From 67dfd54c2d83a76a5756760f7fee0c8cfac52b1c Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Jean-Fran=C3=A7ois=20Dagenais?= Date: Thu, 26 May 2011 16:26:01 -0700 Subject: w1: add 1-wire (w1) reset and resume command API support MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Cc: Evgeniy Polyakov Cc: Szabolcs Gyurko Cc: Matt Reimer Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/w1/w1.h | 2 ++ drivers/w1/w1_io.c | 26 ++++++++++++++++++++++++++ 2 files changed, 28 insertions(+) (limited to 'drivers') 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 -- cgit v1.2.3