From: Hongxing Zhu <hongxing.zhu@nxp.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: "l.stach@pengutronix.de" <l.stach@pengutronix.de>,
"bhelgaas@google.com" <bhelgaas@google.com>,
"lorenzo.pieralisi@arm.com" <lorenzo.pieralisi@arm.com>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kernel@pengutronix.de" <kernel@pengutronix.de>,
dl-linux-imx <linux-imx@nxp.com>
Subject: RE: [PATCH] PCI: imx6: Override the CLKREQ low in the initialization
Date: Thu, 24 Feb 2022 02:04:25 +0000 [thread overview]
Message-ID: <AS8PR04MB8676FFAEF40286DC979FBEAC8C3D9@AS8PR04MB8676.eurprd04.prod.outlook.com> (raw)
In-Reply-To: <20220223183157.GA142509@bhelgaas>
> -----Original Message-----
> From: Bjorn Helgaas <helgaas@kernel.org>
> Sent: 2022年2月24日 2:32
> To: Hongxing Zhu <hongxing.zhu@nxp.com>
> Cc: l.stach@pengutronix.de; bhelgaas@google.com;
> lorenzo.pieralisi@arm.com; linux-pci@vger.kernel.org;
> linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org;
> kernel@pengutronix.de; dl-linux-imx <linux-imx@nxp.com>
> Subject: Re: [PATCH] PCI: imx6: Override the CLKREQ low in the initialization
>
> In subject, maybe:
>
> PCI: imx6: Assert i.MX8MM CLKREQ# even if no device present
>
> On Wed, Feb 23, 2022 at 04:38:33PM +0800, Richard Zhu wrote:
> > The CLKREQ# signal is an open drain, active low signal that is driven
> > low by the remote Endpoint device. But it might not be driven low if
> > no Endpoint device is connected.
> >
> > On i.MX8MM PCIe, phy_init() would be failed and system boot hang if
> > the reference clock is not toggled.
>
> s/would be failed/may fail/
> s/boot hang/boot may hang/
> s/if the reference clock is not toggled/if no Endpoint is connected to assert
> CLKREQ#/
>
> > Follow with i.MX8MQ PCIe, to make sure the reference clock on,
> > override the CLKREQ# low during initialization to fix this issue.
>
> Handle this as on i.MX8MQ, where we explicitly assert CLKREQ# so the
> PHY can be initialized.
>
> (I don't really understand the hardware here, so disregard if this doesn't say
> what it needs to.)
Hi Bjorn:
Thanks a lot.
Your description is much better than mine.
Would be changed later.
Best Regards
Richard Zhu
>
> > Fixes: 178e244cb6e2 ("PCI: imx: Add the imx8mm pcie support")
> > Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
> > ---
> > drivers/pci/controller/dwc/pci-imx6.c | 4 ----
> > 1 file changed, 4 deletions(-)
> >
> > diff --git a/drivers/pci/controller/dwc/pci-imx6.c
> > b/drivers/pci/controller/dwc/pci-imx6.c
> > index d7f0db01f3c3..a334341a1789 100644
> > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > @@ -447,10 +447,6 @@ static int imx6_pcie_enable_ref_clk(struct
> imx6_pcie *imx6_pcie)
> > case IMX7D:
> > break;
> > case IMX8MM:
> > - ret = clk_prepare_enable(imx6_pcie->pcie_aux);
> > - if (ret)
> > - dev_err(dev, "unable to enable pcie_aux clock\n");
> > - break;
> > case IMX8MQ:
> > ret = clk_prepare_enable(imx6_pcie->pcie_aux);
> > if (ret) {
> > --
> > 2.25.1
> >
prev parent reply other threads:[~2022-02-24 2:04 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-23 8:38 [PATCH] PCI: imx6: Override the CLKREQ low in the initialization Richard Zhu
2022-02-23 18:31 ` Bjorn Helgaas
2022-02-24 2:04 ` Hongxing Zhu [this message]
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