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

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Message-ID: <CAOX2RU7idTVcW6ivqs3V_Ep33RoHZs1zt0jav-_z2D7xpKJstw@mail.gmail.com>
Date:   Tue, 21 Jun 2022 23:05:17 +0200
From:   Robert Marko <robimarko@...il.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     svarbanov@...sol.com, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        lpieralisi@...nel.org, Rob Herring <robh@...nel.org>, kw@...ux.com,
        Bjorn Helgaas <bhelgaas@...gle.com>, p.zabel@...gutronix.de,
        jingoohan1@...il.com, linux-pci@...r.kernel.org,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        johan+linaro@...nel.org
Subject: Re: [PATCH v2] PCI: qcom: fix IPQ8074 Gen2 support

On Tue, 21 Jun 2022 at 22:32, 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.

Hi Bjorn,
Not really, I can remove it from the description as this only affects the Gen2
port, Gen3 support is dependant on the IPQ6018 support getting merged as
it uses the same controller.

>
> 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?

As far as I could figure out from QCA-s 5.4 kernel, various commits, and QCA-s
attempts to solve this already upstream the Gen2 controller in IPQ8074 is a bit
special and requires the PHY to be powered on before DBI could be accessed or
else the board will hang as it does for me.

I can only assume that this is an IPQ8074-specific quirk and other IP-s are not
affected like this, so they were not broken.

>
> 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?
>
> > So solve this by splitting the DBI read/writes to .post_init.

I am open to anything to get this fixed properly, you are gonna need
to point me in the right direction
as I am really new to PCI.

Regards,
Robert
> >
> > Fixes: a0fd361db8e5 ("PCI: dwc: Move "dbi", "dbi2", and "addr_space" resource setup into common code")
> > Signed-off-by: Robert Marko <robimarko@...il.com>
> > ---
> > Changes in v2:
> > * Rebase onto next-20220621
> > ---
> >  drivers/pci/controller/dwc/pcie-qcom.c | 48 +++++++++++++++-----------
> >  1 file changed, 28 insertions(+), 20 deletions(-)
> >
> > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> > index 51fed83484af..da6d79d61397 100644
> > --- a/drivers/pci/controller/dwc/pcie-qcom.c
> > +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> > @@ -1061,9 +1061,7 @@ static int qcom_pcie_init_2_3_3(struct qcom_pcie *pcie)
> >       struct qcom_pcie_resources_2_3_3 *res = &pcie->res.v2_3_3;
> >       struct dw_pcie *pci = pcie->pci;
> >       struct device *dev = pci->dev;
> > -     u16 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> >       int i, ret;
> > -     u32 val;
> >
> >       for (i = 0; i < ARRAY_SIZE(res->rst); i++) {
> >               ret = reset_control_assert(res->rst[i]);
> > @@ -1120,6 +1118,33 @@ static int qcom_pcie_init_2_3_3(struct qcom_pcie *pcie)
> >               goto err_clk_aux;
> >       }
> >
> > +     return 0;
> > +
> > +err_clk_aux:
> > +     clk_disable_unprepare(res->ahb_clk);
> > +err_clk_ahb:
> > +     clk_disable_unprepare(res->axi_s_clk);
> > +err_clk_axi_s:
> > +     clk_disable_unprepare(res->axi_m_clk);
> > +err_clk_axi_m:
> > +     clk_disable_unprepare(res->iface);
> > +err_clk_iface:
> > +     /*
> > +      * Not checking for failure, will anyway return
> > +      * the original failure in 'ret'.
> > +      */
> > +     for (i = 0; i < ARRAY_SIZE(res->rst); i++)
> > +             reset_control_assert(res->rst[i]);
> > +
> > +     return ret;
> > +}
> > +
> > +static int qcom_pcie_post_init_2_3_3(struct qcom_pcie *pcie)
> > +{
> > +     struct dw_pcie *pci = pcie->pci;
> > +     u16 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> > +     u32 val;
> > +
> >       writel(SLV_ADDR_SPACE_SZ,
> >               pcie->parf + PCIE20_v3_PARF_SLV_ADDR_SPACE_SIZE);
> >
> > @@ -1147,24 +1172,6 @@ static int qcom_pcie_init_2_3_3(struct qcom_pcie *pcie)
> >               PCI_EXP_DEVCTL2);
> >
> >       return 0;
> > -
> > -err_clk_aux:
> > -     clk_disable_unprepare(res->ahb_clk);
> > -err_clk_ahb:
> > -     clk_disable_unprepare(res->axi_s_clk);
> > -err_clk_axi_s:
> > -     clk_disable_unprepare(res->axi_m_clk);
> > -err_clk_axi_m:
> > -     clk_disable_unprepare(res->iface);
> > -err_clk_iface:
> > -     /*
> > -      * Not checking for failure, will anyway return
> > -      * the original failure in 'ret'.
> > -      */
> > -     for (i = 0; i < ARRAY_SIZE(res->rst); i++)
> > -             reset_control_assert(res->rst[i]);
> > -
> > -     return ret;
> >  }
> >
> >  static int qcom_pcie_get_resources_2_7_0(struct qcom_pcie *pcie)
> > @@ -1598,6 +1605,7 @@ static const struct qcom_pcie_ops ops_2_4_0 = {
> >  static const struct qcom_pcie_ops ops_2_3_3 = {
> >       .get_resources = qcom_pcie_get_resources_2_3_3,
> >       .init = qcom_pcie_init_2_3_3,
> > +     .post_init = qcom_pcie_post_init_2_3_3,
> >       .deinit = qcom_pcie_deinit_2_3_3,
> >       .ltssm_enable = qcom_pcie_2_3_2_ltssm_enable,
> >  };
> > --
> > 2.36.1
> >