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: <3d57524a-6d88-3027-d8fb-94417ae0b4f6@microchip.com>
Date:   Mon, 13 Dec 2021 09:22:01 +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 11:00 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
patches to tty-next and that they will be merged during the merge window.
So I'll drop the tty patches in v3.

Cheers,
ta