linux-kernel - Re: [RFC 1/2] PCI: imx6: Make sure the DBI register can be changed

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Date:   Mon, 11 Jul 2022 17:17:01 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Richard Zhu <hongxing.zhu@....com>
Cc:     l.stach@...gutronix.de, bhelgaas@...gle.com,
        lorenzo.pieralisi@....com, festevam@...il.com,
        linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, kernel@...gutronix.de,
        linux-imx@....com
Subject: Re: [RFC 1/2] PCI: imx6: Make sure the DBI register can be changed

Hi Richard,

On Wed, May 18, 2022 at 05:35:27PM +0800, Richard Zhu wrote:
> The PCIE_DBI_RO_WR_EN bit should be set when write some DBI registers.
> To make sure that the DBI registers are writable, set the
> PCIE_DBI_RO_WR_EN properly when touch the DBI registers.
> 
> Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 6619e3caffe2..30641d2dda14 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -797,10 +797,12 @@ static int imx6_pcie_start_link(struct dw_pcie *pci)
>  	 * started in Gen2 mode, there is a possibility the devices on the
>  	 * bus will not be detected at all.  This happens with PCIe switches.
>  	 */
> +	dw_pcie_dbi_ro_wr_en(pci);

What's the status of this patch?  I don't see this change included in
your v14 series [1].  That series has a lot of imx6 updates, so I
would have thought you'd include this change in it.  Or maybe this
change turned out not to be needed?

What about the 2/2 patch?

They're both marked "RFC" which is sometimes a hint that the author
isn't really committed to the patch, so sometimes they don't get the
attention they deserve.

Bjorn

[1] https://lore.kernel.org/r/1656645935-1370-1-git-send-email-hongxing.zhu@nxp.com

>  	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_dbi_ro_wr_dis(pci);
>  
>  	/* Start LTSSM. */
>  	imx6_pcie_ltssm_enable(dev);
> @@ -809,6 +811,7 @@ static int imx6_pcie_start_link(struct dw_pcie *pci)
>  
>  	if (pci->link_gen == 2) {
>  		/* Allow Gen2 mode 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_EXP_LNKCAP_SLS_5_0GB;
> @@ -821,6 +824,7 @@ static int imx6_pcie_start_link(struct dw_pcie *pci)
>  		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_dbi_ro_wr_dis(pci);
>  
>  		if (imx6_pcie->drvdata->flags &
>  		    IMX6_PCIE_FLAG_IMX6_SPEED_CHANGE) {
> -- 
> 2.25.1
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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