[PATCH V2] clk: introduce u-boot,ignore-clk-defaults

[Peng Fan (OSS)]

> Subject: Re: [PATCH V2] clk: introduce u-boot,ignore-clk-defaults
> 
> On Mon, Nov 22, 2021 at 11:33:27AM +0800, Peng Fan (OSS) wrote:
> > + Rob
> >
> > On 2021/11/20 20:57, Tom Rini wrote:
> > > On Sat, Nov 20, 2021 at 12:10:54PM +0000, Peng Fan (OSS) wrote:
> > > > > Subject: [PATCH V2] clk: introduce u-boot,ignore-clk-defaults
> > > > >
> > > > > From: Peng Fan <peng.fan at nxp.com>
> > > > >
> > > > > Current code has a force clk_set_defaults in multiple stages,
> > > > > U-Boot reuse the same device tree and Linux Kernel device tree,
> > > > > but we not register all the clks as Linux Kernel, so
> > > > > clk_set_defaults will fail and cause the clk provider registeration fail.
> > > > >
> > > > > So introduce a new property to ignore the default settings which
> > > > > could be used by any node that wanna ignore default settings.
> > > > >
> > > > > Reviewed-by: Simon Glass <sjg at chromium.org>
> > > > > Signed-off-by: Peng Fan <peng.fan at nxp.com>
> > > > > ---
> > > > >
> > > > > V2:
> > > > >   Add R-b tag
> > > > >   Tom, Simon
> > > > >     After a thought, I think still put it as a u-boot thing.
> assigned-clock-x is
> > > > >     actually Linux specific, however I could not add the new property
> to Linux,
> > > > >     because we are supporting SystemReady-IR, we need the
> > > > > assigned-clock-x property
> > > > >     in linux working and ignore it in U-Boot.
> > > >
> > > > Any more thoughts?
> > >
> > > Just my continued request that you treat this as generic and submit
> > > the binding upstream so it can be in the device tree for the platform.
> > >
> >
> > As Sean said, this is to serve cast that linux and U-Boot use the same
> > device tree, I mean U-Boot runtime export device tree to linux for
> > SR-IR (system-ready IR) booting.
> >
> > Linux needs assigned-clocks to some reason, but U-Boot not need that
> > because the driver not added the support or not a must to have that.
> >
> > Because assigned-clocks failure in U-Boot will cause probe fail now,
> > the device driver will report failure.
> >
> > You mean rename this to "ignore-clk-defaults" or keep
> > "u-boot,ignore-clk-defauls" or "firmware,ignore-clk-defaults" to linux
> > device tree binding?
> >
> > I could try to send to linux kernel with "firmware" as a prefix.
> 
> What I mean is that first I'm not seeing the description of the property as
> being clear enough, either in commit message or the binding itself.
> That's why in my mind I keep seeing this as "we set the properties
> linux,assigned-clocks and u-boot,ignore-clk-defaults" and I don't know why
> we need both.  Is there not something we can do based on seeing
> linux,assigned-clocks ?  Showing something that makes use of the property
> you're wishing to add would be helpful.  In fact, some specific dts snippets
> would be helpful to understand what's going on here.

clk: clock-controller at 30380000 {
        compatible = "fsl,imx8mp-ccm";
        reg = <0x30380000 0x10000>;
        #clock-cells = <1>;
        clocks = <&osc_32k>, <&osc_24m>, <&clk_ext1>, <&clk_ext2>,
                 <&clk_ext3>, <&clk_ext4>;
        clock-names = "osc_32k", "osc_24m", "clk_ext1", "clk_ext2",
                      "clk_ext3", "clk_ext4";
        assigned-clocks = <&clk IMX8MP_CLK_A53_SRC>,
                          <&clk IMX8MP_CLK_A53_CORE>,
                          <&clk IMX8MP_CLK_NOC>,
                          <&clk IMX8MP_CLK_NOC_IO>,
                          <&clk IMX8MP_CLK_GIC>,
                          <&clk IMX8MP_CLK_AUDIO_AHB>,
                          <&clk IMX8MP_CLK_AUDIO_AXI_SRC>,
                          <&clk IMX8MP_CLK_IPG_AUDIO_ROOT>,
                          <&clk IMX8MP_AUDIO_PLL1>,
                          <&clk IMX8MP_AUDIO_PLL2>;
        assigned-clock-parents = <&clk IMX8MP_SYS_PLL1_800M>,
                                 <&clk IMX8MP_ARM_PLL_OUT>,
                                 <&clk IMX8MP_SYS_PLL2_1000M>,
                                 <&clk IMX8MP_SYS_PLL1_800M>,
                                 <&clk IMX8MP_SYS_PLL2_500M>,
                                 <&clk IMX8MP_SYS_PLL1_800M>,
                                 <&clk IMX8MP_SYS_PLL1_800M>;
        assigned-clock-rates = <0>, <0>,
                               <1000000000>,
                               <800000000>,
                               <500000000>,
                               <400000000>,
                               <800000000>,
                               <400000000>,
                               <393216000>,
                               <361267200>;
        u-boot,ignore-clk-defaults;
};

The above node is that I wanna have in U-Boot device tree.
This node is same as the one used in linux device tree except the new
property introduced here.

In i.MX U-Boot, we not support the clks here in the clk driver, but linux needs the assigned-clocks property, so I could not delete it
because U-Boot runtime export the device tree to Linux.

So add a new property here for U-Boot specific usage, if the property
is there, U-Boot ignore the assigned-clock settings for a node.

I hope this is clear and please suggest what to do next.

Thanks,
Peng.
> 
> Second, if we need a new property here then yes, it goes upstream and you
> put u-boot,has-not-clk-foo or firmware,has-not-clk-foo or whatever in the
> boards dts file.
> 
> --
> Tom