--- /dev/null
+From 714580d7c11f81afb5e08c71f79a03a1ed4ae44e Mon Sep 17 00:00:00 2001
+From: Jean-Francois Dagenais <jeff.dagenais@gmail.com>
+Date: Thu, 28 Mar 2019 12:41:11 -0400
+Subject: [PATCH] w1: ds2408: reset on output_write retry with readback
+
+commit 49695ac46861180baf2b2b92c62da8619b6bf28f upstream.
+
+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>
+---
+ drivers/w1/slaves/w1_ds2408.c | 76 ++++++++++++++++++-----------------
+ 1 file changed, 39 insertions(+), 37 deletions(-)
+
+--- a/drivers/w1/slaves/w1_ds2408.c
++++ b/drivers/w1/slaves/w1_ds2408.c
+@@ -138,14 +138,37 @@ static ssize_t status_control_read(struc
+ 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
+ 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);
++ w1_write_block(sl->master, w1_buf, 3);
+
+- if (readBack != W1_F29_SUCCESS_CONFIRM_BYTE) {
+- if (w1_reset_resume_command(sl->master))
+- goto error;
+- /* try again, the slave is ready for a command */
+- continue;
++ if (w1_read_8(sl->master) == W1_F29_SUCCESS_CONFIRM_BYTE &&
++ optional_read_back_valid(sl, *buf)) {
++ bytes_written = 1;
++ goto out;
+ }
+
+-#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;
++ goto out; /* unrecoverable error */
++ /* try again, the slave is ready for a command */
++ } while (--retries);
+
+- /* 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! */
+- mutex_unlock(&sl->master->bus_mutex);
+- dev_dbg(&sl->dev,
+- "mutex unlocked, retries:%d", retries);
+- return 1;
+- }
+- }
+-error:
++out:
+ 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;
+ }
+
+
projects / openwrt / staging / chunkeey.git / blobdiff