On Thu, Mar 24, 2011 at 1:04 AM, Magnus Damm <magnus.damm@xxxxxxxxx> wrote: > On Wed, Mar 23, 2011 at 1:59 AM, Mark Brown > <broonie@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote: >> On Wed, Mar 23, 2011 at 01:51:02AM +0900, Magnus Damm wrote: >> >>> I'm not sure if this is i2c specific though - in general you probably >>> need to register the parent bus driver first. >> >> This was my original question - I'm not aware of any reason why you >> should need to register the driver for the specific bus first, it seems >> odd. > > Can't see why it wouldn't work - in theory at least. I'll have a look tomorrow. Ok, it seems like the I2C bus registration is working as expected. After digging into this a bit more I've discovered that the root cause seems to be related to clocks. On sh7372 the I2C controller and the serial console share the parent clock, and the setup order is affecting the serial console. Without this patch, if subsys_init() is used for tca6416-keypad then the I2C controller will be used at probe() time from the function tca6416_setup_registers() - this before the serial console driver has been initialized properly. The I2C controller used by tca6416 will stop the parent clock when the I2C bus access is finished. The serial console driver is driven early using earlyprintk at this time, and the clock is assumed to be enabled until the real driver is installed at module_init() time. So with subsys_init() in tca6416 the I2C controller stops the clock while the earlyprintk code assumes it to be on. This is causing delays. If the tca6416 driver is changed to module_init() then the serial console driver will be initialized before the tca6416 driver due to the linking order and all is working fine. As we already knew, the clock framework code in drivers/sh/clk should be updated to turn off unused clocks. To fix the issue in this mail thread we should also update the code to force the console clock to be enabled early on to make sure the serial console clock isn't turned off by accident. I propose that we convert the tca6416 driver to module_init() as a short term fix _and_ at the same time work on improving the clock framework code. Can anyone think of a reason why the tca6416 driver shouldn't be changed to module_init()? Thanks, / magnus -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
