linux-kernel - Re: [PATCH 1/2] hwspinlock/omap: add support for dt nodes

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Message-ID: <52275F7D.4030305@ti.com>
Date:	Wed, 4 Sep 2013 11:27:41 -0500
From:	Suman Anna <s-anna@...com>
To:	Kumar Gala <galak@...eaurora.org>
CC:	Ohad Ben-Cohen <ohad@...ery.com>, Tony Lindgren <tony@...mide.com>,
	Benoit Cousson <bcousson@...libre.com>,
	<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	<devicetree@...r.kernel.org>
Subject: Re: [PATCH 1/2] hwspinlock/omap: add support for dt nodes

Kumar,

>>>>>
>>>>>> HwSpinlock IP is present only on OMAP4 and other newer SoCs,
>>>>>> which are all device-tree boot only. This patch adds the
>>>>>> base support for parsing the DT nodes, and removes the code
>>>>>> dealing with the traditional platform device instantiation.
>>>>>>
>>>>>> Signed-off-by: Suman Anna <s-anna@...com>
>>>>>> ---
>>>>>> .../devicetree/bindings/hwlock/omap-hwspinlock.txt | 28 ++++++++++
>>>>>> arch/arm/mach-omap2/Makefile                       |  3 --
>>>>>> arch/arm/mach-omap2/hwspinlock.c                   | 60 ----------------------
>>>>>> drivers/hwspinlock/omap_hwspinlock.c               | 21 ++++++--
>>>>>> 4 files changed, 45 insertions(+), 67 deletions(-)
>>>>>> create mode 100644 Documentation/devicetree/bindings/hwlock/omap-hwspinlock.txt
>>>>>> delete mode 100644 arch/arm/mach-omap2/hwspinlock.c
>>>>>>
>>>>>> diff --git a/Documentation/devicetree/bindings/hwlock/omap-hwspinlock.txt b/Documentation/devicetree/bindings/hwlock/omap-hwspinlock.txt
>>>>>> new file mode 100644
>>>>>> index 0000000..adfb8ad
>>>>>> --- /dev/null
>>>>>> +++ b/Documentation/devicetree/bindings/hwlock/omap-hwspinlock.txt
>>>>>> @@ -0,0 +1,28 @@
>>>>>> +OMAP4+ HwSpinlock Driver
>>>>>> +
>>>>>> +Required properties:
>>>>>> +- compatible:		Currently supports only "ti,omap4-hwspinlock" for
>>>>>> +				OMAP44xx, OMAP54xx, AM33xx, AM43xx, DRA7xx SoCs
>>>>>> +- reg:			Contains the hwspinlock register address range (base
>>>>>> +			address and length)
>>>>>> +- ti,hwmods:		Name of the hwmod associated with the hwspinlock device
>>>>>> +
>>>>>> +Optional properties:
>>>>>> +- base_id:		Base Id for the locks for a particular hwspinlock
>>>>>> +			device. If not mentioned, a default value of 0 is used.
>>>>>> +			This property is mandatory ONLY if a SoC has several
>>>>>> +			hwspinlock devices. There are currently no such OMAP
>>>>>> +			SoCs.
>>>>>
>>>>> Should this be ti,base_id ? [ I know its kinda generic in its intent for any SoC w/multiple blocks ]
>>>>
>>>> I didn't add the "ti," prefix exactly for the same reason - it is
>>>> generic w.r.t the hwspinlock core irrespective of the SoC family, and
>>>> there is nothing ti or OMAP specific about it. I have added it to keep
>>>> the DT node definition in sync with the driver code. If it is too
>>>> generic a name, it can always be renamed as hwlock_base_id. This will be
>>>> SoC agnostic property for the hwspinlock driver. What do you think?
>>>
>>> I'm wondering if we should use cell-index for this purpose.
>>
>> I didn't get you completely. Do you intend to compute the base_id using
>> cell-index and number of locks (which may be a separate field altogether
>> if this information cannot be read from the h/w)? My understanding is
>> that cell-index is primarily used for identifying the h/w instance number.
> 
> I was suggesting using cell-index instead of base_id.  What we should probably due is have a devicetree/bindings/hwlock/hwlock.txt that would describe generic properties like this and just reference that in the omap binding spec.

Common hwlock.txt sounds good. Will make the change.

> 
> I'm thinking if we dont use cell-index, that it should probably be hwlock-base-id
> 

I prefer to use hwlock-base-id. I think we should also be defining a
common property name for number of locks, say hwlock-num-locks.

regards
Suman

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