Re: [PATCH v5] libata: Add ATA_HORKAGE_NO_NCQ_ON_AMD for Samsung 860 and 870 SSD.

[Hans de Goede]

Hi,

On 9/2/21 9:01 PM, Martin K. Petersen wrote:
> 
> Hans,
> 
>> So it looks like we actually need to disable NCQ for Samsung 860/870
>> devices when the SATA controller has a vendor-id of PCI_VENDOR_ID_ATI
>> rather then AMD.
> 
> That's another great data point!
> 
> I wonder if there actually is a Samsung problem (given that these drives
> work fine on other controllers). Or if it is just the queued trim
> handling that's broken on 1002:4391 controllers from ATI.
> 
> When I originally experimented with queued trim I had systems I could
> not get to work. But queued trim worked fine when the same drives were
> connected to more modern chipsets (note that this was "did not work at
> all" as opposed to "randomly corrupting data").
>
> Do we have any evidence at all of queued trim working with non-Samsung
> drives on these controllers? Not sure how many modern SATA drives
> actually implement this feature. Maybe the reason we see Samsung drives
> in the bug reports is due to a combination of popularity and the fact
> that these drives actually implement queued trim support.

The Samsung 860 / 870 series causing issues when queued trim support
is enabled are quite wide-spread, covering many different controller
models from all well known controller vendors (Intel, Asmedia, Marvell
and AMD). So disabling queued-trim support definitely is the right
thing to do (and we should have done so a long time ago, I am to
blame for this not being done sooner).

As for your theory that it is really a problem with the controller
and not the the SSDs, I honestly do not know, but I doubt it,
there are no such reports with any other vendor's SSD or newer
Samsung models, so this seems unlikely.

Regards,

Hans