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

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Date:   Wed, 11 May 2022 16:00:05 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Peter Geis <pgwipeout@...il.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 10:26:20AM -0400, Peter Geis wrote:
> 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.

Ok. I will take patches [1-3], dts changes will have to go via
platform trees, I hope that's fine.

Thanks,
Lorenzo

> > 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
> > >