linux-kernel - Re: [PATCH v5 6/7] PCI: imx6: Add PLL clock lock check for i.MX95 PCIe

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Message-ID: <3wmkjmutepc2s2ookc3ces4eyxe6morhhwxzlpup4mkkoy5ocx@py6h36upgl75>
Date: Tue, 15 Apr 2025 12:50:53 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Hongxing Zhu <hongxing.zhu@....com>
Cc: Frank Li <frank.li@....com>, 
	"l.stach@...gutronix.de" <l.stach@...gutronix.de>, "lpieralisi@...nel.org" <lpieralisi@...nel.org>, 
	"kw@...ux.com" <kw@...ux.com>, "robh@...nel.org" <robh@...nel.org>, 
	"bhelgaas@...gle.com" <bhelgaas@...gle.com>, "shawnguo@...nel.org" <shawnguo@...nel.org>, 
	"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>, "kernel@...gutronix.de" <kernel@...gutronix.de>, 
	"festevam@...il.com" <festevam@...il.com>, "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>, 
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "imx@...ts.linux.dev" <imx@...ts.linux.dev>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 6/7] PCI: imx6: Add PLL clock lock check for i.MX95
 PCIe

On Mon, Apr 14, 2025 at 03:16:46AM +0000, Hongxing Zhu wrote:
> > -----Original Message-----
> > From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > Sent: 2025年4月13日 23:33
> > To: Hongxing Zhu <hongxing.zhu@....com>
> > Cc: Frank Li <frank.li@....com>; l.stach@...gutronix.de;
> > lpieralisi@...nel.org; kw@...ux.com; 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 v5 6/7] PCI: imx6: Add PLL clock lock check for i.MX95
> > PCIe
> > 
> > On Tue, Apr 08, 2025 at 10:59:29AM +0800, Richard Zhu wrote:
> > > Add PLL clock lock check for i.MX95 PCIe.
> > >
> > > Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> > > Reviewed-by: Frank Li <Frank.Li@....com>
> > > ---
> > >  drivers/pci/controller/dwc/pci-imx6.c | 28
> > > +++++++++++++++++++++++++--
> > >  1 file changed, 26 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/pci/controller/dwc/pci-imx6.c
> > > b/drivers/pci/controller/dwc/pci-imx6.c
> > > index 7dcc9d88740d..c1d128ec255d 100644
> > > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > > @@ -45,6 +45,9 @@
> > >  #define IMX95_PCIE_PHY_GEN_CTRL			0x0
> > >  #define IMX95_PCIE_REF_USE_PAD			BIT(17)
> > >
> > > +#define IMX95_PCIE_PHY_MPLLA_CTRL		0x10
> > > +#define IMX95_PCIE_PHY_MPLL_STATE		BIT(30)
> > > +
> > >  #define IMX95_PCIE_SS_RW_REG_0			0xf0
> > >  #define IMX95_PCIE_REF_CLKEN			BIT(23)
> > >  #define IMX95_PCIE_PHY_CR_PARA_SEL		BIT(9)
> > > @@ -479,6 +482,23 @@ static void
> > imx7d_pcie_wait_for_phy_pll_lock(struct imx_pcie *imx_pcie)
> > >  		dev_err(dev, "PCIe PLL lock timeout\n");  }
> > >
> > > +static int imx95_pcie_wait_for_phy_pll_lock(struct imx_pcie
> > > +*imx_pcie) {
> > > +	u32 val;
> > > +	struct device *dev = imx_pcie->pci->dev;
> > > +
> > > +	if (regmap_read_poll_timeout(imx_pcie->iomuxc_gpr,
> > > +				     IMX95_PCIE_PHY_MPLLA_CTRL, val,
> > > +				     val & IMX95_PCIE_PHY_MPLL_STATE,
> > > +				     PHY_PLL_LOCK_WAIT_USLEEP_MAX,
> > > +				     PHY_PLL_LOCK_WAIT_TIMEOUT)) {
> > > +		dev_err(dev, "PCIe PLL lock timeout\n");
> > > +		return -ETIMEDOUT;
> > > +	}
> > > +
> > > +	return 0;
> > > +}
> > > +
> > >  static int imx_setup_phy_mpll(struct imx_pcie *imx_pcie)  {
> > >  	unsigned long phy_rate = 0;
> > > @@ -824,6 +844,8 @@ static int imx95_pcie_core_reset(struct imx_pcie
> > *imx_pcie, bool assert)
> > >  		regmap_read_bypassed(imx_pcie->iomuxc_gpr,
> > IMX95_PCIE_RST_CTRL,
> > >  				     &val);
> > >  		udelay(10);
> > > +	} else {
> > > +		return imx95_pcie_wait_for_phy_pll_lock(imx_pcie);
> > 
> > Is this PLL lock related to COLD_RESET? It doesn't look like it. If unrelated, it
> > should be called wherever required. imx95_pcie_core_reset() is supposed to
> > only assert/deassert the COLD_RESET.
> > 
> > If related, please explain how.
> Thanks for your kindly review.
> To make sure the HW state is correct to continue the sequential initializations.
> The PLL lock or not check would be kicked off after the COLD_RESET is
>  de-asserted for i.MX95 PCIe.
> So, the PLL lock check is added at the end of de-assertion in
>  imx95_pcie_core_reset() function.
> 

But imx95_pcie_core_reset() is not doing anything for deassert other than
waiting for PLL lock. Hence my question.

- Mani

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