linux-kernel - Re: [PATCH] PCI: qcom: Enable clocks only after PARF

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Date:   Mon, 11 Jul 2022 14:22:29 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Christian Marangi <ansuelsmth@...il.com>
Cc:     Stanimir Varbanov <svarbanov@...sol.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Robert Marko <robimarko@...il.com>
Subject: Re: [PATCH] PCI: qcom: Enable clocks only after PARF_PHY setup for
 rev 2.1.0

[+cc Robert since I resolved a conflict in his patch, -cc stable]

On Sat, Jul 09, 2022 at 03:03:34AM +0200, Christian Marangi wrote:
> On Fri, Jul 08, 2022 at 06:01:55PM -0500, Bjorn Helgaas wrote:
> > On Sat, Jul 09, 2022 at 12:27:43AM +0200, Christian Marangi wrote:
> > > We currently enable clocks BEFORE we write to PARF_PHY_CTRL reg to
> > > enable clocks and resets. This case the driver to never set to a ready
> > > state with the error 'Phy link never came up'.
> > > 
> > > This in fact is caused by the phy clock getting enabled before setting
> > > the required bits in the PARF regs.
> > > 
> > > A workaround for this was set but with this new discovery we can drop
> > > the workaround and use a proper solution to the problem by just enabling
> > > the clock only AFTER the PARF_PHY_CTRL bit is set.
> > > 
> > > This correctly setup the pcie line and makes it usable even when a
> > > bootloader leave the pcie line to a underfined state.
> > 
> > Is "pcie" here a signal name?  Maybe this refers to the "PCIe link"?
> 
> no i was referring to PCIe link. Fell free to fix it if it's not a
> problem (or if you want i can just resend)

I fixed it.

> Think something went wrong in the rebase as the patch fixup is reverted.
> 
> 11946f8b6e77a6794c111aafef7772e9967d9a54 is still wrong.
> 
> clk_bulk_prepare_enable must be after 
> writel(val, pcie->parf + PCIE20_PARF_PHY_CTRL);
> so in the post init.

My error, sorry.  I updated it, current head:

  1a88605a3efd ("dt-bindings: PCI: qcom: Fix description typo")

Robert, your patch that I updated is:

https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/commit/?h=pci/ctrl/qcom-pending&id=cdb32283bcf202d0db512abb80794056d44e7e9f

It would still be nice to get an ack from one of the maintainers for
this.

Bjorn