Re: [PATCH 3/3] arm64: dts: rockchip: add clk-480m for ehci and ohci of rk3399

[Heiko Stuebner <heiko@sntech.de>]

Am Donnerstag, 15. Dezember 2016, 08:34:09 CET schrieb Doug Anderson:
> Hi,
> 
> On Wed, Dec 14, 2016 at 10:41 PM, Frank Wang <frank.wang@rock-chips.com> 
wrote:
> > Hi Brain, Doug and Heiko,
> > 
> > I would like to summarize why this story was constructed.
> > 
> > The ehci/ohci-platform suspend process are blocked due to UTMI clock which
> > directly output from usb-phy has been disabled, and why the UTMI clock was
> > disabled?
> > 
> > UTMI clock and 480m clock all output from the same internal PLL of
> > usb-phy,
> > and there is only one bit can use to control this PLL on or off, which we
> > named "otg_commononn"(GRF, offset 0x0e450/0x0e460 bit4 ) in RK3399 TRM.
> > 
> > When system boot up, ehci/ohci-platform probe function invoke
> > phy_power_on(), further invoke rockchip_usb2phy_power_on() to enable 480m
> > clock, actually, it sets the otg_commononn bit on, and then usb-phy will
> > go
> > to (auto)suspend if there is no devices plug-in after 1 minute, the
> > rockchip_usb2phy_power_off() will be invoked and the 480m clock may be
> > disabled in the (auto)suspend process. As a result, the otg_commononn bit
> > may be turned off, and all output clock of usb-phy will be disabled.
> > However, ehci/ohci-platform PM suspend operation (read/write controller
> > register) are based on the UTMI clock.
> > 
> > So we introduced "clk_usbphy0_480m_src"/"clk_usbphy1_480m_src" as one
> > input
> > clock for ehci/ohci-platform, in this way, the otg_commononn bit is not
> > turned off until ehci/ohci-platform go to PM suspend.
> 
> I still need to digest all of the things that were added to this
> thread overnight, but nothing I've seen so far indicates that you need
> the post-gated clock.  AKA I still think you need to redo your patch
> to replace:
> 
>               clocks = <&cru HCLK_HOST0>, <&cru HCLK_HOST0_ARB>,
>                        <&cru SCLK_USBPHY0_480M_SRC>;
> 
> with:
> 
>               clocks = <&cru HCLK_HOST0>, <&cru HCLK_HOST0_ARB>,
>                         <&u2phy0>;
> 
> Can you please comment on that?

Also, with the change, the ehci will keep the clock (and thus the phy) always 
on. Does the phy-autosuspend even save anything now?

In any case, could we make the clock-names entry sound nicer than usbphy0_480m 
please? bindings/usb/atmel-usb.txt calls its UTMI clock simply "usb_clk", but 
something like "utmi" should also work.
While at it you could also fix up the other clock names to something like 
"host" and "arbiter" or so?.


Heiko