From: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
To: Lorenzo Pieralisi <lpieralisi@kernel.org>
Cc: Rob Herring <robh@kernel.org>, Bjorn Helgaas <helgaas@kernel.org>,
Jon Hunter <jonathanh@nvidia.com>,
Vidya Sagar <vidyas@nvidia.com>,
Jingoo Han <jingoohan1@gmail.com>,
Gustavo Pimentel <gustavo.pimentel@synopsys.com>,
Krzysztof Wilczynski <kw@linux.com>,
Bjorn Helgaas <bhelgaas@google.com>,
Thierry Reding <treding@nvidia.com>,
PCI <linux-pci@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Krishna Thota <kthota@nvidia.com>,
Manikanta Maddireddy <mmaddireddy@nvidia.com>,
sagar.tv@gmail.com
Subject: Re: [PATCH V1] PCI: dwc: Use dev_info for PCIe link down event logging
Date: Thu, 27 Oct 2022 16:33:16 +0530 [thread overview]
Message-ID: <20221027110316.GA76627@thinkpad> (raw)
In-Reply-To: <Y1pRtoLdWsDONsok@lpieralisi>
On Thu, Oct 27, 2022 at 11:39:02AM +0200, Lorenzo Pieralisi wrote:
> 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@linaro.org> 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@nvidia.com>
> > > > > 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.
>
> I read this as "trying to bring the link up is mandatory because
> we can't detect an empty slot, therefore ~1ms delay during boot
> is unavoidable" and on that Rob's suggestion applies.
>
Right. Rob's suggestion came as areply to my worry on waiting for link up
during boot.
> Just to understand where this thread is going. The suggestion
> above does not change the aim of this patch, that seems reasonable
> to me and it makes sense even if/when what Rob is suggesting is
> implemented.
>
> Is that correct ?
>
Yes, Rob's suggestion makes sense to me. And it has to be implemented as a
separate patch but this patch itself is required to demote the error log to
debug.
Thanks,
Mani
> Thanks,
> Lorenzo
--
மணிவண்ணன் சதாசிவம்
next prev parent reply other threads:[~2022-10-27 11:03 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-13 10:12 [PATCH V1] PCI: dwc: Use dev_info for PCIe link down event logging Vidya Sagar
2022-09-13 16:51 ` Manivannan Sadhasivam
2022-09-13 17:00 ` Jon Hunter
2022-09-13 20:07 ` Bjorn Helgaas
2022-09-14 6:24 ` Manivannan Sadhasivam
2022-09-14 11:02 ` Vidya Sagar
2022-09-14 11:18 ` Manivannan Sadhasivam
2022-09-14 11:25 ` Jon Hunter
2022-09-14 11:43 ` Manivannan Sadhasivam
2022-09-14 11:52 ` Jon Hunter
2022-09-14 12:44 ` Krzysztof Wilczyński
2022-09-14 13:45 ` Manivannan Sadhasivam
2022-09-14 14:52 ` Krzysztof Wilczyński
2022-09-14 15:11 ` Jon Hunter
2022-09-15 14:16 ` Rob Herring
2022-09-15 14:52 ` Manivannan Sadhasivam
2022-09-26 10:29 ` Vidya Sagar
2022-10-03 11:25 ` Vidya Sagar
2022-10-04 12:53 ` Rob Herring
2022-10-10 6:02 ` Vidya Sagar
2022-10-26 18:06 ` Rob Herring
2022-10-27 9:39 ` Lorenzo Pieralisi
2022-10-27 11:03 ` Manivannan Sadhasivam [this message]
2022-09-14 6:12 ` Manivannan Sadhasivam
2022-09-15 10:44 ` Manivannan Sadhasivam
2022-10-18 6:21 ` Jon Hunter
2022-10-18 16:43 ` Bjorn Helgaas
2022-10-26 11:39 ` Jon Hunter
2022-10-26 12:33 ` Lorenzo Pieralisi
2022-10-27 9:55 ` Ben Dooks
2022-10-27 11:05 ` Manivannan Sadhasivam
2022-11-10 15:40 ` Lorenzo Pieralisi
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