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141 lines
4.2 KiB
Diff
141 lines
4.2 KiB
Diff
From 714580d7c11f81afb5e08c71f79a03a1ed4ae44e Mon Sep 17 00:00:00 2001
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From: Jean-Francois Dagenais <jeff.dagenais@gmail.com>
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Date: Thu, 28 Mar 2019 12:41:11 -0400
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Subject: [PATCH] w1: ds2408: reset on output_write retry with readback
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commit 49695ac46861180baf2b2b92c62da8619b6bf28f upstream.
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When we have success in 'Channel Access Write' but reading back latch
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states fails, a write is retried without doing a proper slave reset.
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This leads to protocol errors as the slave treats the next 'Channel
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Access Write' as the continuation of previous command.
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This commit is fixing this by making sure if the retry loop re-runs, a
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reset is performed, whatever the failure (CONFIRM_BYTE or the read
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back).
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The loop was quite due for a cleanup and this change mandated it. By
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isolating the CONFIG_W1_SLAVE_DS2408_READBACK case into it's own
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function, we vastly reduce the visual and branching(runtime and
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compile-time) noise.
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Reported-by: Mariusz Bialonczyk <manio@skyboo.net>
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Tested-by: Mariusz Bialonczyk <manio@skyboo.net>
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Signed-off-by: Jean-Francois Dagenais <jeff.dagenais@gmail.com>
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Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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---
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drivers/w1/slaves/w1_ds2408.c | 76 ++++++++++++++++++-----------------
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1 file changed, 39 insertions(+), 37 deletions(-)
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--- a/drivers/w1/slaves/w1_ds2408.c
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+++ b/drivers/w1/slaves/w1_ds2408.c
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@@ -138,14 +138,37 @@ static ssize_t status_control_read(struc
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W1_F29_REG_CONTROL_AND_STATUS, buf);
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}
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+#ifdef fCONFIG_W1_SLAVE_DS2408_READBACK
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+static bool optional_read_back_valid(struct w1_slave *sl, u8 expected)
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+{
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+ u8 w1_buf[3];
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+
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+ if (w1_reset_resume_command(sl->master))
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+ return false;
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+
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+ w1_buf[0] = W1_F29_FUNC_READ_PIO_REGS;
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+ w1_buf[1] = W1_F29_REG_OUTPUT_LATCH_STATE;
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+ w1_buf[2] = 0;
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+
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+ w1_write_block(sl->master, w1_buf, 3);
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+
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+ return (w1_read_8(sl->master) == expected);
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+}
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+#else
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+static bool optional_read_back_valid(struct w1_slave *sl, u8 expected)
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+{
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+ return true;
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+}
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+#endif
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+
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static ssize_t output_write(struct file *filp, struct kobject *kobj,
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struct bin_attribute *bin_attr, char *buf,
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loff_t off, size_t count)
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{
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struct w1_slave *sl = kobj_to_w1_slave(kobj);
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u8 w1_buf[3];
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- u8 readBack;
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unsigned int retries = W1_F29_RETRIES;
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+ ssize_t bytes_written = -EIO;
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if (count != 1 || off != 0)
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return -EFAULT;
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@@ -155,54 +178,33 @@ static ssize_t output_write(struct file
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dev_dbg(&sl->dev, "mutex locked");
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if (w1_reset_select_slave(sl))
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- goto error;
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+ goto out;
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- while (retries--) {
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+ do {
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w1_buf[0] = W1_F29_FUNC_CHANN_ACCESS_WRITE;
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w1_buf[1] = *buf;
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w1_buf[2] = ~(*buf);
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- w1_write_block(sl->master, w1_buf, 3);
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- readBack = w1_read_8(sl->master);
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+ w1_write_block(sl->master, w1_buf, 3);
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- if (readBack != W1_F29_SUCCESS_CONFIRM_BYTE) {
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- if (w1_reset_resume_command(sl->master))
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- goto error;
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- /* try again, the slave is ready for a command */
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- continue;
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+ if (w1_read_8(sl->master) == W1_F29_SUCCESS_CONFIRM_BYTE &&
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+ optional_read_back_valid(sl, *buf)) {
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+ bytes_written = 1;
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+ goto out;
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}
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-#ifdef CONFIG_W1_SLAVE_DS2408_READBACK
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- /* here the master could read another byte which
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- would be the PIO reg (the actual pin logic state)
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- since in this driver we don't know which pins are
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- in and outs, there's no value to read the state and
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- compare. with (*buf) so end this command abruptly: */
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if (w1_reset_resume_command(sl->master))
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- goto error;
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+ goto out; /* unrecoverable error */
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+ /* try again, the slave is ready for a command */
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+ } while (--retries);
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- /* go read back the output latches */
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- /* (the direct effect of the write above) */
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- w1_buf[0] = W1_F29_FUNC_READ_PIO_REGS;
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- w1_buf[1] = W1_F29_REG_OUTPUT_LATCH_STATE;
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- w1_buf[2] = 0;
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- w1_write_block(sl->master, w1_buf, 3);
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- /* read the result of the READ_PIO_REGS command */
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- if (w1_read_8(sl->master) == *buf)
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-#endif
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- {
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- /* success! */
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- mutex_unlock(&sl->master->bus_mutex);
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- dev_dbg(&sl->dev,
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- "mutex unlocked, retries:%d", retries);
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- return 1;
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- }
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- }
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-error:
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+out:
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mutex_unlock(&sl->master->bus_mutex);
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- dev_dbg(&sl->dev, "mutex unlocked in error, retries:%d", retries);
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- return -EIO;
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+ dev_dbg(&sl->dev, "%s, mutex unlocked retries:%d\n",
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+ (bytes_written > 0) ? "succeeded" : "error", retries);
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+
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+ return bytes_written;
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}
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