linux-kernel - Re: [PATCH 04/13] PCI: dwc: Refactor imx6 to use dw_pcie_clear_and_set

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Message-ID: <aEnNFgv08BVVxfOQ@lizhi-Precision-Tower-5810>
Date: Wed, 11 Jun 2025 14:38:14 -0400
From: Frank Li <Frank.li@....com>
To: Hans Zhang <18255117159@....com>
Cc: lpieralisi@...nel.org, bhelgaas@...gle.com, mani@...nel.org,
	kwilczynski@...nel.org, robh@...nel.org, jingoohan1@...il.com,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/13] PCI: dwc: Refactor imx6 to use
 dw_pcie_clear_and_set_dword()

On Thu, Jun 12, 2025 at 12:31:21AM +0800, Hans Zhang wrote:

Subject should be

PCI: dwc: imx6: Refactor code by using dw_pcie_clear_and_set_dword()

tag "imx6:" should after "dwc:"

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

> i.MX6 PCIe driver contains multiple read-modify-write sequences for
> link training and speed configuration. These operations manually handle
> bit masking and shifting to update specific fields in control registers,
> particularly for link capabilities and speed change initiation.
>
> Refactor link capability configuration and speed change handling using
> dw_pcie_clear_and_set_dword(). The helper simplifies LNKCAP modification
> by encapsulating bit clear/set operations and eliminates intermediate
> variables. For speed change control, replace explicit bit manipulation
> with direct register updates through the helper.
>
> Adopting the standard interface reduces code complexity in link training
> paths and ensures consistent handling of speed-related bits. The change
> also prepares the driver for future enhancements to Gen3 link training
> by centralizing bit manipulation logic.
>
> Signed-off-by: Hans Zhang <18255117159@....com>
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 26 ++++++++++----------------
>  1 file changed, 10 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 5a38cfaf989b..3004e432f013 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -941,7 +941,6 @@ static int imx_pcie_start_link(struct dw_pcie *pci)
>  	struct imx_pcie *imx_pcie = to_imx_pcie(pci);
>  	struct device *dev = pci->dev;
>  	u8 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> -	u32 tmp;
>  	int ret;
>
>  	if (!(imx_pcie->drvdata->flags &
> @@ -956,10 +955,9 @@ static int imx_pcie_start_link(struct dw_pcie *pci)
>  	 * bus will not be detected at all.  This happens with PCIe switches.
>  	 */
>  	dw_pcie_dbi_ro_wr_en(pci);
> -	tmp = dw_pcie_readl_dbi(pci, offset + PCI_EXP_LNKCAP);
> -	tmp &= ~PCI_EXP_LNKCAP_SLS;
> -	tmp |= PCI_EXP_LNKCAP_SLS_2_5GB;
> -	dw_pcie_writel_dbi(pci, offset + PCI_EXP_LNKCAP, tmp);
> +	dw_pcie_clear_and_set_dword(pci, offset + PCI_EXP_LNKCAP,
> +				    PCI_EXP_LNKCAP_SLS,
> +				    PCI_EXP_LNKCAP_SLS_2_5GB);
>  	dw_pcie_dbi_ro_wr_dis(pci);
>
>  	/* Start LTSSM. */
> @@ -972,18 +970,16 @@ static int imx_pcie_start_link(struct dw_pcie *pci)
>
>  		/* Allow faster modes after the link is up */
>  		dw_pcie_dbi_ro_wr_en(pci);
> -		tmp = dw_pcie_readl_dbi(pci, offset + PCI_EXP_LNKCAP);
> -		tmp &= ~PCI_EXP_LNKCAP_SLS;
> -		tmp |= pci->max_link_speed;
> -		dw_pcie_writel_dbi(pci, offset + PCI_EXP_LNKCAP, tmp);
> +		dw_pcie_clear_and_set_dword(pci, offset + PCI_EXP_LNKCAP,
> +					    PCI_EXP_LNKCAP_SLS,
> +					    pci->max_link_speed);
>
>  		/*
>  		 * Start Directed Speed Change so the best possible
>  		 * speed both link partners support can be negotiated.
>  		 */
> -		tmp = dw_pcie_readl_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL);
> -		tmp |= PORT_LOGIC_SPEED_CHANGE;
> -		dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, tmp);
> +		dw_pcie_clear_and_set_dword(pci, PCIE_LINK_WIDTH_SPEED_CONTROL,
> +					    0, PORT_LOGIC_SPEED_CHANGE);
>  		dw_pcie_dbi_ro_wr_dis(pci);
>
>  		ret = imx_pcie_wait_for_speed_change(imx_pcie);
> @@ -1295,7 +1291,6 @@ static void imx_pcie_host_post_init(struct dw_pcie_rp *pp)
>  {
>  	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
>  	struct imx_pcie *imx_pcie = to_imx_pcie(pci);
> -	u32 val;
>
>  	if (imx_pcie->drvdata->flags & IMX_PCIE_FLAG_8GT_ECN_ERR051586) {
>  		/*
> @@ -1310,9 +1305,8 @@ static void imx_pcie_host_post_init(struct dw_pcie_rp *pp)
>  		 * to 0.
>  		 */
>  		dw_pcie_dbi_ro_wr_en(pci);
> -		val = dw_pcie_readl_dbi(pci, GEN3_RELATED_OFF);
> -		val &= ~GEN3_RELATED_OFF_GEN3_ZRXDC_NONCOMPL;
> -		dw_pcie_writel_dbi(pci, GEN3_RELATED_OFF, val);
> +		dw_pcie_clear_and_set_dword(pci, GEN3_RELATED_OFF,
> +					    GEN3_RELATED_OFF_GEN3_ZRXDC_NONCOMPL, 0);
>  		dw_pcie_dbi_ro_wr_dis(pci);
>  	}
>  }
> --
> 2.25.1
>