Message-ID: <85f8c8cb-b4b9-b3ed-e79f-a1a161c9b672@opensource.wdc.com>
Date:   Fri, 1 Apr 2022 16:23:31 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Paul Menzel <pmenzel@...gen.mpg.de>
Cc:     Mario Limonciello <Mario.Limonciello@....com>,
        Hans de Goede <hdegoede@...hat.com>,
        linux-ide@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Nehal-bakulchandra Shah <Nehal-bakulchandra.Shah@....com>
Subject: Re: [PATCH v2 3/3] ata: ahci: Skip 200 ms debounce delay for AMD 300
 Series Chipset SATA Controller

On 4/1/22 14:18, Paul Menzel wrote:
> Dear Damien,
> 
> 
> Thank you for your reply.
> 
> 
> Am 01.04.22 um 01:04 schrieb Damien Le Moal:
>> On 3/31/22 23:42, Paul Menzel wrote:
> 
>>> Am 23.03.22 um 09:36 schrieb Paul Menzel:
>>>
>>>> Am 23.03.22 um 09:24 schrieb Damien Le Moal:
>>>>> On 3/23/22 15:55, Paul Menzel wrote:
>>>>
>>>>>> Am 23.03.22 um 06:01 schrieb Damien Le Moal:
>>>>>>> On 3/22/22 06:51, Limonciello, Mario wrote:
>>>>
>>>>>>>>> -----Original Message-----
>>>>>>>>> From: Paul Menzel <pmenzel@...gen.mpg.de>
>>>>>>>>> Sent: Monday, March 21, 2022 16:25
>>>>>>
>>>>>> […]
>>>>>>
>>>>>>>> I seem to recall that we were talking about trying to drop the
>>>>>>>> debounce delay for everything, weren't we?
>>>>>>>>
>>>>>>>> So perhaps it would be right to add a 4th patch in the series to do
>>>>>>>> just that.  Then If this turns out to be problematic for
>>>>>>>> anything other than the controllers in the series that you
>>>>>>>> identified as not problematic then that 4th patch can
>>>>>>>> potentially be reverted alone?
>>>>>>>
>>>>>>> Not quite everything :) But you are right, let's try to switch the
>>>>>>> default to no delay. I will be posting patches today for that.
>>>>>>> With these patches, your patches are not necessary anymore as the AMD
>>>>>>> chipset falls under the default no-delay.
>>>>>>
>>>>>> I am all for improving the situation for all devices, but I am unable to
>>>>>> judge the regression potential of changing this, as it affects a lot of
>>>>>> devices. I guess it’d would go through the next tree, and hopefully the
>>>>>> company QA teams can give it a good spin. I hoped that my patches, as I
>>>>>> have tested them, and AMD will hopefully too, could go into the current
>>>>>> merge window.
>>>>>
>>>>> Yes, correct, the plan is to get the generic series queued as soon
>>>>> as rc1 so that it can spend plenty of time in linux-next for people
>>>>> to test. That will hopefully reduce the risk of breaking things in
>>>>> the field. Same for  the default LPM change.
>>>>
>>>> But 5.18 or 5.19? If 5.18, sounds good to me, if 5.19, I’d be great if
>>>> my patches go into 5.18 cycle, as they have been tested, and it would
>>>> mean the whole change gets tested more widely already.
>>>>
>>>>> With the default removal of the debounce delay, your patches addressing
>>>>> only the AMD adapter are not needed anymore: this adapter will not have a
>>>>> debounce delay unless the ATA_LFLAG_DEBOUNCE_DELAY flag is set.
>>>>
>>>> Yes, I understand.
>>>
>>> The merge window for Linux 5.18 is going to close in three days this
>>> Sunday. It’d be really great if my patches, tested on hardware, could go
>>> into that.
>>>
>>>>>>> It would be nice if you can test though.
>>>>>>
>>>>>> Of course, I am going to that either way.
>>>>>
>>>>> Series posted with you on CC. Please test !
>>>>
>>>> Thank you. I am going to test it in the coming days, and report back.
>>>>
>>>> Maybe more people should be put in Cc (Dell, Lenovo, IBM, x86 subsystem)
>>>> with a request to test this?
>>> Thank you for the patches, which are a big improvement. Let’s hope, you
>>> can re-roll them, so they get into Linux very soon for everyone’s benefit.
>>
>> I am waiting for 5.18-rc1 to rebase the patches and re-post them. Given
>> reviewed-by and tested-by tags, I will queue them for 5.19.
> 
> As discussed in the other thread, it’s impossible to be 100 % certain, 
> it won’t break anything.

Yes, that is why I want to push the patches early in the cycle to be able
to revert if too many problems are reported.

> 
>> 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.
> 
> 
> Kind regards,
> 
> Paul


-- 
Damien Le Moal
Western Digital Research

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