From 6a158c0de791a81eb761ccf26ead1bd0834abac2 Mon Sep 17 00:00:00 2001 From: David Fries Date: Wed, 15 Oct 2008 22:04:42 -0700 Subject: W1: feature, enable hardware strong pullup Add a strong pullup option to the w1 system. This supplies extra power for parasite powered devices. There is a w1_master_pullup sysfs entry and enable_pullup module parameter to enable or disable the strong pullup. The one wire bus requires at a minimum one wire and ground. The common wire is used for sending and receiving data as well as supplying power to devices that are parasite powered of which temperature sensors can be one example. The bus must be idle and left high while a temperature conversion is in progress, in addition the normal pullup resister on larger networks or even higher temperatures might not supply enough power. The pullup resister can't provide too much pullup current, because devices need to pull the bus down to write a value. This enables the strong pullup for supported hardware, which can supply more current when requested. Unsupported hardware will just delay with the bus high. The hardware USB 2490 one wire bus master has a bit on some commands which will enable the strong pullup as soon as the command finishes executing. To use strong pullup, call the new w1_next_pullup function to register the duration. The next write command will call set_pullup before sending the data, and reset the duration to zero once it returns. Switched from simple_strtol to strict_strtol. Signed-off-by: David Fries Cc: Evgeniy Polyakov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/w1/w1_io.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 64 insertions(+), 4 deletions(-) (limited to 'drivers/w1/w1_io.c') diff --git a/drivers/w1/w1_io.c b/drivers/w1/w1_io.c index 0056ef69009..97b338a16ab 100644 --- a/drivers/w1/w1_io.c +++ b/drivers/w1/w1_io.c @@ -92,6 +92,40 @@ static void w1_write_bit(struct w1_master *dev, int bit) } } +/** + * Pre-write operation, currently only supporting strong pullups. + * Program the hardware for a strong pullup, if one has been requested and + * the hardware supports it. + * + * @param dev the master device + */ +static void w1_pre_write(struct w1_master *dev) +{ + if (dev->pullup_duration && + dev->enable_pullup && dev->bus_master->set_pullup) { + dev->bus_master->set_pullup(dev->bus_master->data, + dev->pullup_duration); + } +} + +/** + * Post-write operation, currently only supporting strong pullups. + * If a strong pullup was requested, clear it if the hardware supports + * them, or execute the delay otherwise, in either case clear the request. + * + * @param dev the master device + */ +static void w1_post_write(struct w1_master *dev) +{ + if (dev->pullup_duration) { + if (dev->enable_pullup && dev->bus_master->set_pullup) + dev->bus_master->set_pullup(dev->bus_master->data, 0); + else + msleep(dev->pullup_duration); + dev->pullup_duration = 0; + } +} + /** * Writes 8 bits. * @@ -102,11 +136,17 @@ void w1_write_8(struct w1_master *dev, u8 byte) { int i; - if (dev->bus_master->write_byte) + if (dev->bus_master->write_byte) { + w1_pre_write(dev); dev->bus_master->write_byte(dev->bus_master->data, byte); + } else - for (i = 0; i < 8; ++i) + for (i = 0; i < 8; ++i) { + if (i == 7) + w1_pre_write(dev); w1_touch_bit(dev, (byte >> i) & 0x1); + } + w1_post_write(dev); } EXPORT_SYMBOL_GPL(w1_write_8); @@ -203,11 +243,14 @@ void w1_write_block(struct w1_master *dev, const u8 *buf, int len) { int i; - if (dev->bus_master->write_block) + if (dev->bus_master->write_block) { + w1_pre_write(dev); dev->bus_master->write_block(dev->bus_master->data, buf, len); + } else for (i = 0; i < len; ++i) - w1_write_8(dev, buf[i]); + w1_write_8(dev, buf[i]); /* calls w1_pre_write */ + w1_post_write(dev); } EXPORT_SYMBOL_GPL(w1_write_block); @@ -306,3 +349,20 @@ int w1_reset_select_slave(struct w1_slave *sl) return 0; } EXPORT_SYMBOL_GPL(w1_reset_select_slave); + +/** + * 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 + * write operation without a strong pullup. This is a one shot request for + * the next write, specifying zero will clear a previous request. + * The w1 master lock must be held. + * + * @param delay time in milliseconds + * @return 0=success, anything else=error + */ +void w1_next_pullup(struct w1_master *dev, int delay) +{ + dev->pullup_duration = delay; +} +EXPORT_SYMBOL_GPL(w1_next_pullup); -- cgit v1.2.3-18-g5258