On Thu, Nov 14, 2013 at 03:00:25PM -0200, Fabio Estevam wrote: > Hi Michael, > > On 11/14/2013 02:53 PM, Michael Grzeschik wrote: > >Hi Fabio, > > > >On Thu, Nov 14, 2013 at 02:12:25PM -0200, Fabio Estevam wrote: > >>When using an external USB hub, it is common that they require a clock input. > >> > >>Add a 'clk_usb' clock, so that it can be retrieved from the device tree and > >>enabled in the driver, so that the clock can properly drive the external > >>USB hub. > >> > >>Tested on a imx6q-udoo board, that connects via USBH1 to a USB2514 hub. > >> > >>In this board the USB2514 is clocked from a 24MHz clock that comes from the > >>imx6q CLKO2 pin. > > > >what kind of hub is this? Why does it need an extra clock line? Usually > >only a phy needs an extra clock line. > > Here is the USB hub chip that mx6q udoo board uses: > http://ww1.microchip.com/downloads/en/DeviceDoc/251xb.pdf > > (Search for "external 24MHz clock") So, what I see is an regular Hub that usually got driven by an external Crystal of 24MHz. That the boarddesigner did change that to be driven by the SoC clock makes your dependency here. We need an location for this, but obviously not in the glue. I could think of an simple bus driver that has i2c, regulator and clock dependency in the device tree. But where this got implemented is currently undefined. Thanks, Michael -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
