data;
+ __be32 data, raw_status;
int rc;

- mutex_lock(&scom_dev->lock);
-
data = cpu_to_be32((value >> 32) & 0xffffffff);
rc = fsi_device_write(scom_dev->fsi_dev, SCOM_DATA0_REG, &data,
sizeof(uint32_t));
if (rc)
- goto bail;
+ 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)
- goto bail;
+ 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));
- bail:
- mutex_unlock(&scom_dev->lock);
- return rc;
+ 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)
+static int __get_scom(struct scom_device *scom_dev, uint64_t *value,
+ uint32_t addr, uint32_t *status)
{
- __be32 result, data;
+ __be32 data, raw_status;
int rc;


- mutex_lock(&scom_dev->lock);
*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)
- goto bail;
+ return rc;
+ rc = fsi_device_read(scom_dev->fsi_dev, SCOM_STATUS_REG, &raw_status,
+ sizeof(uint32_t));
+ if (rc)
+ return rc;

- rc = fsi_device_read(scom_dev->fsi_dev, SCOM_DATA0_REG, &result,
+ /*
+ * 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)
- goto bail;
-
- *value |= (uint64_t)be32_to_cpu(result) << 32;
- rc = fsi_device_read(scom_dev->fsi_dev, SCOM_DATA1_REG, &result,
+ 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)
- goto bail;
+ 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_PROTECTION)
+ return -EPERM;
+ if (status & SCOM_STATUS_PARITY) {
+ fsi_device_write(scom->fsi_dev, SCOM_FSI2PIB_RESET_REG, &dummy,
+ sizeof(uint32_t));
+ return -EIO;
+ }
+ /* Return -EBUSY on PIB abort to force a retry */
+ if (status & SCOM_STATUS_PIB_ABORT)
+ return -EBUSY;
+ if (status & SCOM_STATUS_ERR_SUMMARY) {
+ fsi_device_write(scom->fsi_dev, SCOM_FSI2PIB_RESET_REG, &dummy,
+ sizeof(uint32_t));
+ return -EIO;
+ }
+ 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;
+ }
+}

- *value |= be32_to_cpu(result);
- bail:
- mutex_unlock(&scom_dev->lock);
+static int put_scom(struct scom_device *scom, uint64_t value,
+ uint64_t addr)
+{
+ uint32_t status, dummy = -1;
+ int rc, retries;
+
+ for (retries = 0; retries < SCOM_MAX_RETRIES; retries++) {
+ rc = raw_put_scom(scom, value, addr, &status);
+ if (rc) {
+ /* Try resetting the bridge if FSI fails */
+ if (rc != -ENODEV && retries == 0) {
+ fsi_device_write(scom->fsi_dev, SCOM_FSI2PIB_RESET_REG,
+ &dummy, sizeof(uint32_t));
+ rc = -EBUSY;
+ } else
+ return rc;
+ } else
+ rc = handle_fsi2pib_status(scom, status);
+ if (rc && rc != -EBUSY)
+ break;
+ if (rc == 0) {
+ rc = handle_pib_status(scom,
+ (status & SCOM_STATUS_PIB_RESP_MASK)
+ >> SCOM_STATUS_PIB_RESP_SHIFT);
+ if (rc && rc != -EBUSY)
+ break;
+ }
+ if (rc == 0)
+ break;
+ msleep(1);
+ }
+ return rc;
+}
+
+static int get_scom(struct scom_device *scom, uint64_t *value,
+ uint64_t addr)
+{
+ uint32_t status, dummy = -1;
+ int rc, retries;
+
+ for (retries = 0; retries < SCOM_MAX_RETRIES; retries++) {
+ rc = raw_get_scom(scom, value, addr, &status);
+ if (rc) {
+ /* Try resetting the bridge if FSI fails */
+ if (rc != -ENODEV && retries == 0) {
+ fsi_device_write(scom->fsi_dev, SCOM_FSI2PIB_RESET_REG,
+ &dummy, sizeof(uint32_t));
+ rc = -EBUSY;
+ } else
+ return rc;
+ } else
+ rc = handle_fsi2pib_status(scom, status);
+ if (rc && rc != -EBUSY)
+ break;
+ if (rc == 0) {
+ rc = handle_pib_status(scom,
+ (status & SCOM_STATUS_PIB_RESP_MASK)
+ >> SCOM_STATUS_PIB_RESP_SHIFT);
+ if (rc && rc != -EBUSY)
+ break;
+ }
+ if (rc == 0)
+ break;
+ msleep(1);
+ }
return rc;
}

static ssize_t scom_read(struct file *filep, char __user *buf, size_t len,
loff_t *offset)
{
- int rc;
struct miscdevice *mdev =
(struct miscdevice *)filep->private_data;
struct scom_device *scom = to_scom_dev(mdev);
struct device *dev = &scom->fsi_dev->dev;
uint64_t val;
+ int rc;

if (len != sizeof(uint64_t))
return -EINVAL;

+ mutex_lock(&scom->lock);
rc = get_scom(scom, &val, *offset);
+ mutex_unlock(&scom->lock);
if (rc) {
dev_dbg(dev, "get_scom fail:%d\n", rc);
return rc;
@@ -169,7 +417,9 @@ static ssize_t scom_write(struct file *filep, const char __user *buf,
return -EINVAL;
}

+ mutex_lock(&scom->lock);
rc = put_scom(scom, val, *offset);
+ mutex_unlock(&scom->lock);
if (rc) {
dev_dbg(dev, "put_scom failed with:%d\n", rc);
return rc;
@@ -193,11 +443,125 @@ static loff_t scom_llseek(struct file *file, loff_t offset, int whence)
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 miscdevice *mdev = file->private_data;
+ struct scom_device *scom = to_scom_dev(mdev);
+ void __user *argp = (void __user *)arg;
+ int rc = -ENOTTY;
+
+ mutex_lock(&scom->lock);
+ 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 const struct file_operations scom_fops = {
- .owner = THIS_MODULE,
- .llseek = scom_llseek,
- .read = scom_read,
- .write = scom_write,
+ .owner = THIS_MODULE,
+ .llseek = scom_llseek,
+ .read = scom_read,
+ .write = scom_write,
+ .unlocked_ioctl = scom_ioctl,
};

static int scom_probe(struct device *dev)
diff --git a/include/uapi/linux/fsi.h b/include/uapi/linux/fsi.h
new file mode 100644
index 000000000000..6008d93f2e48
--- /dev/null
+++ b/include/uapi/linux/fsi.h
@@ -0,0 +1,56 @@
+#ifndef _UAPI_LINUX_FSI_H
+#define _UAPI_LINUX_FSI_H
+
+#include <linux/ioctl.h>
+
+/*
+ * /dev/scom "raw" ioctl interface
+ *
+ * The driver supports a high level "read/write" interface which
+ * handles retries and converts the status to Linux error codes,
+ * however low level tools an debugger need to access the "raw"
+ * HW status information and interpret it themselves, so this
+ * ioctl interface is also provided for their use case.
+ */
+
+/* Structure for SCOM read/write */
+struct scom_access {
+ __u64 addr; /* SCOM address, supports indirect */
+ __u64 data; /* SCOM data (in for write, out for read) */
+ __u64 mask; /* Data mask for writes */
+ __u32 intf_errors; /* Interface error flags */
+#define SCOM_INTF_ERR_PARITY 0x00000001 /* Parity error */
+#define SCOM_INTF_ERR_PROTECTION 0x00000002 /* Blocked by secure boot */
+#define SCOM_INTF_ERR_ABORT 0x00000004 /* PIB reset during access */
+#define SCOM_INTF_ERR_UNKNOWN 0x80000000 /* Unknown error */
+ /*
+ * Note: Any other bit set in intf_errors need to be considered as an
+ * error. Future implementations may define new error conditions. The
+ * pib_status below is only valid if intf_errors is 0.
+ */
+ __u8 pib_status; /* 3-bit PIB status */
+#define SCOM_PIB_SUCCESS 0 /* Access successful */
+#define SCOM_PIB_BLOCKED 1 /* PIB blocked, pls retry */
+#define SCOM_PIB_OFFLINE 2 /* Chiplet offline */
+#define SCOM_PIB_PARTIAL 3 /* Partial good */
+#define SCOM_PIB_BAD_ADDR 4 /* Invalid address */
+#define SCOM_PIB_CLK_ERR 5 /* Clock error */
+#define SCOM_PIB_PARITY_ERR 6 /* Parity error on the PIB bus */
+#define SCOM_PIB_TIMEOUT 7 /* Bus timeout */
+ __u8 pad;
+};
+
+/* Flags for SCOM check */
+#define SCOM_CHECK_SUPPORTED 0x00000001 /* Interface supported */
+#define SCOM_CHECK_PROTECTED 0x00000002 /* Interface blocked by secure boot */
+
+/* Flags for SCOM reset */
+#define SCOM_RESET_INTF 0x00000001 /* Reset interface */
+#define SCOM_RESET_PIB 0x00000002 /* Reset PIB */
+
+#define FSI_SCOM_CHECK _IOR('s', 0x00, __u32)
+#define FSI_SCOM_READ _IOWR('s', 0x01, struct scom_access)
+#define FSI_SCOM_WRITE _IOWR('s', 0x02, struct scom_access)
+#define FSI_SCOM_RESET _IOW('s', 0x03, __u32)
+
+#endif /* _UAPI_LINUX_FSI_H */
--
2.17.0
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