[PATCH v2 0/2] PCI: imx6: Refine apps_reset and EP link behavior

[PATCH v2 0/2] PCI: imx6: Refine apps_reset and EP link behavior

[Richard Zhu]

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[1] to enumerate reliably PI7C9X2G608GP (hotplug) at i.MX8MM,
which reported By Tim.

Main changes in v2:
- Respin "PCI: imx6: Align EP link start behavior with" patch.
- Add the apps_reset refine patch into this patch-set.

[1]https://lore.kernel.org/all/CAJ+vNU3ohR2YKTwC4xoYrc1z-neDoH2TTZcMHDy+poj9=jSy+w@mail.gmail.com/

[PATCH v2 1/2] PCI: imx6: Remove apps_reset toggle in _core_reset
[PATCH v2 2/2] PCI: imx6: Align EP link start behavior with

drivers/pci/controller/dwc/pci-imx6.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)

[PATCH v2 1/2] PCI: imx6: Remove apps_reset toggle in _core_reset functions

[Richard Zhu]

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.

Reported-by: Tim Harvey <tharvey@gateworks.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@nxp.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

[PATCH v2 2/2] PCI: imx6: Align EP link start behavior with documentation

[Richard Zhu]

According to PCI/endpoint/pci-endpoint-cfs.rst, the endpoint (EP) should
only link up after `echo 1 > start` is executed.

To match the documented behavior, do not start the link automatically
when adding the EP controller.

Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
---
 drivers/pci/controller/dwc/pci-imx6.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index f4e0342f4d56..668b88bb7c95 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -1361,9 +1361,6 @@ static int imx_add_pcie_ep(struct imx_pcie *imx_pcie,
 
 	pci_epc_init_notify(ep->epc);
 
-	/* Start LTSSM. */
-	imx_pcie_ltssm_enable(dev);
-
 	return 0;
 }
 
-- 
2.37.1

Re: [PATCH v2 1/2] PCI: imx6: Remove apps_reset toggle in _core_reset functions

[Frank Li]

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.

Reviewed-by: Frank Li <Frank.Li@nxp.com>


> Reported-by: Tim Harvey <tharvey@gateworks.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@nxp.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
>

Re: [PATCH v2 1/2] PCI: imx6: Remove apps_reset toggle in _core_reset functions

[Tim Harvey]

On Thu, Jun 12, 2025 at 9:11 AM Frank Li <Frank.li@nxp.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@nxp.com>
>
>
> > Reported-by: Tim Harvey <tharvey@gateworks.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@nxp.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
> >

RE: [PATCH v2 1/2] PCI: imx6: Remove apps_reset toggle in _core_reset functions

[Hongxing Zhu]

> -----Original Message-----
> From: Tim Harvey <tharvey@gateworks.com>
> Sent: 2025年6月13日 3:48
> To: Frank Li <frank.li@nxp.com>
> Cc: Hongxing Zhu <hongxing.zhu@nxp.com>; l.stach@pengutronix.de;
> lpieralisi@kernel.org; kw@linux.com; manivannan.sadhasivam@linaro.org;
> robh@kernel.org; bhelgaas@google.com; shawnguo@kernel.org;
> s.hauer@pengutronix.de; kernel@pengutronix.de; festevam@gmail.com;
> linux-pci@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
> imx@lists.linux.dev; linux-kernel@vger.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@nxp.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.
I suspect that the link had been abnormal already before 'de-asserting'
 the ltssm_en bit at twice time. The regmap_read() trigger the hang in
 your use case actually.

Best Regards
Richard Zhu
> 
> Regardless, any cleanup changing the name can be a seperate patch in my
> opinion.
> 
> Best Regards,
> 
> Tim
> 
> 
> >
> > Reviewed-by: Frank Li <Frank.Li@nxp.com>
> >
> >
> > > Reported-by: Tim Harvey <tharvey@gateworks.com>
> > > Closes:
> > > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flo
> > >
> re.kernel.org%2Fall%2FCAJ%2BvNU3ohR2YKTwC4xoYrc1z-neDoH2TTZcMHDy%
> 2Bp
> > >
> oj9%3DjSy%2Bw%40mail.gmail.com%2F&data=05%7C02%7Chongxing.zhu%40
> nxp.
> > >
> com%7C3d1b3ffa38ef4038063a08dda9ea0c63%7C686ea1d3bc2b4c6fa92cd99c
> 5c3
> > >
> 01635%7C0%7C0%7C638853544881671954%7CUnknown%7CTWFpbGZsb3d8e
> yJFbXB0e
> > >
> U1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsI
> > >
> ldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=7vV5HyEaluYf4i4l2anEX%2Fb6z3x
> UPc0
> > > urhHNIdTPKwU%3D&reserved=0
> > > Fixes: ef61c7d8d032 ("PCI: imx6: Deassert apps_reset in
> > > imx_pcie_deassert_core_reset()")
> > > Signed-off-by: Richard Zhu <hongxing.zhu@nxp.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
> > >