linux-kernel - Re: [PATCH v2 08/13] dmaengine: at_xdmac: Move the free desc to the tail of the desc list

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Message-ID: <dee19759-df29-0e33-8c92-a770711b4246@microchip.com>
Date:   Mon, 13 Dec 2021 09:27:45 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <vkoul@...nel.org>
CC:     <Ludovic.Desroches@...rochip.com>, <richard.genoud@...il.com>,
        <gregkh@...uxfoundation.org>, <jirislaby@...nel.org>,
        <Nicolas.Ferre@...rochip.com>, <alexandre.belloni@...tlin.com>,
        <mripard@...nel.org>, <linux-arm-kernel@...ts.infradead.org>,
        <dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-serial@...r.kernel.org>
Subject: Re: [PATCH v2 08/13] dmaengine: at_xdmac: Move the free desc to the
 tail of the desc list

On 12/13/21 11:22 AM, Tudor Ambarus wrote:
> On 12/13/21 11:00 AM, Vinod Koul wrote:
>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>
>> On 13-12-21, 14:29, Vinod Koul wrote:
>>> On 13-12-21, 08:51, Tudor.Ambarus@...rochip.com wrote:
>>>> Hi, Vinod,
>>>>
>>>> On 12/13/21 10:07 AM, Vinod Koul wrote:
>>>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>>>
>>>>> On 25-11-21, 11:00, Tudor Ambarus wrote:
>>>>>> So that we don't use the same desc over and over again.
>>>>>
>>>>> Please use full para in the changelog and not a continuation of the
>>>>> patch title!
>>>>
>>>> Ok, will add a better commit description. Here and in other patches where
>>>> your comment applies.
>>>
>>> Great!
>>>
>>>>>
>>>>> and why is wrong with using same desc over and over? Any benefits of not
>>>>> doing so?
>>>>
>>>> Not wrong, but if we move the free desc to the tail of the list, then the
>>>> sequence of descriptors is more track-able in case of debug. You would
>>>> know which descriptor should come next and you could easier catch
>>>> concurrency over descriptors for example. I saw virt-dma uses
>>>> list_splice_tail_init() as well, I found it a good idea, so I thought to
>>>> follow the core driver.
>>>
>>> Okay, I would be good to add this motivation in the change log. I am
>>> sure after few you would also wonder why you did this change :)
> 
> Sure.
> 
>>
>> Also, pls submit serial patches to Greg separately. I guess he saw the
>> title and overlooked those...
> 
> I received a private message from Greg informing me that he applied the

for clarity: Greg applied just the 2 tty patches, not the entire series.

> patches to tty-next and that they will be merged during the merge window.
> So I'll drop the tty patches in v3.

v3 will follow and it will contain just the at_xdmac patches.