linux-kernel - Re: [PATCH v9 2/5] PCI: rockchip-dwc: Reset core at driver probe

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Date:   Wed, 11 May 2022 10:26:20 -0400
From:   Peter Geis <pgwipeout@...il.com>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:     "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Marc Zyngier <maz@...nel.org>, PCI <linux-pci@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        arm-mail-list <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Nicolas Frattaroli <frattaroli.nicolas@...il.com>
Subject: Re: [PATCH v9 2/5] PCI: rockchip-dwc: Reset core at driver probe

On Wed, May 11, 2022 at 9:50 AM Lorenzo Pieralisi
<lorenzo.pieralisi@....com> wrote:
>
> On Fri, Apr 29, 2022 at 08:38:28AM -0400, Peter Geis wrote:
> > The PCIe controller is in an unknown state at driver probe. This can
> > lead to undesireable effects when the driver attempts to configure the
> > controller.
> >
> > Prevent issues in the future by resetting the core during probe.
> >
> > Signed-off-by: Peter Geis <pgwipeout@...il.com>
> > Tested-by: Nicolas Frattaroli <frattaroli.nicolas@...il.com>
> > ---
> >  drivers/pci/controller/dwc/pcie-dw-rockchip.c | 23 ++++++++-----------
> >  1 file changed, 10 insertions(+), 13 deletions(-)
>
> I fear that the controller reset behaviour is bootloader/firmware
> dependent.
>
> Are we sure we are not triggering any regressions by resetting the
> controller in the middle of probe (aka is the driver implicitly
> relying on existing behaviour on systems that are not the ones
> you are testing on) ?
>
> Just asking, the rockchip maintainers should be able to answer this
> question.

This is a new driver with no current users, this series enables the
first user. It does not support ACPI nor any sort of handoff at this
time.

>
> Thanks,
> Lorenzo
>
> > diff --git a/drivers/pci/controller/dwc/pcie-dw-rockchip.c b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
> > index c9b341e55cbb..faedbd6ebc20 100644
> > --- a/drivers/pci/controller/dwc/pcie-dw-rockchip.c
> > +++ b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
> > @@ -152,6 +152,11 @@ static int rockchip_pcie_resource_get(struct platform_device *pdev,
> >       if (IS_ERR(rockchip->rst_gpio))
> >               return PTR_ERR(rockchip->rst_gpio);
> >
> > +     rockchip->rst = devm_reset_control_array_get_exclusive(&pdev->dev);
> > +     if (IS_ERR(rockchip->rst))
> > +             return dev_err_probe(&pdev->dev, PTR_ERR(rockchip->rst),
> > +                                  "failed to get reset lines\n");
> > +
> >       return 0;
> >  }
> >
> > @@ -182,18 +187,6 @@ static void rockchip_pcie_phy_deinit(struct rockchip_pcie *rockchip)
> >       phy_power_off(rockchip->phy);
> >  }
> >
> > -static int rockchip_pcie_reset_control_release(struct rockchip_pcie *rockchip)
> > -{
> > -     struct device *dev = rockchip->pci.dev;
> > -
> > -     rockchip->rst = devm_reset_control_array_get_exclusive(dev);
> > -     if (IS_ERR(rockchip->rst))
> > -             return dev_err_probe(dev, PTR_ERR(rockchip->rst),
> > -                                  "failed to get reset lines\n");
> > -
> > -     return reset_control_deassert(rockchip->rst);
> > -}
> > -
> >  static const struct dw_pcie_ops dw_pcie_ops = {
> >       .link_up = rockchip_pcie_link_up,
> >       .start_link = rockchip_pcie_start_link,
> > @@ -222,6 +215,10 @@ static int rockchip_pcie_probe(struct platform_device *pdev)
> >       if (ret)
> >               return ret;
> >
> > +     ret = reset_control_assert(rockchip->rst);
> > +     if (ret)
> > +             return ret;
> > +
> >       /* DON'T MOVE ME: must be enable before PHY init */
> >       rockchip->vpcie3v3 = devm_regulator_get_optional(dev, "vpcie3v3");
> >       if (IS_ERR(rockchip->vpcie3v3)) {
> > @@ -241,7 +238,7 @@ static int rockchip_pcie_probe(struct platform_device *pdev)
> >       if (ret)
> >               goto disable_regulator;
> >
> > -     ret = rockchip_pcie_reset_control_release(rockchip);
> > +     ret = reset_control_deassert(rockchip->rst);
> >       if (ret)
> >               goto deinit_phy;
> >
> > --
> > 2.25.1
> >