From: swarren@wwwdotorg•org (Stephen Warren)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v7 05/11] ARM: dts: enable hi4511 with device tree
Date: Wed, 28 Aug 2013 08:20:18 -0600 [thread overview]
Message-ID: <521E0722.9040206@wwwdotorg.org> (raw)
In-Reply-To: <CAD6h2NSdk0fs-Z=Es9bOkwUEaubDTmAjv3hLDkrS3m1yshrbtQ@mail.gmail.com>
On 08/27/2013 08:17 PM, Haojian Zhuang wrote:
> On 27 August 2013 00:48, Stephen Warren <swarren@wwwdotorg•org> wrote:
>> On 08/23/2013 09:52 PM, Haojian Zhuang wrote:
>>> On 23 August 2013 02:50, Stephen Warren <swarren@wwwdotorg•org> wrote:
>>>> On 08/22/2013 12:07 PM, Kevin Hilman wrote:
>>>>> [+ DT maintainers]
>>>>>
>>>>> Haojian Zhuang <haojian.zhuang@linaro•org> writes:
>>>>>
>>>>>> Enable Hisilicon Hi4511 development platform with device tree support.
>>>>>>
>>>>>> Signed-off-by: Haojian Zhuang <haojian.zhuang@linaro•org>
>>>> ...
>>
>>>>>> + osc32k: osc32k {
>>>>>> + compatible = "fixed-clock";
>>>>>> + #clock-cells = <0>;
>>>>>> + clock-frequency = <32768>;
>>>>>> + clock-output-names = "osc32khz";
>>>>>> + };
>>>>>
>>>>> ...seems many of the recent users of clocks have grouped them into a
>>>>> clocks {} grouping on a "simple-bus".
>>>>>
>>>>> DT folks: is there a rule of thumb on how whether these fixed clocks
>>>>> should be grouped on a simple bus?
>>>>
>>>> I would expect all the clock node names to be just "clock", since the
>>>> node names should describe the type of device not their identity (i.e.
>>>> clock name).
>>>>
>>>> In turn, this means that each clock node name needs to use a unit
>>>> address ("@nnn") to make them unique. In turn, this means they must have
>>>> a reg property since the unit address must match the first entry in the
>>>> reg property.
>>>
>>> No, it's really bad on using a unit address. The register always contains
>>> multiple mux or gate or divider. It would cause duplicated unit address.
>>
>> There shouldn't be multiple nodes with identical reg values; if that's
>> happening, then it seems like the mapping of nodes to HW is incorrect.
>>
>> Each HW block should have 1 DT node. That way, the reg values won't collide.
>
> At here, I emphasize each clock node is one clock node. They are organized in
> tree. The same register integrates multiple clock gate/clock mux/clock divider.
> If each clock node is depend on reg, maybe it's not easy to read and the clock
> driver will be more complex.
If there's a single HW block (or single register) that provides multiple
clocks, there should be a single DT node and a single device that
provides multiple clocks.
>>> I tried to use index number also. And it's also bad to append new clock nodes.
>>> So I use the label name instead.
>>>
>>>> Now I assume these clocks don't have any memory-mapped IO registers, so
>>>> they would need an arbitrary reg value rather than a real one. So it
>>>> doesn't make sense to place them directly under the root DT node, since
>>>> their reg values would make no sense within the context of the
>>>> CPU-visible MMIO space that the root node describes.
>>>>
>>>> In this case, it's typical to put all the clock nodes into e.g. a
>>>> /clocks node, since that node can introduce a separate numbering-space
>>>> for clocks. For example, I'd expect something like:
>>>>
>>>> clocks {
>>>> #address-cells = <1>;
>>>> #size-cells = <0>;
>>>>
>>>> osc32k: clock at 0 {
>>>> compatible = "fixed-clock";
>>>> reg = <0>;
>> ...
>>>> osc26m: clock at 1 {
>>>> compatible = "fixed-clock";
>>>> reg = <1>;
>> ...
>>
>>> Those fixed-clock doesn't contain reg property. Since it needs not to access
>>> any clock register. It only provides the clock rate those child clock node.
>>
>> Inside the clocks node, the reg property is just a dummy value.
>
> Is a dummy value helpful? I don't think so.
It's not a matter of whether it's helpful; it's just how DT works.
next prev parent reply other threads:[~2013-08-28 14:20 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-20 2:31 [PATCH v7 00/11] Enable Hisilicon Hi3620 SoC Haojian Zhuang
2013-08-20 2:31 ` [PATCH v7 01/11] ARM: debug: support debug ll on hisilicon soc Haojian Zhuang
2013-08-20 2:31 ` [PATCH v7 02/11] clk: hi3xxx: add clock support Haojian Zhuang
2013-08-21 21:29 ` Mike Turquette
2013-08-24 4:13 ` Haojian Zhuang
2013-08-20 2:31 ` [PATCH v7 03/11] clk: gate: add CLK_GATE_SEPERATED_REG flag Haojian Zhuang
2013-08-21 21:18 ` Mike Turquette
2013-08-20 2:31 ` [PATCH v7 04/11] ARM: hi3xxx: add board support with device tree Haojian Zhuang
2013-08-20 2:31 ` [PATCH v7 05/11] ARM: dts: enable hi4511 " Haojian Zhuang
2013-08-22 18:07 ` Kevin Hilman
2013-08-22 18:50 ` Stephen Warren
2013-08-24 3:52 ` Haojian Zhuang
2013-08-26 16:48 ` Stephen Warren
2013-08-28 2:17 ` Haojian Zhuang
2013-08-28 14:20 ` Stephen Warren [this message]
2013-08-28 15:15 ` Haojian Zhuang
2013-08-28 15:45 ` Stephen Warren
2013-08-24 3:59 ` Haojian Zhuang
2013-08-20 2:31 ` [PATCH v7 06/11] ARM: config: enable hi3xxx in multi_v7_defconfig Haojian Zhuang
2013-08-20 2:31 ` [PATCH v7 07/11] ARM: config: add defconfig for Hi3xxx Haojian Zhuang
2013-08-20 2:31 ` [PATCH v7 08/11] ARM: hi3xxx: add smp support Haojian Zhuang
2013-08-28 2:12 ` Olof Johansson
2013-08-28 11:53 ` zhangfei gao
2013-08-28 17:19 ` Olof Johansson
2013-08-29 1:54 ` zhangfei
2013-08-20 2:31 ` [PATCH v7 09/11] ARM: hi3xxx: add hotplug support Haojian Zhuang
2013-08-28 2:21 ` Olof Johansson
2013-08-28 11:45 ` zhangfei gao
2013-08-20 2:31 ` [PATCH v7 10/11] ARM: hi3xxx: add clk-hi3716 Haojian Zhuang
2013-08-21 21:43 ` Mike Turquette
2013-08-22 1:19 ` zhangfei gao
2013-08-22 5:59 ` Mike Turquette
2013-08-22 7:50 ` Haojian Zhuang
2013-08-22 8:16 ` Mike Turquette
2013-08-20 2:31 ` [PATCH v7 11/11] ARM: hi3xxx: support hi3716-dkb board Haojian Zhuang
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