linux-kernel - Re: [PATCH] DTS: DMA: Fix DMA3 interrupts

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Date:	Thu, 12 Dec 2013 17:46:14 +0800
From:	Hongbo Zhang <hongbo.zhang@...escale.com>
To:	Scott Wood <scottwood@...escale.com>
CC:	<benh@...nel.crashing.org>, <linuxppc-dev@...ts.ozlabs.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] DTS: DMA: Fix DMA3 interrupts


On 12/11/2013 02:33 AM, Scott Wood wrote:
> On Tue, 2013-12-10 at 18:33 +0800, Hongbo Zhang wrote:
>> Scott,
>> This issue is due to the non-continuous MPIC register, I think there is
>> two ways to fix it.
>>
>> The first one is as what we are discussing, in fact the Bman/Qman DT
>> author had introduced this way, and I had to follow it, it is a trick,
>> adding 208 is a bit ugly I think, and even difficult to explain it to
>> customers etc, but this way changes less codes.
>>
>> The second one is editing MPIC related codes without adding 208 to high
>> interrupts. The point of translate interrupt number to MPIC register
>> address is a so called 'isu' mechanism, we can do like the following
>> example codes, then the tricky adding 208 isn't needed any more.
>>
>> Which one do you prefer?
>> In fact I myself prefer the second, if the idea is acceptable, I will
>> send a patch instead of this one. (and also alone with the internal
>> patch decreasing 208 for the Bman/Qman)
>>
>> void __init corenet_ds_pic_init(void)
>> {
>>       ......
>>
>>       mpic = mpic_alloc(NULL, 0, flags, 0, 512, "OpenPIC");
>>       BUG_ON(mpic == NULL);
>>
>> // Add this start
>>       for (i = 0; i < 17; i++) {
>>           if (i < 11)
>>               addr_off = 0x10000 + 0x20 * 16 * i;
>>           else
>>               addr_off = 0x13000 + 0x20 * 16 * (i - 11);  /* scape the
>> address not for interrupts */
>>           mpic_assign_isu(mpic, i, mpic->paddr + addr_off);
>>       }
>> // Add this end
>>
>>       mpic_init(mpic);
>> }
> NACK
>
> We already have a binding that states that the interrupt number is based
> on the register offset, rather than whatever arbitrary numbers hardware
> documenters decide to use next week.
>
> While I'm not terribly happy with the usability of this, especially now
> that it's not a simple "add 16", redefining the existing binding is not
> OK (and in any case the code above seems obfuscatory).  If we decide to
> do something other than continue with register offset divided by 32,
> then we need to define a new interrupt type (similar to current defined
> types of error interrupt, timer, and IPI) for the new numberspace -- and
> it should be handled when decoding that type of interrupt specifier,
> rather than with the isu mechanism.
>
> -Scott
>
>
Scott,
Thanks for your comments. Since the second way isn't so good, let's 
choose the original one.
But we meet a small accident now.
My patch is based on the http://patchwork.ozlabs.org/patch/291553/, 
which had been superseded, so this thread can be closed now.

And Shenzhou has already sent a complete dma3 dtsi patch including 
correct interrupt numbers, http://patchwork.ozlabs.org/patch/300026/, so 
let's focus on this patch, and I will forward your first comments of my 
patch there.

Thanks.



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