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

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Message-Id: <F363B498-5648-4C19-BC16-096EE12C29CE@codeaurora.org>
Date:	Wed, 4 Sep 2013 12:51:11 -0500
From:	Kumar Gala <galak@...eaurora.org>
To:	Suman Anna <s-anna@...com>
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


On Sep 4, 2013, at 12:03 PM, Suman Anna wrote:

>>>>>>>> 
>>>>>>>>> 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.


It would be something simple like:

static inline int of_get_hwlock_base_id (struct device_node *dn) {
#ifdef CONFIG_OF
	u32 val;

	if (of_property_read_u32(dn, "hwlock-base-id", &val)
		return val;
#endif
	return 0;
}

make sense?

- k

-- 
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation

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