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Date:   Tue, 15 Feb 2022 13:55:03 +0100
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Subject: Re: [PATCH 1/2] ahci: Add Green Sardine vendor ID as
 board_ahci_mobile
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To:     "Limonciello, Mario" <Mario.Limonciello@amd.com>,
        Paul Menzel <pmenzel@molgen.mpg.de>
Cc:     "linux-ide@vger.kernel.org" <linux-ide@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Damien Le Moal <damien.lemoal@opensource.wdc.com>,
        "Shah, Nehal-bakulchandra" <Nehal-bakulchandra.Shah@amd.com>
References: <20211112201539.17377-1-mario.limonciello@amd.com>
 <960946b8-8f73-9f81-735a-64e5cc555a9c@molgen.mpg.de>
 <DM4PR12MB516853204C9D7E7EAAFBC91FE2339@DM4PR12MB5168.namprd12.prod.outlook.com>
From:   Hans de Goede <hdegoede@redhat.com>
In-Reply-To: <DM4PR12MB516853204C9D7E7EAAFBC91FE2339@DM4PR12MB5168.namprd12.prod.outlook.com>
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Hi,

On 2/14/22 17:07, Limonciello, Mario wrote:
> [Public]
> 
> +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@amd.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
>>> Signed-off-by: Mario Limonciello <mario.limonciello@amd.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.
> 
>>
>> 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?
> 
> 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.

I have no objection against renaming the flags, maybe rename "mobile" to
"enable_lpm_by_default" ? That is a bit long, but it is what it is all
about. Alternatively we could go with "low_power" but that feels much less
descriptive.

Regards,

Hans