RE: [PATCH v6 7/8] PCI: imx6: Disable enabled clocks and regulators after link is down

[Hongxing Zhu]

> -----Original Message-----
> From: Fabio Estevam <festevam@xxxxxxxxx>
> Sent: 2022年2月8日 18:10
> To: Hongxing Zhu <hongxing.zhu@xxxxxxx>
> Cc: Lucas Stach <l.stach@xxxxxxxxxxxxxx>; Bjorn Helgaas
> <bhelgaas@xxxxxxxxxx>; Mark Brown <broonie@xxxxxxxxxx>; Lorenzo Pieralisi
> <lorenzo.pieralisi@xxxxxxx>; Jingoo Han <jingoohan1@xxxxxxxxx>;
> linux-pci@xxxxxxxxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>; moderated
> list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE
> <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>; linux-kernel
> <linux-kernel@xxxxxxxxxxxxxxx>; Sascha Hauer <kernel@xxxxxxxxxxxxxx>
> Subject: Re: [PATCH v6 7/8] PCI: imx6: Disable enabled clocks and regulators
> after link is down
> 
> Hi Richard,
> 
> On Tue, Feb 8, 2022 at 12:57 AM Richard Zhu <hongxing.zhu@xxxxxxx>
> wrote:
> >
> > Since i.MX PCIe doesn't support the hot-plug, and to save power
> > consumption as much as possible. Return error and disable the enabled
> > clocks and regulators when link is down,.
> 
> It is OK to disable clocks and regulators, but I don't think we should return an
> error on dw_pcie_wait_for_link() failure.
Hi Fabio:
Thanks for your review.
How do we know there is a link down, if we don't return an error on the
 dw_pcie_wait_for_link() after host_init callback.

Do you mean that we should ignore the return of dw_pcie_host_init() and
finish the _probe without an error return?
Best Regards
Richard
> 
> Please check:
> 
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kern
> el.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Flpieralisi%2Fpci.git%2Fco
> mmit%2F%3Fh%3Dpci%2Fimx6%26id%3Df81f095e87715e198471f4653952fe
> 5e3f824874&amp;data=04%7C01%7Chongxing.zhu%40nxp.com%7C3630184
> 5833b41f1f70a08d9eaeb2519%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C
> 0%7C0%7C637799117928160088%7CUnknown%7CTWFpbGZsb3d8eyJWIjoi
> MC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C300
> 0&amp;sdata=UUF%2FbZNUy7T4d89sJKnPvN6kNxEB%2FhnSUbIze7ilUOA%3D
> &amp;reserved=0
> 
> and
> 
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kern
> el.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Flpieralisi%2Fpci.git%2Fco
> mmit%2F%3Fh%3Dpci%2Fimx6%26id%3D886a9c134755&amp;data=04%7C0
> 1%7Chongxing.zhu%40nxp.com%7C36301845833b41f1f70a08d9eaeb2519%7
> C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C63779911792816008
> 8%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiL
> CJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=FO0wr4IE%2BA6YCu
> f0Lal2az8FRkK8ZvHkmLM%2F5zlosZY%3D&amp;reserved=0
> 
> as to why all the dwc PCI drivers should treat dw_pcie_wait_for_link()
> uniformly.
> 
> 
> 
> 
> 
> 
> >
> > Add a new host_exit() callback for i.MX PCIe driver to disable the
> > enabled clocks, regulators and so on in the error handling after
> > host_init is finished.
> >
> > Signed-off-by: Richard Zhu <hongxing.zhu@xxxxxxx>
> > ---
> >  drivers/pci/controller/dwc/pci-imx6.c | 30
> > ++++++++++++++++++++++++---
> >  1 file changed, 27 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/pci/controller/dwc/pci-imx6.c
> > b/drivers/pci/controller/dwc/pci-imx6.c
> > index e165ad00989c..7a7d9204c6bc 100644
> > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > @@ -848,7 +848,9 @@ static int imx6_pcie_start_link(struct dw_pcie *pci)
> >         /* Start LTSSM. */
> >         imx6_pcie_ltssm_enable(dev);
> >
> > -       dw_pcie_wait_for_link(pci);
> > +       ret = dw_pcie_wait_for_link(pci);
> > +       if (ret)
> > +               goto err_reset_phy;
> >
> >         if (pci->link_gen == 2) {
> >                 /* Allow Gen2 mode after the link is up. */ @@ -884,7
> > +886,9 @@ static int imx6_pcie_start_link(struct dw_pcie *pci)
> >                 }
> >
> >                 /* Make sure link training is finished as well! */
> > -               dw_pcie_wait_for_link(pci);
> > +               ret = dw_pcie_wait_for_link(pci);
> > +               if (ret)
> > +                       goto err_reset_phy;
> >         } else {
> >                 dev_info(dev, "Link: Gen2 disabled\n");
> >         }
> > @@ -897,7 +901,6 @@ static int imx6_pcie_start_link(struct dw_pcie *pci)
> >         dev_dbg(dev, "PHY DEBUG_R0=0x%08x DEBUG_R1=0x%08x\n",
> >                 dw_pcie_readl_dbi(pci, PCIE_PORT_DEBUG0),
> >                 dw_pcie_readl_dbi(pci, PCIE_PORT_DEBUG1));
> > -       imx6_pcie_reset_phy(imx6_pcie);
> >         return ret;
> >  }
> >
> > @@ -921,8 +924,29 @@ static int imx6_pcie_host_init(struct pcie_port *pp)
> >         return 0;
> >  }
> >
> > +static void imx6_pcie_host_exit(struct pcie_port *pp) {
> > +       struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> > +       struct device *dev = pci->dev;
> > +       struct imx6_pcie *imx6_pcie = to_imx6_pcie(pci);
> > +
> > +       imx6_pcie_reset_phy(imx6_pcie);
> > +       imx6_pcie_clk_disable(imx6_pcie);
> > +       switch (imx6_pcie->drvdata->variant) {
> > +       case IMX8MM:
> > +               if (phy_power_off(imx6_pcie->phy))
> > +                       dev_err(dev, "unable to power off phy\n");
> > +               break;
> > +       default:
> > +               break;
> > +       }
> > +       if (imx6_pcie->vpcie)
> > +               regulator_disable(imx6_pcie->vpcie);
> > +}
> > +
> >  static const struct dw_pcie_host_ops imx6_pcie_host_ops = {
> >         .host_init = imx6_pcie_host_init,
> > +       .host_exit = imx6_pcie_host_exit,
> >  };
> >
> >  static const struct dw_pcie_ops dw_pcie_ops = {
> > --
> > 2.25.1
> >