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authorJean-François Dagenais <dagenaisj@sonatest.com>2011-05-26 16:26:01 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-05-26 17:12:38 -0700
commit67dfd54c2d83a76a5756760f7fee0c8cfac52b1c (patch)
tree67f60d8bf1fcfd64106e419c1de3cd6e5618dd1d /drivers/w1/w1_io.c
parent6f7bd76f05eb2bfbb48d58c0408a50a7e16b2423 (diff)
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>
Diffstat (limited to 'drivers/w1/w1_io.c')
-rw-r--r--drivers/w1/w1_io.c26
1 files changed, 26 insertions, 0 deletions
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
@@ -390,6 +390,32 @@ 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
* doesn't support strong pullups will sleep for the given time after the