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i2c: wmt: fix a bug when thread blocked
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During each byte access, the host performs clock stretching.

To reduce the host performs clock stretching, move most of
the per-msg processing to the interrupt context.

Suggested-by: Wolfram Sang <[email protected]>
Reviewed-by: Wolfram Sang <[email protected]>
Signed-off-by: Hans Hu <[email protected]>
Signed-off-by: Andi Shyti <[email protected]>
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Hans Hu authored and Andi Shyti committed May 5, 2024
1 parent 013fa16 commit 2e829cc
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Showing 2 changed files with 80 additions and 71 deletions.
145 changes: 76 additions & 69 deletions drivers/i2c/busses/i2c-viai2c-common.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -18,37 +18,18 @@ int viai2c_wait_bus_not_busy(struct viai2c *i2c)
return 0;
}

int viai2c_check_status(struct viai2c *i2c)
{
int ret = 0;
unsigned long time_left;

time_left = wait_for_completion_timeout(&i2c->complete,
msecs_to_jiffies(500));
if (!time_left)
return -ETIMEDOUT;

if (i2c->cmd_status & VIAI2C_ISR_NACK_ADDR)
ret = -EIO;

if (i2c->cmd_status & VIAI2C_ISR_SCL_TIMEOUT)
ret = -ETIMEDOUT;

return ret;
}

static int viai2c_write(struct viai2c *i2c, struct i2c_msg *pmsg, int last)
{
u16 val, tcr_val = i2c->tcr;
int ret;
int xfer_len = 0;

i2c->last = last;

if (pmsg->len == 0) {
/*
* We still need to run through the while (..) once, so
* start at -1 and break out early from the loop
*/
xfer_len = -1;
i2c->xfered_len = -1;
writew(0, i2c->base + VIAI2C_REG_CDR);
} else {
writew(pmsg->buf[0] & 0xFF, i2c->base + VIAI2C_REG_CDR);
Expand All @@ -73,42 +54,15 @@ static int viai2c_write(struct viai2c *i2c, struct i2c_msg *pmsg, int last)
writew(val, i2c->base + VIAI2C_REG_CR);
}

while (xfer_len < pmsg->len) {
ret = viai2c_check_status(i2c);
if (ret)
return ret;

xfer_len++;

val = readw(i2c->base + VIAI2C_REG_CSR);
if (val & VIAI2C_CSR_RCV_NOT_ACK) {
dev_dbg(i2c->dev, "write RCV NACK error\n");
return -EIO;
}

if (pmsg->len == 0) {
val = VIAI2C_CR_TX_END | VIAI2C_CR_CPU_RDY | VIAI2C_CR_ENABLE;
writew(val, i2c->base + VIAI2C_REG_CR);
break;
}

if (xfer_len == pmsg->len) {
if (last != 1)
writew(VIAI2C_CR_ENABLE, i2c->base + VIAI2C_REG_CR);
} else {
writew(pmsg->buf[xfer_len] & 0xFF, i2c->base + VIAI2C_REG_CDR);
writew(VIAI2C_CR_CPU_RDY | VIAI2C_CR_ENABLE, i2c->base + VIAI2C_REG_CR);
}
}
if (!wait_for_completion_timeout(&i2c->complete, VIAI2C_TIMEOUT))
return -ETIMEDOUT;

return 0;
return i2c->ret;
}

static int viai2c_read(struct viai2c *i2c, struct i2c_msg *pmsg)
{
u16 val, tcr_val = i2c->tcr;
int ret;
u32 xfer_len = 0;

val = readw(i2c->base + VIAI2C_REG_CR);
val &= ~(VIAI2C_CR_TX_END | VIAI2C_CR_RX_END);
Expand All @@ -133,21 +87,10 @@ static int viai2c_read(struct viai2c *i2c, struct i2c_msg *pmsg)
writew(val, i2c->base + VIAI2C_REG_CR);
}

while (xfer_len < pmsg->len) {
ret = viai2c_check_status(i2c);
if (ret)
return ret;

pmsg->buf[xfer_len] = readw(i2c->base + VIAI2C_REG_CDR) >> 8;
xfer_len++;

val = readw(i2c->base + VIAI2C_REG_CR) | VIAI2C_CR_CPU_RDY;
if (xfer_len == pmsg->len - 1)
val |= VIAI2C_CR_RX_END;
writew(val, i2c->base + VIAI2C_REG_CR);
}
if (!wait_for_completion_timeout(&i2c->complete, VIAI2C_TIMEOUT))
return -ETIMEDOUT;

return 0;
return i2c->ret;
}

int viai2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
Expand All @@ -165,6 +108,9 @@ int viai2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
return ret;
}

i2c->msg = pmsg;
i2c->xfered_len = 0;

if (pmsg->flags & I2C_M_RD)
ret = viai2c_read(i2c, pmsg);
else
Expand All @@ -174,15 +120,76 @@ int viai2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
return (ret < 0) ? ret : i;
}

/*
* Main process of the byte mode xfer
*
* Return value indicates whether the transfer is complete
* 1: all the data has been successfully transferred
* 0: there is still data that needs to be transferred
* -EIO: error occurred
*/
static int viai2c_irq_xfer(struct viai2c *i2c)
{
u16 val;
struct i2c_msg *msg = i2c->msg;
u8 read = msg->flags & I2C_M_RD;
void __iomem *base = i2c->base;

if (read) {
msg->buf[i2c->xfered_len] = readw(base + VIAI2C_REG_CDR) >> 8;

val = readw(base + VIAI2C_REG_CR) | VIAI2C_CR_CPU_RDY;
if (i2c->xfered_len == msg->len - 2)
val |= VIAI2C_CR_RX_END;
writew(val, base + VIAI2C_REG_CR);
} else {
val = readw(base + VIAI2C_REG_CSR);
if (val & VIAI2C_CSR_RCV_NOT_ACK)
return -EIO;

/* I2C_SMBUS_QUICK */
if (msg->len == 0) {
val = VIAI2C_CR_TX_END | VIAI2C_CR_CPU_RDY | VIAI2C_CR_ENABLE;
writew(val, base + VIAI2C_REG_CR);
return 1;
}

if ((i2c->xfered_len + 1) == msg->len) {
if (!i2c->last)
writew(VIAI2C_CR_ENABLE, base + VIAI2C_REG_CR);
} else {
writew(msg->buf[i2c->xfered_len + 1] & 0xFF, base + VIAI2C_REG_CDR);
writew(VIAI2C_CR_CPU_RDY | VIAI2C_CR_ENABLE, base + VIAI2C_REG_CR);
}
}

i2c->xfered_len++;

return i2c->xfered_len == msg->len;
}

static irqreturn_t viai2c_isr(int irq, void *data)
{
struct viai2c *i2c = data;
u8 status;

/* save the status and write-clear it */
i2c->cmd_status = readw(i2c->base + VIAI2C_REG_ISR);
writew(i2c->cmd_status, i2c->base + VIAI2C_REG_ISR);
status = readw(i2c->base + VIAI2C_REG_ISR);
writew(status, i2c->base + VIAI2C_REG_ISR);

i2c->ret = 0;
if (status & VIAI2C_ISR_NACK_ADDR)
i2c->ret = -EIO;

if (status & VIAI2C_ISR_SCL_TIMEOUT)
i2c->ret = -ETIMEDOUT;

if (!i2c->ret)
i2c->ret = viai2c_irq_xfer(i2c);

complete(&i2c->complete);
/* All the data has been successfully transferred or error occurred */
if (i2c->ret)
complete(&i2c->complete);

return IRQ_HANDLED;
}
Expand Down
6 changes: 4 additions & 2 deletions drivers/i2c/busses/i2c-viai2c-common.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -58,11 +58,13 @@ struct viai2c {
struct clk *clk;
u16 tcr;
int irq;
u16 cmd_status;
u16 xfered_len;
struct i2c_msg *msg;
int ret;
bool last;
};

int viai2c_wait_bus_not_busy(struct viai2c *i2c);
int viai2c_check_status(struct viai2c *i2c);
int viai2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num);
int viai2c_init(struct platform_device *pdev, struct viai2c **pi2c);

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