From 844aff82a6599a8d96545dfb89663809e71719fc Mon Sep 17 00:00:00 2001 From: Ian Lepore Date: Tue, 18 Nov 2014 01:54:31 +0000 Subject: Allow i2c bus speed to be configured via hints, FDT data, and sysctl. The current support for controlling i2c bus speed is an inconsistant mess. There are 4 symbolic speed values defined, UNKNOWN, SLOW, FAST, FASTEST. It seems to be universally assumed that SLOW means the standard 100KHz rate from the original spec. Nothing ever calls iicbus_reset() with a speed of FAST, although some drivers would treat it as the 400KHz standard speed. Mostly iicbus_reset() is called with the speed set to UNKNOWN or FASTEST, and there's really no telling what any individual driver will do with those. The speed of an i2c bus is limited by the speed of the slowest device on the bus. This means that generally the bus speed needs to be configured based on the board/system and the components within it. Historically for i2c we've configured with device hints. Newer systems use FDT data and it documents a clock-frequency property for i2c busses. Hobbyists and developers are likely to want on the fly changes. These changes provide all 3 methods, but do not require any existing drivers to change to use the new facilities. This adds an iicbus method, iicbus_get_frequency(dev, speed) that gets the frequency for the requested symbolic speed. If the symbolic speed is SLOW or if there is no speed configured for the bus, the returned value is 100KHz, always. Otherwise, if bus speed is configured by hints, fdt, tunable, or sysctl, that speed is returned. It also adds a helper function, iicbus_init_frequency() that any bus driver subclassed from iicbus can initialize the frequency from some other source of info. Initial driver implementations are provided for Freescale and TI. Differential Revision: https://reviews.freebsd.org/D1174 PR: 195009 --- sys/dev/ofw/ofw_iicbus.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) (limited to 'sys/dev/ofw') diff --git a/sys/dev/ofw/ofw_iicbus.c b/sys/dev/ofw/ofw_iicbus.c index 1574f6e9674a..f6d1be58612f 100644 --- a/sys/dev/ofw/ofw_iicbus.c +++ b/sys/dev/ofw/ofw_iicbus.c @@ -101,12 +101,24 @@ ofw_iicbus_attach(device_t dev) { struct iicbus_softc *sc = IICBUS_SOFTC(dev); struct ofw_iicbus_devinfo *dinfo; - phandle_t child; - pcell_t paddr; + phandle_t child, node; + pcell_t freq, paddr; device_t childdev; sc->dev = dev; mtx_init(&sc->lock, "iicbus", NULL, MTX_DEF); + + /* + * If there is a clock-frequency property for the device node, use it as + * the starting value for the bus frequency. Then call the common + * routine that handles the tunable/sysctl which allows the FDT value to + * be overridden by the user. + */ + node = ofw_bus_get_node(dev); + freq = 0; + OF_getencprop(node, "clock-frequency", &freq, sizeof(freq)); + iicbus_init_frequency(dev, freq); + iicbus_reset(dev, IIC_FASTEST, 0, NULL); bus_generic_probe(dev); @@ -115,8 +127,7 @@ ofw_iicbus_attach(device_t dev) /* * Attach those children represented in the device tree. */ - for (child = OF_child(ofw_bus_get_node(dev)); child != 0; - child = OF_peer(child)) { + for (child = OF_child(node); child != 0; child = OF_peer(child)) { /* * Try to get the I2C address first from the i2c-address * property, then try the reg property. It moves around -- cgit v1.2.3