linux-kernel - RE: [PATCH v1 1/5] PCI: imx6: Start link directly when workaround is not required

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Message-ID:
 <AS8PR04MB8676437B8097EE171631E6EB8CA42@AS8PR04MB8676.eurprd04.prod.outlook.com>
Date: Mon, 24 Mar 2025 07:48:02 +0000
From: Hongxing Zhu <hongxing.zhu@....com>
To: 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>, "manivannan.sadhasivam@...aro.org"
	<manivannan.sadhasivam@...aro.org>, "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>
CC: "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 v1 1/5] PCI: imx6: Start link directly when workaround is
 not required


> -----Original Message-----
> From: Hongxing Zhu <hongxing.zhu@....com>
> Sent: 2025年3月24日 14:27
> To: Frank Li <frank.li@....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
> Cc: linux-pci@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
> imx@...ts.linux.dev; linux-kernel@...r.kernel.org; Hongxing Zhu
> <hongxing.zhu@....com>
> Subject: [PATCH v1 1/5] PCI: imx6: Start link directly when workaround is not
> required
> 
> The current link setup procedure is more like one workaround to detect the
> device behind PCIe switches on some i.MX6 platforms.
> 
> To describe more accurately, change the flag name from
> IMX_PCIE_FLAG_IMX_SPEED_CHANGE to
> IMX_PCIE_FLAG_SPEED_CHANGE_WORKAROUND.
> 
> Then, start PCIe link directly when this flag is not set on i.MX7 or later
> paltforms to simple and speed up link training.
> 
> Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 34 +++++++++++----------------
>  1 file changed, 14 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c
> b/drivers/pci/controller/dwc/pci-imx6.c
> index c1f7904e3600..aa5c3f235995 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -91,7 +91,7 @@ enum imx_pcie_variants {  };
> 
>  #define IMX_PCIE_FLAG_IMX_PHY			BIT(0)
> -#define IMX_PCIE_FLAG_IMX_SPEED_CHANGE		BIT(1)
> +#define IMX_PCIE_FLAG_SPEED_CHANGE_WORDAROUND	BIT(1)
WORDAROUND/s/WORKAROUND
Sorry to find this typo error after patch-set is issued.
Would correct them all in next version.

Best Regards
Richard Zhu
>  #define IMX_PCIE_FLAG_SUPPORTS_SUSPEND		BIT(2)
>  #define IMX_PCIE_FLAG_HAS_PHYDRV		BIT(3)
>  #define IMX_PCIE_FLAG_HAS_APP_RESET		BIT(4)
> @@ -860,6 +860,12 @@ static int imx_pcie_start_link(struct dw_pcie *pci)
>  	u32 tmp;
>  	int ret;
> 
> +	if (!(imx_pcie->drvdata->flags &
> +	    IMX_PCIE_FLAG_SPEED_CHANGE_WORDAROUND)) {
> +		imx_pcie_ltssm_enable(dev);
> +		return 0;
> +	}
> +
>  	/*
>  	 * Force Gen1 operation when starting the link.  In case the link is
>  	 * started in Gen2 mode, there is a possibility the devices on the @@
> -896,22 +902,10 @@ static int imx_pcie_start_link(struct dw_pcie *pci)
>  		dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL,
> tmp);
>  		dw_pcie_dbi_ro_wr_dis(pci);
> 
> -		if (imx_pcie->drvdata->flags &
> -		    IMX_PCIE_FLAG_IMX_SPEED_CHANGE) {
> -
> -			/*
> -			 * On i.MX7, DIRECT_SPEED_CHANGE behaves differently
> -			 * from i.MX6 family when no link speed transition
> -			 * occurs and we go Gen1 -> yep, Gen1. The difference
> -			 * is that, in such case, it will not be cleared by HW
> -			 * which will cause the following code to report false
> -			 * failure.
> -			 */
> -			ret = imx_pcie_wait_for_speed_change(imx_pcie);
> -			if (ret) {
> -				dev_err(dev, "Failed to bring link up!\n");
> -				goto err_reset_phy;
> -			}
> +		ret = imx_pcie_wait_for_speed_change(imx_pcie);
> +		if (ret) {
> +			dev_err(dev, "Failed to bring link up!\n");
> +			goto err_reset_phy;
>  		}
> 
>  		/* Make sure link training is finished as well! */ @@ -1665,7
> +1659,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
>  	[IMX6Q] = {
>  		.variant = IMX6Q,
>  		.flags = IMX_PCIE_FLAG_IMX_PHY |
> -			 IMX_PCIE_FLAG_IMX_SPEED_CHANGE |
> +			 IMX_PCIE_FLAG_SPEED_CHANGE_WORDAROUND |
>  			 IMX_PCIE_FLAG_BROKEN_SUSPEND |
>  			 IMX_PCIE_FLAG_SUPPORTS_SUSPEND,
>  		.dbi_length = 0x200,
> @@ -1681,7 +1675,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
>  	[IMX6SX] = {
>  		.variant = IMX6SX,
>  		.flags = IMX_PCIE_FLAG_IMX_PHY |
> -			 IMX_PCIE_FLAG_IMX_SPEED_CHANGE |
> +			 IMX_PCIE_FLAG_SPEED_CHANGE_WORDAROUND |
>  			 IMX_PCIE_FLAG_SUPPORTS_SUSPEND,
>  		.gpr = "fsl,imx6q-iomuxc-gpr",
>  		.ltssm_off = IOMUXC_GPR12,
> @@ -1696,7 +1690,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
>  	[IMX6QP] = {
>  		.variant = IMX6QP,
>  		.flags = IMX_PCIE_FLAG_IMX_PHY |
> -			 IMX_PCIE_FLAG_IMX_SPEED_CHANGE |
> +			 IMX_PCIE_FLAG_SPEED_CHANGE_WORDAROUND |
>  			 IMX_PCIE_FLAG_SUPPORTS_SUSPEND,
>  		.dbi_length = 0x200,
>  		.gpr = "fsl,imx6q-iomuxc-gpr",
> --
> 2.37.1