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>
This commit is contained in:
Jean-François Dagenais 2011-05-26 16:26:01 -07:00 committed by Linus Torvalds
parent 6f7bd76f05
commit 67dfd54c2d
2 changed files with 28 additions and 0 deletions

View File

@ -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)

View File

@ -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