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

[Damien Le Moal <damien.lemoal@opensource.wdc.com>]

On 8/30/22 18:05, Paul Menzel wrote:
> 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?

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

>> 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.


-- 
Damien Le Moal
Western Digital Research