linux-kernel - Re: [PATCH V1] PCI: dwc: Use dev_info for PCIe link down event logging

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Message-ID: <5ffe3dfa-28a5-a5fc-0ae2-28927c39dc03@nvidia.com>
Date:   Wed, 14 Sep 2022 12:25:51 +0100
From:   Jon Hunter <jonathanh@...dia.com>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Vidya Sagar <vidyas@...dia.com>
Cc:     Bjorn Helgaas <helgaas@...nel.org>, jingoohan1@...il.com,
        gustavo.pimentel@...opsys.com, lpieralisi@...nel.org,
        robh@...nel.org, kw@...ux.com, bhelgaas@...gle.com,
        treding@...dia.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, kthota@...dia.com,
        mmaddireddy@...dia.com, sagar.tv@...il.com
Subject: Re: [PATCH V1] PCI: dwc: Use dev_info for PCIe link down event
 logging


On 14/09/2022 12:18, Manivannan Sadhasivam wrote:
> On Wed, Sep 14, 2022 at 04:32:10PM +0530, Vidya Sagar wrote:
>> Agree with Mani.
>> Not all form factors support PRSNT pin (Ex:- M.2 Key-M form factor) and even
>> if the slot form factor supports PRSNT, it is not mandatory to have a GPIO
>> routed to the PRSNT pin of the slot.
> 
> Right.
> 
>> Also, since these are development platforms, we wouldn't want to keep
>> changing a controller's status in the DT, instead want to know the device's
>> presence/absence (by way of link up) looking at the log.
>> In my honest opinion, I don't think the absence of a device in the slot
>> should be treated as an error.
>>
> 
> As I mentioned earlier, timeout can happen due to an issue with PHY layer
> also. In those cases, "dev_err()" is relevant.
> 
> And I also agree that absence of the device should not be treated as an
> error. But my question is, if you know that the slot is going to be
> empty always, why cannot you just disable it in dts?

I really don't think that makes sense from a usability perspective. You 
want to allow users to connect PCI cards and for them to work without 
having to update the DTB. I have plenty of open PCI slots on my PC and I 
would be a bit upset if someone told me I need to update the PC firmware 
each time I wanted to use a new slot.

Jon

-- 
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