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

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Message-ID: <522767E5.9080302@ti.com>
Date:	Wed, 4 Sep 2013 12:03:33 -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

>>>>>>>
>>>>>>>> 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.
> 
> I'm good with that, cell-index is always funny so might as well be explicit.
> 
> I'm also good with hwlock-num-locks, I'll update the msm spinlock driver to use this.
> 
> Can you also maybe add some helper functions into the hwspinlock core to return these values so we both don't duplicate code in drivers and maintain consistency.

I am trying to understand what you would need these for. Your driver
would already know the base_id and num_locks, since these are used in
the registration function.

regards
Suman
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