linux-kernel - Re: [PATCH v3 1/2] PCI: imx6: Remove apps_reset toggle in _core

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Message-ID: <kjsaipr2xq777dmiv2ac7qzrxw47nevc75j7ryma32vsnyr2le@mrwurn6rgnac>
Date: Mon, 23 Jun 2025 05:42:50 -0600
From: Manivannan Sadhasivam <mani@...nel.org>
To: Richard Zhu <hongxing.zhu@....com>
Cc: frank.li@....com, l.stach@...gutronix.de, lpieralisi@...nel.org, 
	kwilczynski@...nel.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, Tim Harvey <tharvey@...eworks.com>
Subject: Re: [PATCH v3 1/2] PCI: imx6: Remove apps_reset toggle in
 _core_reset functions

On Mon, Jun 16, 2025 at 04:57:41PM +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();
> 

What about other i.MX chipsets like 6Q and its cousins? Wouldn't this change
affect them since they treat 'apps_reset' differently?

- Mani

> 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@...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>
> Reviewed-by: Frank Li <Frank.Li@....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 9754cc6e09b9..f5f2ac638f4b 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -860,7 +860,6 @@ static int imx95_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);
> @@ -872,7 +871,6 @@ 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);
> @@ -1247,6 +1245,9 @@ 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
> 

-- 
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