From: b-cousson@ti•com (Cousson, Benoit)
To: linux-arm-kernel@lists•infradead.org
Subject: [RFC PATCH 06/10] hwspinlock: OMAP4: Add spinlock support in DT
Date: Thu, 8 Sep 2011 09:14:57 +0200 [thread overview]
Message-ID: <4E686B71.2060107@ti.com> (raw)
In-Reply-To: <CAK=WgbYX50R_MCgwdzywgrAEDJkmDSmeSSCuuqst5UBYk_sYow@mail.gmail.com>
Hi Ohad,
On 9/7/2011 9:58 PM, Ohad Ben-Cohen wrote:
> On Wed, Aug 24, 2011 at 4:09 PM, Benoit Cousson<b-cousson@ti•com> wrote:
>> Add a device-tree node for the spinlock.
>> Remove the static device build code if CONFIG_OF
>> is set.
>> Update the hwspinlock driver to use the of_match method.
>> Add the information in Documentation/devicetree.
>>
>> Signed-off-by: Benoit Cousson<b-cousson@ti•com>
>> Cc: Grant Likely<grant.likely@secretlab•ca>
>> Cc: Ohad Ben-Cohen<ohad@wizery•com>
>> ---
> ...
>> + spinlock {
>> + compatible = "ti,omap-spinlock";
>> + hwmods = "spinlock";
>> + };
>
> This seem to satisfy the current hwspinlock driver, but I'm wondering
> about an issue which was discussed awhile ago by Arnd and Mathieu:
>
> Hwspinlock devices provide system-wide hardware locks that are used by
> remote processors that have no other way to achieve synchronization.
>
> For that to work, each physical lock must have a system-wide unique id
> number that all processors are familiar with, otherwise they can't
> possibly assume they're using the same hardware lock.
>
> Usually SoC have a single hwspinlock device, which provides several
> hardware spinlocks, and in this case, the locks can be trivially
> numbered 0 to (num-of-locks - 1).
>
> In case boards have several hwspinlocks devices (each of which
> providing numerous hardware spinlocks) a different base id should be
> used for each hwspinlock device (they can't all use 0 as a starting
> id!).
>
> While this is certainly not common, it's just plain wrong for the
> hwspinlock driver to silently use 0 as a base id whenever it is probed
> with a device (and by that implicitly assume there will always be only
> one device).
Hehe, I'm not the one who wrote that driver :-)
This is not wrong for the current HW. The point is do we want to
anticipate potential HW evolution that might never happen on that IP?
> So we need to couple an hwspinlock device with a base id (which is
> trivially zero when there's only a single hwspinlock device). This can
> be easily achieved today using platform data, which boards will use to
> set a different base id for each of the hwspinlock devices they have
> (i'll send a patch demonstrating this soon), but I'm wondering how to
> specify this hwspinlock-specific data with DT: is there an existing
> binding we can use for this ? or should we create something like a
> "baseid" one especially for the hwspinlock driver ?
This is no different than the multiple GPIO controllers we have today.
Since we cannot rely on the DT nodes order, I added an explicit "id"
attribute to provide that information to the driver. And then the baseid
is "id * #gpios".
>> +#if defined(CONFIG_OF)
>> +static const struct of_device_id spinlock_match[] = {
>> + {.compatible = "ti,omap-spinlock", },
>> + {},
>> +}
>
> you're missing a semicolon there (yeah I actually tried to build this ;)
That was a test :-)
In fact it looks like this driver is not built with a default
omap2plus_defconfig :-(
I'll fix that.
Thanks for the review,
Benoit
next prev parent reply other threads:[~2011-09-08 7:14 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-24 13:09 [RFC PATCH 00/10] OMAP: Add DT support for early init OMAP4 devices Benoit Cousson
2011-08-24 13:09 ` [RFC PATCH 01/10] OMAP2+: l3-noc: Add support for device-tree Benoit Cousson
2011-09-08 18:01 ` Grant Likely
2011-09-08 21:59 ` Cousson, Benoit
2011-09-08 23:35 ` Grant Likely
2011-08-24 13:09 ` [RFC PATCH 02/10] arm/dts: OMAP4: Add a main ocp entry bound to l3-noc driver Benoit Cousson
2011-09-08 18:03 ` Grant Likely
2011-09-09 0:10 ` Cousson, Benoit
2011-09-09 2:41 ` Grant Likely
2011-08-24 13:09 ` [RFC PATCH 03/10] documentation/dt: Add l3-noc bindings Benoit Cousson
2011-09-08 18:06 ` Grant Likely
2011-09-09 0:18 ` Cousson, Benoit
2011-08-24 13:09 ` [RFC PATCH 04/10] arm/dts: OMAP4: Add mpu, dsp and iva nodes Benoit Cousson
2011-09-08 18:07 ` Grant Likely
2011-08-24 13:09 ` [RFC PATCH 05/10] documentation/dt: Add mpu, dsp and iva bindings Benoit Cousson
2011-09-08 18:09 ` Grant Likely
2011-09-09 0:30 ` Cousson, Benoit
2011-09-09 2:40 ` Grant Likely
2011-08-24 13:09 ` [RFC PATCH 06/10] hwspinlock: OMAP4: Add spinlock support in DT Benoit Cousson
2011-09-07 19:58 ` Ohad Ben-Cohen
2011-09-08 7:14 ` Cousson, Benoit [this message]
2011-09-08 7:56 ` Ohad Ben-Cohen
2011-09-08 8:07 ` Cousson, Benoit
2011-09-08 8:11 ` Ohad Ben-Cohen
2011-09-08 14:47 ` Arnd Bergmann
2011-09-08 15:34 ` Cousson, Benoit
2011-09-08 16:03 ` Arnd Bergmann
2011-09-08 16:36 ` Ohad Ben-Cohen
2011-09-09 12:58 ` Arnd Bergmann
2011-09-11 7:57 ` Ohad Ben-Cohen
2011-09-12 14:32 ` Arnd Bergmann
2011-08-24 13:09 ` [RFC PATCH 07/10] documentation/dt: Add spinlock bindings Benoit Cousson
2011-09-08 18:10 ` Grant Likely
2011-09-09 0:32 ` Cousson, Benoit
2011-08-24 13:09 ` [RFC PATCH 08/10] gpio/omap: Adapt GPIO driver to DT Benoit Cousson
2011-09-08 18:15 ` Grant Likely
2011-09-09 1:48 ` Cousson, Benoit
2011-08-24 13:09 ` [RFC PATCH 09/10] arm/dts: OMAP4: Add gpio nodes Benoit Cousson
2011-09-08 18:16 ` Grant Likely
2011-08-24 13:09 ` [RFC PATCH 10/10] documentation/dt: Add OMAP GPIO properties Benoit Cousson
2011-09-08 18:18 ` Grant Likely
2011-09-09 1:51 ` Cousson, Benoit
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