Hi Geert-san,

From: Geert Uytterhoeven
Sent: Wednesday, July 5, 2017 9:22 PM

Hi Shimoda-san,

On Wed, Jul 5, 2017 at 1:57 PM, Yoshihiro Shimoda
[off-list ref] wrote:

quoted

quoted

From: Geert Uytterhoeven
Sent: Wednesday, July 5, 2017 7:09 PM
On Wed, Jun 28, 2017 at 8:28 AM, Yoshihiro Shimoda
[off-list ref] wrote:

quoted

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.

quoted

quoted

quoted

--- /dev/null
+++ b/drivers/clk/renesas/rcar-usb2-clock-sel.c

quoted

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+/* 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?

Best regards,
Yoshihiro Shimoda

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

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

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