Date:   Tue, 30 Aug 2022 11:05:53 +0200
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>
Cc:     Mario Limonciello <Mario.Limonciello@....com>,
        Hans de Goede <hdegoede@...hat.com>,
        linux-ide@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] ata: ahci: Skip 200 ms debounce delay for AMD 300
 Series Chipset SATA Controller

Dear Damien,


Sorry for the late reply, and thank you for your great work.

Am 01.06.22 um 10:58 schrieb Damien Le Moal:
> On 6/1/22 01:18, Paul Menzel wrote:
>>>>> With that in mind, I am not planning to apply your previous patches
>>>>> for 5.18, as they would conflict and would only end up being churn
>>>>> since the delay removal by default will undo your changes.
>>>> Obviously, I do not agree, as this would give the a little bit more
>>>> testing already, if changing the default is a good idea. Also, if the
>>>> conflict will be hard to resolve, I happily do it (the patches could
>>>> even be reverted on top – git commits are cheap and easy to handle).
>>>
>>> The conflict is not hard to resolve. The point is that my patches changing
>>> the default to no debounce delay completely remove the changes of your
>>> patch to do the same for one or some adapters. So adding your patches now
>>> and then my patches on top does not make much sense at all.
>>>
>>> If too many problems show up and I end up reverting/removing the patches,
>>> then I will be happy to take your patches for the adapter you tested. Note
>>> that *all* the machines I have tested so far are OK without a debounce
>>> delay too. So we could add them too... And endup with a long list of
>>> adapters that use the default ahci driver without debounce delay. The goal
>>> of changing the default to no delay is to avoid that. So far, the adapters
>>> I have identified that need the delay have their own declaration, so we
>>> only need to add a flag there. Simpler change that listing up adapters
>>> that are OK without the delay.
>>>
>>>> Anyway, I wrote my piece, but you are the maintainer, so it’s your call
>>>> and I stop bothering you.
>>
>> I just wanted to inquire about the status of your changes? I do not find
>> them in your `for-5.19` branch. As they should be tested in linux-next
>> before the merge window opens, if these are not ready yet, could you
>> please apply my (tested) patches?
> 
> I could, but 5.19 now has an updated libata.force kernel parameter that
> allows one to disable the debounce delay for a particular port or for all
> ports of an adapter. See libata.force=x.y:nodbdelay for a port y of
> adapter x or libata.force=x:nodbdelay for all ports of adapter x.

This is commit 3af9ca4d341d (ata: libata-core: Improve link flags forced 
settings) [1]. Thank you, this is really useful, but easily overlooked. ;-)

> I still plan to revisit the arbitrary link debounce timers but I prefer to
> have the power management cleanup applied first. The reason is that link
> debounce depends on PHY readiness, which itself depends heavily on power
> mode transitions. My plan is to get this done during this cycle for
> release with 5.20 and then fix on top the arbitrary delays for 5.21.

Nice. Can you share the current status?

> Is the libata.force solution OK for you until we have a final more solid
> fix that can benefit most modern adapters (and not just the ones you
> identified)? If you do have a use case that needs a "nodbdelay" horkage
> due to some constraint in the field, then I will apply your patches, but
> they likely will be voided by coming changes. Let me know.

I think, applying the patch would be an improvement, as people wouldn’t 
need to update their Linux kernel command line, and I do not mind, if it 
gets reverted/dropped later.


Kind regards,

Paul


[1]: 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3af9ca4d341d2b8756fa9056ca0715915480e251

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