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

[Sean Anderson]

On 11/22/21 10:02 PM, Peng Fan (OSS) wrote:
>> 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.

Hm. Well perhaps we can designate a specific return code to indicate
that we have a valid clock ID but it is just unimplemented. So in your
driver you would do

ulong my_get_rate(struct clk *clk)
{
	switch (clk->id) {
	case MY_CLK:
		...
	default:
		if (clk->id < MY_CLK_MAX)
			return -ENOSYS;
		else
			return -EINVAL;
	}
}

and then the clock rate assignment would see -ENOSYS and go on its merry
way.

--Sean