Hi Shimoda-san, On Mon, Jul 24, 2017 at 12:33 PM, Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx> wrote: >> From: Geert Uytterhoeven >> Sent: Wednesday, July 5, 2017 9:22 PM >> On Wed, Jul 5, 2017 at 1:57 PM, Yoshihiro Shimoda >> <yoshihiro.shimoda.uh@xxxxxxxxxxx> wrote: >> >> From: Geert Uytterhoeven >> >> Sent: Wednesday, July 5, 2017 7:09 PM >> >> On Wed, Jun 28, 2017 at 8:28 AM, Yoshihiro Shimoda >> >> <yoshihiro.shimoda.uh@xxxxxxxxxxx> wrote: >> >> > R-Car USB 2.0 controller can change the clock source from an oscillator >> >> > to an external clock via a register. So, this patch adds support >> >> > the clock source selector as a clock driver. >> >> >> > --- /dev/null >> >> > +++ b/drivers/clk/renesas/rcar-usb2-clock-sel.c >> >> >> > +/* Since this driver needs other ccf drivers, this uses subsys_initcall_sync */ >> >> > +subsys_initcall_sync(rcar_usb2_clock_sel_init); >> >> >> >> I suppose this is a workaround for the lack of probe deferral support in the >> >> USB subsystem? >> > >> > This is my fault. I added "power-domains" property into this device's node. >> > After I remove the power-domains like the cpg node, this driver can use subsys_initcall() >> > instead of subsys_initcall_sync(). >> >> Does the clock sel module requires the functional clock "ehci_ohci" to be >> running before you can access its registers? >> If yes, I think there should be a "power-domains" property. > > Yes. But... > >> Then, you can simplify the code by calling >> >> pm_runtime_enable(dev); >> pm_runtime_get_sync(dev); >> >> and remove the explicit handling of the functional clock. >> >> That does not solve probe deferral handling in the USB subsystem, though. > > I added a debug message at end of cpg_mssr_probe(), and if I used subsys_initcall() on > rcar-usb2-clock-sel driver, kernel log output below: > ======================== > [ 0.272547] rcar-usb2-clock-sel e6590630.clock-controller: probe deferral not supported > [ 0.273944] ----------------- cpg_mssr_probe: probed! > ======================== > So, it seems the renesas-cpg-mssr.c doesn't solve probe deferral handling. > (The driver renesas-cpg-mssr.c uses platform_driver_probe() for now.) > > So, IIUC, this rcar-usb2-clock-sel driver cannot use subsys_initcall(). > Or, should we modify the renesas-cpg-mssr.c somehow? Drivers should avoid using subsys_initcall(). Why do you use a subsys_initcall()? To avoid probe deferral in the USB susbystem? What happens if the rcar-usb2-clock-sel uses builtin_platform_driver()? Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html