From: elen.song@atmel•com (Elen Song)
To: linux-arm-kernel@lists•infradead.org
Subject: [question] some question about the residue
Date: Mon, 26 Nov 2012 18:37:28 +0800 [thread overview]
Message-ID: <50B34668.1090402@atmel.com> (raw)
In-Reply-To: <20121126102200.GB19440@n2100.arm.linux.org.uk>
On 2012-11-26 18:22, Russell King - ARM Linux wrote:
> On Mon, Nov 26, 2012 at 03:35:42PM +0800, Elen Song wrote:
>> On 2012-11-26 14:49, Vinod Koul wrote:
>>> On Mon, 2012-11-26 at 14:43 +0800, Elen Song wrote:
>>>> Hi All:
>>>>
>>>> I got a question about the residue in struct dma_tx_state:
>>>>
>>>> I wonder what residue means, is it the current descriptor residue or
>>>>
>>>> the total dma buffer residue?
>>> You read the status for descriptor, so it means this is residue for said
>>> descriptor.
>>>
>>>
>> Hi Koul:
>>
>> Well , I don't get it , if I read the status of a LLI, is it means the
>> residue of total LLI length?
>>
>> I saw driver/dma/amba-pl08x.c drivers/dma/coh901318.c, if read status of
>> a LLI, residue is the remain of LLI, not only
>> current descriptor.
>>
>> 1 patch from Russel King how he realize device_tx_status said:
>>
>> [PATCH] ARM: PL08x: clean up LLI lookup
>> As the LLI list is an array, we can use maths to locate which LLI
>> index we're currently at, and then sum up the remaining LLI entries
>> until we reach the end of the list.
>>
>> Is it right?
> It is as far as fixing a pretty major bug in the driver, but it doesn't
> fix the other bug in the driver where it sums up all outstanding
> descriptors, which pre-dates the understanding of 'residue'.
So residue actually means current active descriptor remain, it should
not sums up all outstanding descriptors.
the way amba-p108x.c and coh901318.c is wrong , right?
best regards
next prev parent reply other threads:[~2012-11-26 10:37 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-26 6:43 [question] some question about the residue Elen Song
2012-11-26 6:49 ` Vinod Koul
2012-11-26 7:35 ` Elen Song
2012-11-26 10:22 ` Russell King - ARM Linux
2012-11-26 10:37 ` Elen Song [this message]
2012-11-26 10:40 ` Russell King - ARM Linux
2012-11-27 2:39 ` Elen Song
2012-11-26 10:19 ` Russell King - ARM Linux
-- strict thread matches above, loose matches on Subject: below --
2012-11-26 3:19 Elen Song
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