linux-kernel - Re: [PATCH v2 3/3] ata: ahci: Skip 200 ms debounce delay for AMD 300 Series Chipset SATA Controller

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Message-ID: <178704d0-b5fd-f750-b77e-fece6c6d81dd@molgen.mpg.de>
Date:   Tue, 13 Sep 2022 17:23:15 +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,


Am 01.09.22 um 00:13 schrieb Damien Le Moal:
> On 8/30/22 18:05, Paul Menzel wrote:

[…]

>> 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?
> 
> No progress. I need to put together a series with all the patches that
> were sent already. Unless Mario can resend something ?

No reply from Mario.

>>> 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.
> 
> Let's see were the lpm stuff goes first.

It shouldn’t be too much hassle to adapt the lpm series after the patch 
is applied.


Kind regards,

Paul