linux-kernel - Re: [PATCH v1] drivers: pci: introduce configurable delay for Rockchip PCIe bus scan

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Message-Id: <CSKG4WDA4MVH.1RVYIN4NYH4EA@vincent-arch>
Date:   Fri, 12 May 2023 18:40:03 +0200
From:   "Vincenzo Palazzo" <vincenzopalazzodev@...il.com>
To:     "Bjorn Helgaas" <helgaas@...nel.org>
Cc:     <linux-pci@...r.kernel.org>, <robh@...nel.org>, <heiko@...ech.de>,
        <kw@...ux.com>, <shawn.lin@...k-chips.com>,
        <linux-kernel@...r.kernel.org>, <lgirdwood@...il.com>,
        <linux-rockchip@...ts.infradead.org>, <broonie@...nel.org>,
        <bhelgaas@...gle.com>,
        <linux-kernel-mentees@...ts.linuxfoundation.org>,
        <lpieralisi@...nel.org>, <linux-arm-kernel@...ts.infradead.org>,
        "Dan Johansen" <strit@...jaro.org>
Subject: Re: [PATCH v1] drivers: pci: introduce configurable delay for
 Rockchip PCIe bus scan

>
> Thanks for raising this issue.  Let's see what we can do to address
> it.
>
> On Tue, May 09, 2023 at 05:39:12PM +0200, Vincenzo Palazzo wrote:
> > Add a configurable delay to the Rockchip PCIe driver to address
> > crashes that occur on some old devices, such as the Pine64 RockPro64.
> > 
> > This issue is affecting the ARM community, but there is no
> > upstream solution for it yet.
>
> It sounds like this happens with several endpoints, right?  And I
> assume the endpoints work fine in other non-Rockchip systems?  If
> that's the case, my guess is the problem is with the Rockchip host
> controller and how it's initialized, not with the endpoints.
>
> The only delays and timeouts I see in the driver now are in
> rockchip_pcie_host_init_port(), where it waits for link training to
> complete.  I assume the link training did completely successfully
> since you don't mention either a gen1 or gen2 timeout (although the
> gen2 message is a dev_dbg() that normally wouldn't go to the console).
>
> I don't know that the spec contains a retrain timeout value.  Several
> other drivers use 1 second, while rockchip uses 500ms (for example,
> see LINK_RETRAIN_TIMEOUT and LINK_UP_TIMEOUT).
>
> I think we need to understand the issue better before adding a DT
> property and a module parameter.  Those are hard for users to deal
> with.  If we can figure out a value that works for everybody, it would
> be better to just hard-code it in the driver and use that all the
> time.
>
> A few minor style/formatting comments below just for future reference:

Due the recent email I think it is worth make a version 2 of this
patch with your suggestion? and iterate over it another time?

Cheers!

Vincent.