linux-kernel - Re: [PATCH v2] PCI: dra7xx: Fix reset behaviour

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Date:   Tue, 22 Jun 2021 13:06:27 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Luca Ceresoli <luca@...aceresoli.net>
Cc:     Kishon Vijay Abraham I <kishon@...com>, linux-pci@...r.kernel.org,
        linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v2] PCI: dra7xx: Fix reset behaviour

Hello!

On Tuesday 22 June 2021 12:57:22 Luca Ceresoli wrote:
> Nothing happened after a few weeks... I understand that knowing the
> correct reset timings is relevant, but unfortunately I cannot help much
> in finding out the correct values.
> 
> However I'm wondering what should happen to this patch. It *does* fix a
> real bug, but potentially with an incorrect or non-optimal usleep range.
> Do we really want to ignore a bugfix because we are not sure about how
> long this delay should be?

As there is no better solution right now, I'm fine with your patch. But
patch needs to be approved by Lorenzo, so please wait for his final
answer.

I would suggest to add a comment for call "usleep_range(1000, 2000);"
that you have chosen some "random" values which worked fine on your
setup and that they fix mentioned bug. Comment just to mark this sleep
code that is suboptimal / not-so-correct and to prevent other people to
copy+paste this code into other (new) drivers...