linux-kernel - Re: [PATCH v5] libata: Add ATA_HORKAGE_NO_NCQ_ON

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Date:   Thu, 02 Sep 2021 15:01:55 -0400
From:   "Martin K. Petersen" <martin.petersen@...cle.com>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Kate Hsuan <hpa@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        Damien Le Moal <damien.lemoal@....com>,
        Tor Vic <torvic9@...lbox.org>, linux-ide@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] libata: Add ATA_HORKAGE_NO_NCQ_ON_AMD for Samsung
 860 and 870 SSD.

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.

> So lets wait a bit for some more info to become available and then
> I think we need a v6 with s/AMD/ATI/ (everywhere, also in the name
> of the horkage-flag, the cmdline options, etc.).

Sounds good!

-- 
Martin K. Petersen	Oracle Linux Engineering