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>
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@ -55,6 +55,7 @@ struct w1_reg_num
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#define W1_READ_ROM 0x33
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#define W1_READ_PSUPPLY 0xB4
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#define W1_MATCH_ROM 0x55
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#define W1_RESUME_CMD 0xA5
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#define W1_SLAVE_ACTIVE 0
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@ -213,6 +214,7 @@ void w1_write_block(struct w1_master *, const u8 *, int);
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void w1_touch_block(struct w1_master *, u8 *, int);
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u8 w1_read_block(struct w1_master *, u8 *, int);
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int w1_reset_select_slave(struct w1_slave *sl);
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int w1_reset_resume_command(struct w1_master *);
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void w1_next_pullup(struct w1_master *, int);
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static inline struct w1_slave* dev_to_w1_slave(struct device *dev)
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@ -389,6 +389,32 @@ int w1_reset_select_slave(struct w1_slave *sl)
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}
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EXPORT_SYMBOL_GPL(w1_reset_select_slave);
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/**
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* When the workflow with a slave amongst many requires several
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* successive commands a reset between each, this function is similar
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* to doing a reset then a match ROM for the last matched ROM. The
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* advantage being that the matched ROM step is skipped in favor of the
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* resume command. The slave must support the command of course.
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*
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* If the bus has only one slave, traditionnaly the match ROM is skipped
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* and a "SKIP ROM" is done for efficiency. On multi-slave busses, this
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* doesn't work of course, but the resume command is the next best thing.
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*
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* The w1 master lock must be held.
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*
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* @param dev the master device
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*/
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int w1_reset_resume_command(struct w1_master *dev)
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{
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if (w1_reset_bus(dev))
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return -1;
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/* This will make only the last matched slave perform a skip ROM. */
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w1_write_8(dev, W1_RESUME_CMD);
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return 0;
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}
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EXPORT_SYMBOL_GPL(w1_reset_resume_command);
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/**
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* Put out a strong pull-up of the specified duration after the next write
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* operation. Not all hardware supports strong pullups. Hardware that
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