linux-kernel - Re: [PATCH v2] PCI: qcom: fix IPQ8074 Gen2 support

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Message-ID: <20220621211604.GA1334281@bhelgaas>
Date:   Tue, 21 Jun 2022 16:16:04 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Robert Marko <robimarko@...il.com>, svarbanov@...sol.com,
        agross@...nel.org, bjorn.andersson@...aro.org,
        lpieralisi@...nel.org, robh@...nel.org, kw@...ux.com,
        bhelgaas@...gle.com, p.zabel@...gutronix.de, jingoohan1@...il.com,
        linux-pci@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, johan+linaro@...nel.org
Subject: Re: [PATCH v2] PCI: qcom: fix IPQ8074 Gen2 support

On Tue, Jun 21, 2022 at 11:45:12PM +0300, Dmitry Baryshkov wrote:
> On Tue, 21 Jun 2022 at 23:32, Bjorn Helgaas <helgaas@...nel.org> wrote:
> > On Tue, Jun 21, 2022 at 01:23:30PM +0200, Robert Marko wrote:
> > > IPQ8074 has one Gen2 and one Gen3 port, currently the Gen2 port will
> > > cause the system to hang as its using DBI registers in the .init
> > > and those are only accesible after phy_power_on().
> >
> > Is the fact that IPQ8074 has both a Gen2 and a Gen3 port relevant to
> > this patch?  I don't see the connection.
> >
> > I see that qcom_pcie_host_init() does:
> >
> >   qcom_pcie_host_init
> >     pcie->cfg->ops->init(pcie)
> >     phy_power_on(pcie->phy)
> >     pcie->cfg->ops->post_init(pcie)
> >
> > and that you're moving DBI register accesses from
> > qcom_pcie_init_2_3_3() to qcom_pcie_post_init_2_3_3().
> >
> > But I also see DBI register accesses in other .init() functions:
> >
> >   qcom_pcie_init_2_1_0
> >   qcom_pcie_init_1_0_0      (oddly out of order)
> >   qcom_pcie_init_2_3_2
> >   qcom_pcie_init_2_4_0
> >
> > Why do these accesses not need to be moved?  I assume it's because
> > pcie->phy is an optional PHY and phy_power_on() does nothing on those
> > controllers?
> >
> > Whatever the reason, I think the DBI accesses should be done
> > consistently in .post_init().  I see that Dmitry's previous patches
> > removed all those .post_init() functions, but I think the consistency
> > is worth having.
> >
> > Perhaps we could reorder the patches so this patch comes first, moves
> > the DBI accesses into .post_init(), then Dmitry's patches could be
> > rebased on top to drop the clock handling?
> 
> I don't think there is a need to reorder patches. My patches do not
> remove support for post_init(), they drop the callbacks code. Thus one
> can reinstate necessary code back.

There's not a *need* to reorder them, but I think it would make the
patches smaller and more readable because we wouldn't be removing and
then re-adding the functions.