From: joelf@ti.com (Joel Fernandes)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 7/9] ARM: edma: Don't clear EMR of channel in edma_stop
Date: Wed, 31 Jul 2013 20:59:27 -0500 [thread overview]
Message-ID: <51F9C0FF.7030703@ti.com> (raw)
In-Reply-To: <51F8DA5C.9060503@ti.com>
On 07/31/2013 04:35 AM, Sekhar Nori wrote:
> On Wednesday 31 July 2013 10:35 AM, Joel Fernandes wrote:
>> On 07/30/2013 03:29 AM, Sekhar Nori wrote:
>>> On Monday 29 July 2013 06:59 PM, Joel Fernandes wrote:
>>>> We certainly don't want error conditions to be cleared anywhere
>>>
>>> 'anywhere' is a really loaded term.
>>>
>>>> as this will make us 'forget' about missed events. We depend on
>>>> knowing which events were missed in order to be able to reissue them.
>>>
>>>> This fixes a race condition where the EMR was being cleared
>>>> by the transfer completion interrupt handler.
>>>>
>>>> Basically, what was happening was:
>>>>
>>>> Missed event
>>>> |
>>>> |
>>>> V
>>>> SG1-SG2-SG3-Null
>>>> \
>>>> \__TC Interrupt (Almost same time as ARM is executing
>>>> TC interrupt handler, an event got missed and also forgotten
>>>> by clearing the EMR).
>>>
>>> Sorry, but I dont see how edma_stop() is coming into picture in the race
>>> you describe?
>>
>> In edma_callback function, for the case of DMA_COMPLETE (Transfer
>> completion interrupt), edma_stop() is called when all sets have been
>> processed. This had the effect of clearing the EMR.
>
> Ah, thanks. I was missing the fact that the race comes into picture only
> when using the DMA engine driver. I guess that should be mentioned
> somewhere since it is not immediately obvious.
>
> The patch looks good to me. So if you respin just this one with some
> updated explanation based on what you wrote below, I will take it.
Sure I'll do that. Also the trigger_channel patch, will you be taking
that one too? I can send these 2 in a series as they touch
arch/arm/common/edma.c
Thanks,
-Joel
>
> Thanks,
> Sekhar
>
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next prev parent reply other threads:[~2013-08-01 1:59 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-29 13:29 [PATCH 0/9] dma: edma: Support scatter-lists of any length Joel Fernandes
2013-07-29 13:29 ` [PATCH 1/9] dma: edma: Setup parameters to DMA MAX_NR_SG at a time Joel Fernandes
2013-07-29 13:29 ` [PATCH 2/9] dma: edma: Write out and handle MAX_NR_SG at a given time Joel Fernandes
2013-07-29 13:29 ` [PATCH 3/9] ARM: edma: Add function to manually trigger an EDMA channel Joel Fernandes
2013-07-30 5:18 ` Sekhar Nori
2013-07-31 4:30 ` Joel Fernandes
2013-07-31 5:23 ` Sekhar Nori
2013-07-31 5:34 ` Fernandes, Joel
2013-07-29 13:29 ` [PATCH 4/9] dma: edma: Find missed events and issue them Joel Fernandes
2013-07-30 7:05 ` Sekhar Nori
2013-07-31 4:49 ` Joel Fernandes
2013-07-31 9:18 ` Sekhar Nori
2013-08-01 2:27 ` Joel Fernandes
2013-08-01 3:43 ` Joel Fernandes
2013-08-01 4:39 ` Joel Fernandes
2013-08-01 6:13 ` Sekhar Nori
2013-08-01 20:28 ` Joel Fernandes
2013-08-01 20:48 ` Joel Fernandes
2013-08-02 13:26 ` Sekhar Nori
2013-08-02 18:15 ` Joel Fernandes
2013-08-02 23:00 ` Joel Fernandes
2013-07-29 13:29 ` [PATCH 5/9] dma: edma: Leave linked to Null slot instead of DUMMY slot Joel Fernandes
2013-07-29 13:29 ` [PATCH 6/9] dma: edma: Detect null slot errors and handle them correctly Joel Fernandes
2013-07-29 13:29 ` [PATCH 7/9] ARM: edma: Don't clear EMR of channel in edma_stop Joel Fernandes
2013-07-30 8:29 ` Sekhar Nori
2013-07-31 5:05 ` Joel Fernandes
2013-07-31 9:35 ` Sekhar Nori
2013-08-01 1:59 ` Joel Fernandes [this message]
2013-07-29 13:29 ` [PATCH 8/9] dma: edma: Link to dummy slot only for last SG list split Joel Fernandes
2013-07-29 13:29 ` [PATCH 9/9] dma: edma: remove limits on number of slots Joel Fernandes
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