On Wed, Sep 14, 2016 at 10:42:50AM -0700, Stephen Boyd wrote: > > > > > > Hmm.. maybe the confusion is in which registers we should be able to > > > access? Are we talking about the ULPI viewport MMIO register space or > > > the ULPI registers that we access through the viewport? I have a > > > hw_phymode_configure() inside of of ci_ulpi_init() so that the > > > identification registers through the ULPI viewport read properly > > > (assuming there aren't other power requirements like regulators). If we > > > don't set the portsc.pts before using the viewport, the viewport doesn't > > > work and reads timeout. So we really don't touch the ULPI registers > > > except for the scratch space and the id registers until after the phy is > > > properly powered on with clks and regulators, because the only place we > > > touch them after doing the id checking is in this phy driver in > > > qcom_usb_hs_phy_power_on(). We've "solved" the chicken-egg problem where > > > we don't know which device driver to probe because the phy needs to be > > > powered on to read the id registers to know which device driver to use > > > by using DT to match up device drivers instead. > > > > > > [1] https://www.sparkfun.com/datasheets/Components/SMD/ULPI_v1_1.pdf > > > > Ok, ulpi phy works like USB device on USB bus which create device at > > runtime. So, like some hard-wired USB devices, it may needs power > > sequence too, otherwise, how it knows which driver can loads. > > > > Yes. We use the DT compatible string to ignore any issues with reading > the device ids when the device is powered off. Unlike USB though, we > have device drivers for the ULPI PHYs that do the power sequencing along > with other initializations, so using a common pwrseq layer seems like > overkill just so we can read the id registers. If the attempt to read id registers will not hang the system, it can work. Like the case [1], without PHY ref_clk, it will hang when configure PHY mode (visit portsc.pts), it has no chance to read id registers. So, I still think the ULPI bus driver needs to do power sequence for its children, unless you have some place to open the ref_clk. > > Are there any concerns with this patch? Or can they be reapplied? For this patch, it is ok for me. [1] http://www.spinics.net/lists/linux-usb/msg146336.html -- Best Regards, Peter Chen -- 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
