Date:   Tue, 15 Feb 2022 13:27:59 +0100
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Hans de Goede <hdegoede@...hat.com>,
        Mario Limonciello <Mario.Limonciello@....com>
Cc:     linux-ide@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        Nehal-bakulchandra Shah <Nehal-bakulchandra.Shah@....com>
Subject: Re: [PATCH 1/2] ahci: Add Green Sardine vendor ID as
 board_ahci_mobile

Dear Hans,


Am 15.02.22 um 12:43 schrieb Hans de Goede:

> On 2/15/22 08:05, Paul Menzel wrote:

>> Am 14.02.22 um 17:07 schrieb Limonciello, Mario:
>>
>>> +Hans
>>>
>>>> (For the records, is part of Linux since 5.16-rc2 (commit 1527f69204fe).)
>>>>
>>>> Am 12.11.21 um 21:15 schrieb Mario Limonciello:
>>>>> AMD requires that the SATA controller be configured for devsleep in order
>>>>> for S0i3 entry to work properly.
>>>>>
>>>>> commit b1a9585cc396 ("ata: ahci: Enable DEVSLP by default on x86 with
>>>>> SLP_S0") sets up a kernel policy to enable devsleep on Intel mobile
>>>>> platforms that are using s0ix.  Add the PCI ID for the SATA controller in
>>>>> Green Sardine platforms to extend this policy by default for AMD based
>>>>> systems using s0i3 as well.
>>>>>
>>>>> Cc: Nehal-bakulchandra Shah <Nehal-bakulchandra.Shah@....com>
>>>>> BugLink:
>>>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugz
>>>> illa.kernel.org%2Fshow_bug.cgi%3Fid%3D214091&amp;data=04%7C01%7Cm
>>>> ario.limonciello%40amd.com%7Ca32a202d437544cd2cbb08d9ef9112c0%7C3d
>>>> d8961fe4884e608e11a82d994e183d%7C0%7C0%7C637804228648002522%7CU
>>>> nknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI
>>>> 6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=CbfImBnwc8uV1L5QRBuV
>>>> PLkP72wpS9yif1UbUwykhNI%3D&amp;reserved=0
>>
>> You have to love Microsoft Outlook.
>>
>>>>> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
>>>>> ---
>>>>>     drivers/ata/ahci.c | 1 +
>>>>>     1 file changed, 1 insertion(+)
>>>>>
>>>>> diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
>>>>> index d60f34718b5d..1e1167e725a4 100644
>>>>> --- a/drivers/ata/ahci.c
>>>>> +++ b/drivers/ata/ahci.c
>>>>> @@ -438,6 +438,7 @@ static const struct pci_device_id ahci_pci_tbl[] = {
>>>>>         /* AMD */
>>>>>         { PCI_VDEVICE(AMD, 0x7800), board_ahci }, /* AMD Hudson-2 */
>>>>>         { PCI_VDEVICE(AMD, 0x7900), board_ahci }, /* AMD CZ */
>>>>> +    { PCI_VDEVICE(AMD, 0x7901), board_ahci_mobile }, /* AMD Green Sardine */
>>>>
>>>> Aren't 0x7900 and 0x7901 the same device only in different modes? I
>>>> wonder, why different boards and different comments are used.
>>>
>>> No they aren't the same device in different modes.
>>>
>>> Reference:
>>> https://www.amd.com/en/support/tech-docs/processor-programming-reference-ppr-for-amd-family-19h-model-51h-revision-a1
>>> Page 33 has a table.
>>
>> That table misses 0x7900h. (Where can I find it?) coreboot has 0x7900 defined for Cezanne:
>>
>>      src/include/device/pci_ids.h:#define PCI_DEVICE_ID_AMD_CZ_SATA  0x7900
>>      src/soc/amd/stoneyridge/include/soc/pci_devs.h: * SATA_IDE_IDEVID              0x7900
>>
>> The PCI database too [3]:
>>
>>> FCH SATA Controller [IDE mode]
>>
>>
>>>> Additionally, the device 0x7901 is also present in desktop systems like
>>>> Dell OptiPlex 5055 and MSI B350 MORTAR. Is `board_ahci_mobile` the right
>>>> board then? Or should the flag `AHCI_HFLAG_IS_MOBILE` be renamed to
>>>> avoid confusion?
>>>
>>> Are you having a problem or just want clarity in the enum definition?
>>
>> It’s more about clarity, and understanding the two different entries.
>>
>>> This was introduced by Hans in commit ebb82e3c79d2a to set LPM policy properly
>>> for a number of mobile devices.
>>>
>>> My opinion here is that the policy being for "mobile" devices only is short sighted as power
>>> consumption policy on desktops is also relevant as OEMs ship desktops that need to meet
>>> various power regulations for those too.
>>>
>>> So I would be in the camp for renaming the flags.
>>
>> Why can’t the LPM policy, if available(?), not be set for `board_ahci` by default, so `board_ahci_mobile` could be removed?
> 
> When I added this, which was around the Haswell / Broadwell times, enabling
> LPM on mobile devices was not so much important for the direct power-saving,
> but to allow the entire package (integrated southbridge-ish) to go to deeper
> sleep (aka PC) states.
> 
> Without this laptops would drain their batteries much faster, but at the same
> time there were reports of LPM causing crashes and data corruption on some
> systems, also see the list of ATA ids with a ATA_HORKAGE_NOLPM flag in
> drivers/ata/libata-core.c . Which was added and grown over time to allow
> enabling LPM by default without causing regressions.

This seems to be related to the hard driver though, and not the chipset?

> So when adding support for enabling LPM modes by default, to get the
> desired power-savings by default I tried to do this on a minimal set of
> devices, to avoid causing regressions.
> 
> Another factor here is that in some cases LPM related issues went away
> after either BIOS or disk/ssd firmware updates. So the motherboard firmware
> is also a factor here and enabling LPM by default on non laptop(ish)
> motherboards has never been tested.
> 
> Also enabling some of the deeper LPM modes comes at a latency cost which
> may be undesirable at servers. Note this just sets the initial default
> LPM mode, this can always be changed by userspace later.

Thank you for the elaborate explanation. What do you suggest in regards 
the 1022:7901, present in laptops and desktop systems?

>>>>>         /* AMD is using RAID class only for ahci controllers */
>>>>>         { PCI_VENDOR_ID_AMD, PCI_ANY_ID, PCI_ANY_ID, PCI_ANY_ID,
>>>>>           PCI_CLASS_STORAGE_RAID << 8, 0xffffff, board_ahci },


Kind regards,

Paul


>> [1]: https://review.coreboot.org/10418
>> [2]: https://review.coreboot.org/20200
>> [3]: https://pci-ids.ucw.cz/read/PC/1022/7900

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