From: santosh.shilimkar@ti•com (Santosh Shilimkar)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 1/3] misc: Add crossbar driver
Date: Thu, 15 Aug 2013 17:14:45 -0400 [thread overview]
Message-ID: <520D44C5.6080205@ti.com> (raw)
In-Reply-To: <CACRpkdYeo1y-HhftkRWgwyq8o-NVuJ978Uq+ON880LHhUxC=hg@mail.gmail.com>
On Thursday 15 August 2013 04:51 PM, Linus Walleij wrote:
> On Thu, Aug 15, 2013 at 10:26 PM, Santosh Shilimkar
> <santosh.shilimkar@ti•com> wrote:
>> On Thursday 15 August 2013 04:01 PM, Linus Walleij wrote:
>>> On Tue, Aug 13, 2013 at 11:56 AM, Sricharan R <r.sricharan@ti•com> wrote:
>>>
>>>> Initially irqchip was discussed, but we also have a DMA crossbar
>>>> to map the dma-requests. Since both irq/dma crossbars should be handled,
>>>> pinctrl was suggested as the appropriate place to handle this.
>>>
>>> I think it is better to use irqchip.
>>>
>> Did you happen to read the thread why irqchip is in-appropriate
>> for such an IP.
>
> Sorry I don't understand what thread that is... can you point me there?
> My previous statement on this issue what this:
> http://marc.info/?l=linux-kernel&m=137442541628641&w=2
>
It was discussed in couple of threads but the main point was the
need of a link needed for the irqchip.
>> As I said earlier, an IRQ-chip always need a
>> real IRQ link (even for the chained one) to the primary irqchip.
>>
>> This IP is just dummy IP makes the connections for the primary
>> irqchip(read GIC). And its use only limited to make the
>> connection between the peripheral IRQ event to the GIC IRQ line.
>>
>> I don't see how you can make this happen with an irqchip
>> infrastructure.
>
> I think my post above describes this.
>
Sorry for being dumb but I don't think cascaded irqchip examples
like GPIO and cross-bars are same. If you take an example of
GPIO irqchip, it always have a physical connection even if it
is 1 IRQ line for (32 logical/sparse IRQs). That goes with
other MFD examples too.
So may be I am still missing something in your proposal.
>>> I don't see any way to really abstract this pretty simple crossbar
>>> for reuse across subsystems.
>>>
>> This exactly the reason, i am against idea of over-engineering the
>> simple IP whose only job is to make the physical wire connection
>> in software where as this is generally done in RTL by default on
>> most of the SOCs.
>
> Well, it was made accessible by software, and if someone has a
> usecase that requires this do be done dynamically, i.e. not just
> being set up by firmware and never touched, and that use case
> is valid, then I guess we need to do something...
>
> I think it was mentioned in the thread that there is really such
> a usecase?
>
Actually there is no practical usecase but one but one can manufacture
it ;-)
next prev parent reply other threads:[~2013-08-15 21:14 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-18 16:43 [PATCH 0/3] Add crossbar driver Sricharan R
2013-07-18 16:43 ` [PATCH 1/3] misc: " Sricharan R
2013-07-18 16:55 ` Joe Perches
2013-07-18 18:25 ` Felipe Balbi
2013-07-21 16:33 ` Linus Walleij
2013-07-18 18:56 ` Nishanth Menon
2013-07-18 23:39 ` Santosh Shilimkar
2013-07-19 0:13 ` Nishanth Menon
2013-07-19 10:48 ` Sricharan R
2013-07-19 7:17 ` Tony Lindgren
2013-07-19 10:48 ` Sricharan R
2013-07-21 16:49 ` Linus Walleij
2013-07-22 12:20 ` Sricharan R
2013-07-22 16:23 ` Santosh Shilimkar
2013-07-24 16:08 ` Nishanth Menon
2013-07-24 16:38 ` Santosh Shilimkar
2013-07-24 16:47 ` Nishanth Menon
2013-07-24 18:43 ` Sricharan R
2013-07-24 18:51 ` Nishanth Menon
2013-07-24 18:59 ` Santosh Shilimkar
2013-08-13 8:10 ` Tony Lindgren
2013-08-13 9:56 ` Sricharan R
2013-08-13 13:29 ` Santosh Shilimkar
2013-08-15 20:01 ` Linus Walleij
2013-08-15 20:26 ` Santosh Shilimkar
2013-08-15 20:51 ` Linus Walleij
2013-08-15 21:14 ` Santosh Shilimkar [this message]
2013-08-21 21:10 ` Linus Walleij
2013-08-22 11:33 ` Sricharan R
2013-08-22 13:45 ` Santosh Shilimkar
2013-08-23 4:47 ` Rajendra Nayak
2013-08-23 6:11 ` Sricharan R
2013-08-23 6:17 ` Rajendra Nayak
2013-08-23 6:36 ` Sekhar Nori
2013-08-23 6:53 ` Sricharan R
2013-08-23 8:14 ` Sekhar Nori
2013-08-23 13:38 ` Santosh Shilimkar
2013-08-23 16:28 ` Sekhar Nori
2013-08-23 19:06 ` Linus Walleij
2013-08-23 19:44 ` Santosh Shilimkar
2013-08-13 13:28 ` Santosh Shilimkar
2013-08-14 7:27 ` Tony Lindgren
2013-07-18 16:43 ` [PATCH 2/3] ARM: dts: DRA: Add crossbar device binding Sricharan R
2013-07-18 19:04 ` Nishanth Menon
2013-07-18 16:43 ` [PATCH 3/3] ARM: DRA7xx: Enable crossbar driver for the soc Sricharan R
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