Commit 67dfd54c authored May 26, 2011 by Jean-François Dagenais Committed by Linus Torvalds May 26, 2011

w1: add 1-wire (w1) reset and resume command API support



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>

parent 6f7bd76f

drivers/w1/w1.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -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)

drivers/w1/w1_io.c

+26 −0

Original line number	Diff line number	Diff line
		@@ -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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