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w1: ds2408: reset on output_write retry with readback

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When we have success in 'Channel Access Write' but reading back latch
states fails, a write is retried without doing a proper slave reset.
This leads to protocol errors as the slave treats the next 'Channel
Access Write' as the continuation of previous command.

This commit is fixing this by making sure if the retry loop re-runs, a
reset is performed, whatever the failure (CONFIRM_BYTE or the read
back).

The loop was quite due for a cleanup and this change mandated it. By
isolating the CONFIG_W1_SLAVE_DS2408_READBACK case into it's own
function, we vastly reduce the visual and branching(runtime and
compile-time) noise.

Reported-by: Mariusz Bialonczyk <manio@skyboo.net>
Tested-by: Mariusz Bialonczyk <manio@skyboo.net>
Signed-off-by: Jean-Francois Dagenais <jeff.dagenais@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jean-Francois Dagenais 2019-03-28 12:41:11 -04:00 committed by Greg Kroah-Hartman
parent b909ef83ed
commit 49695ac468
1 changed files with 39 additions and 37 deletions
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76
drivers/w1/slaves/w1_ds2408.c
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@ -138,14 +138,37 @@ static ssize_t status_control_read(struct file *filp, struct kobject *kobj,
W1_F29_REG_CONTROL_AND_STATUS, buf);
}
#ifdef fCONFIG_W1_SLAVE_DS2408_READBACK
static bool optional_read_back_valid(struct w1_slave *sl, u8 expected)
{
u8 w1_buf[3];
if (w1_reset_resume_command(sl->master))
return false;
w1_buf[0] = W1_F29_FUNC_READ_PIO_REGS;
w1_buf[1] = W1_F29_REG_OUTPUT_LATCH_STATE;
w1_buf[2] = 0;
w1_write_block(sl->master, w1_buf, 3);
return (w1_read_8(sl->master) == expected);
}
#else
static bool optional_read_back_valid(struct w1_slave *sl, u8 expected)
{
return true;
}
#endif
static ssize_t output_write(struct file *filp, struct kobject *kobj,
struct bin_attribute *bin_attr, char *buf,
loff_t off, size_t count)
{
struct w1_slave *sl = kobj_to_w1_slave(kobj);
u8 w1_buf[3];
u8 readBack;
unsigned int retries = W1_F29_RETRIES;
ssize_t bytes_written = -EIO;
if (count != 1 || off != 0)
return -EFAULT;
@ -155,54 +178,33 @@ static ssize_t output_write(struct file *filp, struct kobject *kobj,
dev_dbg(&sl->dev, "mutex locked");
if (w1_reset_select_slave(sl))
goto error;
goto out;
while (retries--) {
do {
w1_buf[0] = W1_F29_FUNC_CHANN_ACCESS_WRITE;
w1_buf[1] = *buf;
w1_buf[2] = ~(*buf);
w1_write_block(sl->master, w1_buf, 3);
readBack = w1_read_8(sl->master);
if (w1_read_8(sl->master) == W1_F29_SUCCESS_CONFIRM_BYTE &&
optional_read_back_valid(sl, *buf)) {
bytes_written = 1;
goto out;
}
if (readBack != W1_F29_SUCCESS_CONFIRM_BYTE) {
if (w1_reset_resume_command(sl->master))
goto error;
goto out; /* unrecoverable error */
/* try again, the slave is ready for a command */
continue;
}
} while (--retries);
#ifdef CONFIG_W1_SLAVE_DS2408_READBACK
/* here the master could read another byte which
would be the PIO reg (the actual pin logic state)
since in this driver we don't know which pins are
in and outs, there's no value to read the state and
compare. with (*buf) so end this command abruptly: */
if (w1_reset_resume_command(sl->master))
goto error;
/* go read back the output latches */
/* (the direct effect of the write above) */
w1_buf[0] = W1_F29_FUNC_READ_PIO_REGS;
w1_buf[1] = W1_F29_REG_OUTPUT_LATCH_STATE;
w1_buf[2] = 0;
w1_write_block(sl->master, w1_buf, 3);
/* read the result of the READ_PIO_REGS command */
if (w1_read_8(sl->master) == *buf)
#endif
{
/* success! */
out:
mutex_unlock(&sl->master->bus_mutex);
dev_dbg(&sl->dev,
"mutex unlocked, retries:%d", retries);
return 1;
}
}
error:
mutex_unlock(&sl->master->bus_mutex);
dev_dbg(&sl->dev, "mutex unlocked in error, retries:%d", retries);
return -EIO;
dev_dbg(&sl->dev, "%s, mutex unlocked retries:%d\n",
(bytes_written > 0) ? "succeeded" : "error", retries);
return bytes_written;
}