From 67dfd54c2d83a76a5756760f7fee0c8cfac52b1c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jean-Fran=C3=A7ois=20Dagenais?= <dagenaisj@sonatest.com>
Date: Thu, 26 May 2011 16:26:01 -0700
Subject: [PATCH] w1: add 1-wire (w1) reset and resume command API support
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The first patch adds generic functionnality to w1_io for Resume Command
[A5h] lots of slaves support. I found it useful for multi-commands/reset
workflows with the same slave on a multi-slave bus.
This DS2408 w1 slave driver is not complete for all the features of the
chip, but its sufficient if you use it as a simple IO expander. Enjoy!
The ds1wm had Kconfig dependencies towards ARM && HAVE_CLK. I took them
out since I was using the ds1wm on an x86_64 platform (ds1wm in a FPGA
through pcie) and found them irrelevant.
The clock freq/divisors at the top of ds1wm.c did not have the MSB set to
1. This bit is CLK_EN which turns the whole prescaler and dividers on.
The driver never mentionned this bit either, so I just included this bit
right in the table entries. I also took the liberty to add a couple of
entries to the table. The spec doesn't explicitely mentions these
possibilities but the description and examination of the core shows the
prescalers & dividers can be used for more than the table explicitely
shows. The table I enlarged still doesn't cover all possibilities, but
it's a good start.
I also made a few tweaks to a couple of the read and write algorithms
which made sense while I had my head very deep in the ds1wm documentation.
We stressed it a lot with 10+ slaves on the bus, many ds2408, ds2431 and
ds2433 at the same time doing extensive interaction. It proved quite
stable in our production environment.
This patch:
Add generic functionnality to w1_io for Resume Command [A5h] lots of
slaves support.
Signed-off-by: Jean-François Dagenais <dagenaisj@sonatest.com>
Cc: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Cc: Szabolcs Gyurko <szabolcs.gyurko@tlt.hu>
Cc: Matt Reimer <mreimer@vpop.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
drivers/w1/w1.h | 2 ++
drivers/w1/w1_io.c | 26 ++++++++++++++++++++++++++
2 files changed, 28 insertions(+)
diff --git a/drivers/w1/w1.h b/drivers/w1/w1.h
index d8a9709f3449..f804eba89b7b 100644
--- a/drivers/w1/w1.h
+++ b/drivers/w1/w1.h
@@ -55,6 +55,7 @@ struct w1_reg_num
#define W1_READ_ROM 0x33
#define W1_READ_PSUPPLY 0xB4
#define W1_MATCH_ROM 0x55
+#define W1_RESUME_CMD 0xA5
#define W1_SLAVE_ACTIVE 0
@@ -213,6 +214,7 @@ void w1_write_block(struct w1_master *, const u8 *, int);
void w1_touch_block(struct w1_master *, u8 *, int);
u8 w1_read_block(struct w1_master *, u8 *, int);
int w1_reset_select_slave(struct w1_slave *sl);
+int w1_reset_resume_command(struct w1_master *);
void w1_next_pullup(struct w1_master *, int);
static inline struct w1_slave* dev_to_w1_slave(struct device *dev)
diff --git a/drivers/w1/w1_io.c b/drivers/w1/w1_io.c
index 3ebe9726a9e5..8e8b64cfafb6 100644
--- a/drivers/w1/w1_io.c
+++ b/drivers/w1/w1_io.c
@@ -389,6 +389,32 @@ int w1_reset_select_slave(struct w1_slave *sl)
}
EXPORT_SYMBOL_GPL(w1_reset_select_slave);
+/**
+ * When the workflow with a slave amongst many requires several
+ * successive commands a reset between each, this function is similar
+ * to doing a reset then a match ROM for the last matched ROM. The
+ * advantage being that the matched ROM step is skipped in favor of the
+ * resume command. The slave must support the command of course.
+ *
+ * If the bus has only one slave, traditionnaly the match ROM is skipped
+ * and a "SKIP ROM" is done for efficiency. On multi-slave busses, this
+ * doesn't work of course, but the resume command is the next best thing.
+ *
+ * The w1 master lock must be held.
+ *
+ * @param dev the master device
+ */
+int w1_reset_resume_command(struct w1_master *dev)
+{
+ if (w1_reset_bus(dev))
+ return -1;
+
+ /* This will make only the last matched slave perform a skip ROM. */
+ w1_write_8(dev, W1_RESUME_CMD);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(w1_reset_resume_command);
+
/**
* Put out a strong pull-up of the specified duration after the next write
* operation. Not all hardware supports strong pullups. Hardware that
--
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