linux-kernel - Re: [PATCH 13/13] accel/habanalabs: modify pci health check

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Message-ID: <31a0d18c-cea6-4d4e-b153-70f46c523b6e@habana.ai>
Date: Sat, 24 Feb 2024 19:20:50 +0000
From: Ofir Bitton <obitton@...ana.ai>
To: Carl Vanderlip <quic_carlv@...cinc.com>, Oded Gabbay <ogabbay@...nel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 13/13] accel/habanalabs: modify pci health check

On 24/02/2024 1:32, Carl Vanderlip wrote:
> 
> On 2/20/2024 8:01 AM, Oded Gabbay wrote:
>> From: Ofir Bitton <obitton@...ana.ai>
>>
>> Today we read PCI VENDOR-ID in order to make sure PCI link is
>> healthy. Apparently the VENDOR-ID might be stored on host and
>> hence, when we read it we might not access the PCI bus.
>> In order to make sure PCI health check is reliable, we will start
>> checking the DEVICE-ID instead.
> 
> What's keeping some system from caching that as well?

The PCI Controllers/switches we use in Gaudi family products might cache 
only the VENDOR-ID and not the DEVICE-ID.

> 
> Since this is checking for PCIe link health, it will be 0xFF when bad.
> Checking some part of Config Space that is writable would be more reliable.

Generally speaking I agree but there is no product in the Gaudi family 
with a 0xFF DEVICE-ID (nor there will be), so I think this approach is 
good enough for our use-case.

--
Ofir

> 
> -Carl V.