linux-kernel - Re: [PATCH v3 3/3] ahci: AMD A85 FCH (Hudson D4): Skip 200 ms debounce delay in `sata_link

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Message-ID: <33deca4a-abed-123c-9530-3f15740a3261@molgen.mpg.de>
Date:   Tue, 4 Jan 2022 09:49:29 +0100
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>
Cc:     linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/3] ahci: AMD A85 FCH (Hudson D4): Skip 200 ms
 debounce delay in `sata_link_resume()`

[cc: -dmitry, -guenter]

Dear Damien,


Am 04.01.22 um 09:36 schrieb Damien Le Moal:
> On 12/31/21 16:08, Paul Menzel wrote:

>> Am 31.12.21 um 01:52 schrieb Damien Le Moal:
>>> On 12/30/21 20:08, Paul Menzel wrote:
>>>>>>     	board_ahci_nomsi,
>>>>>>     	board_ahci_noncq,
>>>>>>     	board_ahci_nosntf,
>>>>>> @@ -141,6 +142,13 @@ static const struct ata_port_info ahci_port_info[] = {
>>>>>>     		.udma_mask	= ATA_UDMA6,
>>>>>>     		.port_ops	= &ahci_ops,
>>>>>>     	},
>>>>>> +	[board_ahci_nodbdelay] = {
>>>>>> +		.flags		= AHCI_FLAG_COMMON,
>>>>>> +		.link_flags	= ATA_LFLAG_NO_DB_DELAY,
>>>>>> +		.pio_mask	= ATA_PIO4,
>>>>>> +		.udma_mask	= ATA_UDMA6,
>>>>>> +		.port_ops	= &ahci_ops,
>>>>>> +	},
>>>>>>     	[board_ahci_nomsi] = {
>>>>>>     		AHCI_HFLAGS	(AHCI_HFLAG_NO_MSI),
>>>>>>     		.flags		= AHCI_FLAG_COMMON,
>>>>>> @@ -437,6 +445,7 @@ static const struct pci_device_id ahci_pci_tbl[] = {
>>>>>>     		board_ahci_al },
>>>>>>     	/* AMD */
>>>>>>     	{ PCI_VDEVICE(AMD, PCI_DEVICE_ID_AMD_HUDSON2_SATA_IDE), board_ahci },
>>>>>> +	{ PCI_VDEVICE(AMD, PCI_DEVICE_ID_AMD_HUDSON2_SATA_AHCI), board_ahci_nodbdelay },
>>>>>
>>>>> Patch 1 introduces this macro in pci_ids.h, but it is used only here. So
>>>>> to keep with the current style in this structure, drop the macro (so
>>>>> drop patch 1).
>>>>
>>>> I wait for your answer of the second patch, and then I am going to sent v4.
>>>
>>> Let's use the numeric value. No macro definition needed.
>>
>> Alright. I am going to follow the maintainers wishes.
>>
>>>>>>     	{ PCI_VDEVICE(AMD, 0x7900), board_ahci }, /* AMD CZ */
>>>>>>     	{ PCI_VDEVICE(AMD, 0x7901), board_ahci_mobile }, /* AMD Green Sardine */
>>>>>>     	/* AMD is using RAID class only for ahci controllers */
>>>>
>>>> Do you have a AHCI device at hand, where you could also test if
>>>> everything works fine without the delay?
>>>
>>> Unfortunately, I do not have any board with this adapter.
>>
>> Sorry, we misunderstand each other. (I wrote a reply to my own patch [1].)
>>
>> I think the delay is not necessary for any modern AHCI controller. It’d
>> be great, if you could test, if it’s also true on the systems you have
>> by just skipping the delay.
> 
> I need to figure out how to safely test suspend/resume remotely (working
> from home) :)

Please note, I tested the cold bootup, where `sata_link_resume()` is 
also run.

> It would indeed be great to have the default as "no delay on resume" and
> add the delay only for chipsets that need it. However, it is unclear
> which chipset need the delay, right?

Yes, it’s unclear for what chipset (PHY?) it was added, as the git 
history i not available in the repository, and I have not found it yet.

> So I think we are stuck with switching chipsets to "no delay" one by
> one by testing. Once the majority of drivers are converted, we can
> reverse the default to be "no delay" and mark untested drivers as
> needing the delay.

For easy testing, a new CLI parameter to skip the delay might be handy.


Kind regards,

Paul


>> [1]: https://lore.kernel.org/linux-ide/20211227162658.11314-2-pmenzel@molgen.mpg.de/T/#m697d2121463a4c946730e6b83940e12d6d7e6700