linux-kernel - Re: [PATCH v2 1/2] PCI: imx6: Remove apps_reset toggle in _core

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Message-ID: <CAJ+vNU3vyznybZ_QZBrB+nc1=2+BcC8csOtR5=6-gmgn6sb5tQ@mail.gmail.com>
Date: Thu, 12 Jun 2025 12:47:52 -0700
From: Tim Harvey <tharvey@...eworks.com>
To: Frank Li <Frank.li@....com>
Cc: Richard Zhu <hongxing.zhu@....com>, l.stach@...gutronix.de, lpieralisi@...nel.org, 
	kw@...ux.com, manivannan.sadhasivam@...aro.org, robh@...nel.org, 
	bhelgaas@...gle.com, shawnguo@...nel.org, s.hauer@...gutronix.de, 
	kernel@...gutronix.de, festevam@...il.com, linux-pci@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, imx@...ts.linux.dev, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] PCI: imx6: Remove apps_reset toggle in _core_reset functions

On Thu, Jun 12, 2025 at 9:11 AM Frank Li <Frank.li@....com> wrote:
>
> On Thu, Jun 12, 2025 at 10:27:46AM +0800, Richard Zhu wrote:
> > apps_reset is LTSSM_EN on i.MX7, i.MX8MQ, i.MX8MM and i.MX8MP platforms.
> > Since the assertion/de-assertion of apps_reset(LTSSM_EN bit) had been
> > wrappered in imx_pcie_ltssm_enable() and imx_pcie_ltssm_disable();
> >
> > Remove apps_reset toggle in imx_pcie_assert_core_reset() and
> > imx_pcie_deassert_core_reset() functions. Use imx_pcie_ltssm_enable()
> > and imx_pcie_ltssm_disable() to configure apps_reset directly.
> >
> > Fix fail to enumerate reliably PI7C9X2G608GP (hotplug) at i.MX8MM, which
> > reported By Tim.
> >
>
> You may rename apps_reset to ltssm_reset to avoid confuse for legancy
> platform later.

Hi Frank and Richard,

I was thinking of making the same suggestion however the apps reset is
in several places:
- imx8m*.dtsi pci node as 'reset-names' and reset index number #define
- imx8m*-reset.h bindings as reset index number/define
- pci-imx.c driver

Granted it is used by imx7d.dtsi, fsl,imx8mq-pcie, fsl,imx8mm-pcie,
fsl,imx8mp-pcie and in every one of those reference manuals it's bit6
of SRC_PCIEPH_RCR named PCIE_CTRL_APPS_EN but described as
'Pcie_ctrl_app_ltssm_enable'. Can you ask your references to get more
definition for this bit? I'm still unclear why 'de-asserting' it twice
was an issue.

Regardless, any cleanup changing the name can be a seperate patch in my opinion.

Best Regards,

Tim


>
> Reviewed-by: Frank Li <Frank.Li@....com>
>
>
> > Reported-by: Tim Harvey <tharvey@...eworks.com>
> > Closes: https://lore.kernel.org/all/CAJ+vNU3ohR2YKTwC4xoYrc1z-neDoH2TTZcMHDy+poj9=jSy+w@mail.gmail.com/
> > Fixes: ef61c7d8d032 ("PCI: imx6: Deassert apps_reset in imx_pcie_deassert_core_reset()")
> > Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> > ---
> >  drivers/pci/controller/dwc/pci-imx6.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> > index 5f267dd261b5..f4e0342f4d56 100644
> > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > @@ -776,7 +776,6 @@ static int imx7d_pcie_core_reset(struct imx_pcie *imx_pcie, bool assert)
> >  static void imx_pcie_assert_core_reset(struct imx_pcie *imx_pcie)
> >  {
> >       reset_control_assert(imx_pcie->pciephy_reset);
> > -     reset_control_assert(imx_pcie->apps_reset);
> >
> >       if (imx_pcie->drvdata->core_reset)
> >               imx_pcie->drvdata->core_reset(imx_pcie, true);
> > @@ -788,7 +787,6 @@ static void imx_pcie_assert_core_reset(struct imx_pcie *imx_pcie)
> >  static int imx_pcie_deassert_core_reset(struct imx_pcie *imx_pcie)
> >  {
> >       reset_control_deassert(imx_pcie->pciephy_reset);
> > -     reset_control_deassert(imx_pcie->apps_reset);
> >
> >       if (imx_pcie->drvdata->core_reset)
> >               imx_pcie->drvdata->core_reset(imx_pcie, false);
> > @@ -1176,6 +1174,9 @@ static int imx_pcie_host_init(struct dw_pcie_rp *pp)
> >               }
> >       }
> >
> > +     /* Make sure that PCIe LTSSM is cleared */
> > +     imx_pcie_ltssm_disable(dev);
> > +
> >       ret = imx_pcie_deassert_core_reset(imx_pcie);
> >       if (ret < 0) {
> >               dev_err(dev, "pcie deassert core reset failed: %d\n", ret);
> > --
> > 2.37.1
> >