From: valentine.barshak@cogentembedded•com (Valentine)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH V2] media: i2c: Add ADV761X support
Date: Fri, 29 Nov 2013 16:14:39 +0400 [thread overview]
Message-ID: <5298852F.6030303@cogentembedded.com> (raw)
In-Reply-To: <52987058.80700@metafoo.de>
On 11/29/2013 02:45 PM, Lars-Peter Clausen wrote:
> On 11/29/2013 11:37 AM, Linus Walleij wrote:
>> On Wed, Nov 27, 2013 at 5:40 PM, Laurent Pinchart
>> <laurent.pinchart@ideasonboard•com> wrote:
>>> (CC'ing Linus Walleij, Wolfram Sang and LAKML)
>>> On Wednesday 27 November 2013 16:32:01 Valentine wrote:
>>>> On 11/27/2013 04:14 PM, Hans Verkuil wrote:
>>
>>>>> Yes, of course. Although the adv7604 has two interrupt lines, so if you
>>>>> would want to use the second, then that would still have to be specified
>>>>> through the platform data.
>>>>
>>>> In this case the GPIO should be configured as interrupt source in the
>>>> platform code. But this doesn't seem to work with R-Car GPIO since it is
>>>> initialized later, and the gpio_to_irq function returns an error.
>>>> The simplest way seemed to use a GPIO number in the platform data
>>>> to have the adv driver configure the pin and request the IRQ.
>>>> I'm not sure how to easily defer I2C board info IRQ setup (and
>>>> camera/subdevice probing) until GPIO driver is ready.
>>>
>>> Good question. This looks like a core problem to me, not specific to the
>>> adv761x driver. Linus, Wolfram, do you have a comment on that ?
>>
>> So we recently has a large-ish discussion involving me, Stephen
>> Warren and Jean-Christophe, leading to the conclusion that the
>> gpio_chip and irq_chip abstractions are orthogonal, and you should
>> be able to request a GPIO or IRQ without interacting with the other
>> subsystem.
>>
>> Specifically you should be able to request an IRQ from the irq_chip
>> portions of the driver without first requesting the GPIO line.
>>
>> Some drivers already support this.
>>
>> We added an internal API to the gpiolib so that the lib, *internally*
>> can be made aware that a certain GPIO line is used for IRQs,
>> see commit d468bf9ecaabd3bf3a6134e5a369ced82b1d1ca1
>> "gpio: add API to be strict about GPIO IRQ usage"
>>
>> So I guess the answer to the question is something like, fix
>> the GPIO driver to stop requiring the GPIO lines to be requested
>> and configured before being used as IRQs, delete that code,
>> and while you're at it add a call to gpiod_lock_as_irq()
>> to your GPIO driver in the right spot: examples are on the
>> mailing list and my mark-irqs branch in the GPIO tree.
>
> As far as I understand it this already works more or less with the driver.
> The problem is that the IRQ numbers are dynamically allocated, while the
> GPIO numbers apparently are not. So the board code knows the the GPIO number
> at compile time and can pass this to the diver which then does a gpio_to_irq
> to lookup the IRQ number.
This is correct.
> This of course isn't really a problem with
> devicetree, but only with platform board code.
I'm not sure what's the difference here and why it is not a problem with devicetree?
The other problem with R-Car GPIO driver is that it apparently does not support level IRQs.
>
> - Lars
>
Thanks,
Val.
next prev parent reply other threads:[~2013-11-29 12:14 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1384520071-16463-1-git-send-email-valentine.barshak@cogentembedded.com>
[not found] ` <5295E231.9030200@cisco.com>
[not found] ` <5295E641.6060603@cogentembedded.com>
2013-11-27 16:40 ` [PATCH V2] media: i2c: Add ADV761X support Laurent Pinchart
2013-11-27 16:48 ` Lars-Peter Clausen
2013-11-29 10:37 ` Linus Walleij
2013-11-29 10:45 ` Lars-Peter Clausen
2013-11-29 12:14 ` Valentine [this message]
2013-11-29 13:46 ` Linus Walleij
2013-11-29 13:42 ` Linus Walleij
2013-11-29 13:48 ` Lars-Peter Clausen
2013-11-29 19:52 ` Linus Walleij
2013-11-29 20:03 ` Laurent Pinchart
2013-11-29 20:05 ` Lars-Peter Clausen
2013-11-29 20:09 ` Linus Walleij
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5298852F.6030303@cogentembedded.com \
--to=valentine.barshak@cogentembedded$(echo .)com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox