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Subject[RFC PATCH 1/5] fsi/scom: Add mutex around FSI2PIB accesses
Date
Otherwise, multiple clients can open the driver and attempt
to access the PIB at the same time, thus clobbering each other
in the process.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
drivers/fsi/fsi-scom.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/drivers/fsi/fsi-scom.c b/drivers/fsi/fsi-scom.c
index c8eb5e5b94a7..3cba0eb645e1 100644
--- a/drivers/fsi/fsi-scom.c
+++ b/drivers/fsi/fsi-scom.c
@@ -37,6 +37,7 @@ struct scom_device {
struct list_head link;
struct fsi_device *fsi_dev;
struct miscdevice mdev;
+ struct mutex lock;
char name[32];
int idx;
};
@@ -53,21 +54,26 @@ static int put_scom(struct scom_device *scom_dev, uint64_t value,
int rc;
uint32_t data;

+ 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)
- return rc;
+ goto bail;

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;
+ goto bail;

data = cpu_to_be32(SCOM_WRITE_CMD | addr);
- return fsi_device_write(scom_dev->fsi_dev, SCOM_CMD_REG, &data,
+ rc = fsi_device_write(scom_dev->fsi_dev, SCOM_CMD_REG, &data,
sizeof(uint32_t));
+ bail:
+ mutex_unlock(&scom_dev->lock);
+ return rc;
}

static int get_scom(struct scom_device *scom_dev, uint64_t *value,
@@ -76,27 +82,31 @@ static int get_scom(struct scom_device *scom_dev, uint64_t *value,
uint32_t result, data;
int rc;

+
+ mutex_lock(&scom_dev->lock);
*value = 0ULL;
data = cpu_to_be32(addr);
rc = fsi_device_write(scom_dev->fsi_dev, SCOM_CMD_REG, &data,
sizeof(uint32_t));
if (rc)
- return rc;
+ goto bail;

rc = fsi_device_read(scom_dev->fsi_dev, SCOM_DATA0_REG, &result,
sizeof(uint32_t));
if (rc)
- return rc;
+ goto bail;

*value |= (uint64_t)cpu_to_be32(result) << 32;
rc = fsi_device_read(scom_dev->fsi_dev, SCOM_DATA1_REG, &result,
sizeof(uint32_t));
if (rc)
- return rc;
+ goto bail;

*value |= cpu_to_be32(result);

- return 0;
+ bail:
+ mutex_unlock(&scom_dev->lock);
+ return rc;
}

static ssize_t scom_read(struct file *filep, char __user *buf, size_t len,
@@ -183,6 +193,7 @@ static int scom_probe(struct device *dev)
if (!scom)
return -ENOMEM;

+ mutex_init(&scom->lock);
scom->idx = ida_simple_get(&scom_ida, 1, INT_MAX, GFP_KERNEL);
snprintf(scom->name, sizeof(scom->name), "scom%d", scom->idx);
scom->fsi_dev = fsi_dev;
--
2.17.0
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