Re: [PATCH 04/13] PCI: dwc: Refactor imx6 to use dw_pcie_clear_and_set_dword()

[Hans Zhang]

On 2025/6/12 02:43, Frank Li wrote:
> On Thu, Jun 12, 2025 at 12:31:21AM +0800, Hans Zhang wrote:
> > 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.
>
> Sorry, where define dw_pcie_clear_and_set_dword() ?

Dear Frank,

Thank you very much for your reply.

Please see the following link:
https://patchwork.kernel.org/project/linux-pci/patch/20250611163057.860353-1-18255117159@xxxxxxx/

Best regards,
Hans

> > Signed-off-by: Hans Zhang <18255117159@xxxxxxx>
> > ---
> >   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);
>
> supposed 3 args is mask. 0 should be PORT_LOGIC_SPEED_CHANGE.
>
> Frank
>
> >   		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