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

[Vidya Sagar]

Hi Bjorn / Lorenzo,
Just checking if there are any more comments for this patch? If not, are 
we good to take it?

Thanks,
Vidya Sagar

On 9/26/2022 3:59 PM, Vidya Sagar wrote:
> Hi,
> Just checking if we are good with this patch or does it need any further 
> modifications?
>
> Thanks,
> Vidya Sagar
>
> On 9/15/2022 8:22 PM, Manivannan Sadhasivam wrote:
> > External email: Use caution opening links or attachments
> >
> >
> > On Thu, Sep 15, 2022 at 09:16:27AM -0500, Rob Herring wrote:
> > > On Wed, Sep 14, 2022 at 1:24 AM Manivannan Sadhasivam
> > > <manivannan.sadhasivam@xxxxxxxxxx> wrote:
> > > > On Tue, Sep 13, 2022 at 03:07:46PM -0500, Bjorn Helgaas wrote:
> > > > > On Tue, Sep 13, 2022 at 06:00:30PM +0100, Jon Hunter wrote:
> > > > > > On 13/09/2022 17:51, Manivannan Sadhasivam wrote:
> > > > > > > On Tue, Sep 13, 2022 at 03:42:37PM +0530, Vidya Sagar wrote:
> > > > > > > > Some of the platforms (like Tegra194 and Tegra234) have open 
> > > > > > > > slots and
> > > > > > > > not having an endpoint connected to the slot is not an error.
> > > > > > > > So, changing the macro from dev_err to dev_info to log the event.
> > > > > > >
> > > > > > > But the link up not happening is an actual error and -ETIMEDOUT 
> > > > > > > is being
> > > > > > > returned. So I don't think the log severity should be changed.
> > > > > >
> > > > > > Yes it is an error in the sense it is a timeout, but reporting an 
> > > > > > error
> > > > > > because nothing is attached to a PCI slot seems a bit noisy. 
> > > > > > Please note
> > > > > > that a similar change was made by the following commit and it also 
> > > > > > seems
> > > > > > appropriate here ...
> > > > > >
> > > > > > commit 4b16a8227907118e011fb396022da671a52b2272
> > > > > > Author: Manikanta Maddireddy <mmaddireddy@xxxxxxxxxx>
> > > > > > Date:   Tue Jun 18 23:32:06 2019 +0530
> > > > > >
> > > > > >      PCI: tegra: Change link retry log level to debug
> > > > > >
> > > > > >
> > > > > > BTW, we check for error messages in the dmesg output and this is a 
> > > > > > new error
> > > > > > seen as of Linux v6.0 and so this was flagged in a test. We can 
> > > > > > ignore the
> > > > > > error, but in this case it seem more appropriate to make this a 
> > > > > > info or
> > > > > > debug level print.
> > > > >
> > > > > Can you tell whether there's a device present, e.g., via Slot Status
> > > > > Presence Detect?  If there's nothing in the slot, I don't know why we
> > > > > would print anything at all.  If a card is present but there's no
> > > > > link, that's probably worthy of dev_info() or even dev_err().
> > > >
> > > > I don't think all form factors allow for the PRSNT pin to be wired up,
> > > > so we cannot know if the device is actually present in the slot or 
> > > > not all
> > > > the time. Maybe we should do if the form factor supports it?
> > > >
> > > > > I guess if you can tell the slot is empty, there's no point in even
> > > > > trying to start the link, so you could avoid both the message and the
> > > > > timeout by not even calling dw_pcie_wait_for_link().
> > > >
> > > > Right. There is an overhead of waiting for ~1ms during boot.
> > >
> > > Async probe should mitigate that, right? Saravana is working toward
> > > making that the default instead of opt in, but you could opt in now.
> >
> > No. The delay is due to the DWC core waiting for link up that depends on
> > the PCIe device to be present on the slot. The driver probe order
> > doesn't apply here.
> >
> > Thanks,
> > Mani
> >
> > > Rob