linux-kernel - Re: [PATCH v2 05/11] PCI: mvebu: Correctly configure x1/x4 mode

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Message-ID: <YemXPQx4F1eRtLxO@robh.at.kernel.org>
Date:   Thu, 20 Jan 2022 11:09:17 -0600
From:   Rob Herring <robh@...nel.org>
To:     Pali Rohár <pali@...nel.org>
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Marek Behún <kabel@...nel.org>,
        Russell King <rmk+kernel@...linux.org.uk>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 05/11] PCI: mvebu: Correctly configure x1/x4 mode

On Wed, Jan 12, 2022 at 04:18:08PM +0100, Pali Rohár wrote:
> If x1/x4 mode is not set correctly then link with endpoint card is not
> established.
> 
> Use DTS property 'num-lanes' to deteriminate x1/x4 mode.
> 
> Signed-off-by: Pali Rohár <pali@...nel.org>
> ---
>  drivers/pci/controller/pci-mvebu.c | 19 ++++++++++++++++++-
>  1 file changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/pci-mvebu.c b/drivers/pci/controller/pci-mvebu.c
> index a075ba26cff1..0f2ec0a17874 100644
> --- a/drivers/pci/controller/pci-mvebu.c
> +++ b/drivers/pci/controller/pci-mvebu.c
> @@ -93,6 +93,7 @@ struct mvebu_pcie_port {
>  	void __iomem *base;
>  	u32 port;
>  	u32 lane;
> +	bool is_x4;

I would just store the number of lanes.

>  	int devfn;
>  	unsigned int mem_target;
>  	unsigned int mem_attr;
> @@ -233,13 +234,25 @@ static void mvebu_pcie_setup_wins(struct mvebu_pcie_port *port)
>  
>  static void mvebu_pcie_setup_hw(struct mvebu_pcie_port *port)
>  {
> -	u32 ctrl, cmd, dev_rev, mask;
> +	u32 ctrl, lnkcap, cmd, dev_rev, mask;
>  
>  	/* Setup PCIe controller to Root Complex mode. */
>  	ctrl = mvebu_readl(port, PCIE_CTRL_OFF);
>  	ctrl |= PCIE_CTRL_RC_MODE;
>  	mvebu_writel(port, ctrl, PCIE_CTRL_OFF);
>  
> +	/*
> +	 * Set Maximum Link Width to X1 or X4 in Root Port's PCIe Link
> +	 * Capability register. This register is defined by PCIe specification
> +	 * as read-only but this mvebu controller has it as read-write and must
> +	 * be set to number of SerDes PCIe lanes (1 or 4). If this register is
> +	 * not set correctly then link with endpoint card is not established.
> +	 */
> +	lnkcap = mvebu_readl(port, PCIE_CAP_PCIEXP + PCI_EXP_LNKCAP);
> +	lnkcap &= ~PCI_EXP_LNKCAP_MLW;
> +	lnkcap |= (port->is_x4 ? 4 : 1) << 4;

then this is just: lanes << 4

> +	mvebu_writel(port, lnkcap, PCIE_CAP_PCIEXP + PCI_EXP_LNKCAP);
> +
>  	/* Disable Root Bridge I/O space, memory space and bus mastering. */
>  	cmd = mvebu_readl(port, PCIE_CMD_OFF);
>  	cmd &= ~(PCI_COMMAND_IO | PCI_COMMAND_MEMORY | PCI_COMMAND_MASTER);
> @@ -986,6 +999,7 @@ static int mvebu_pcie_parse_port(struct mvebu_pcie *pcie,
>  	struct device *dev = &pcie->pdev->dev;
>  	enum of_gpio_flags flags;
>  	int reset_gpio, ret;
> +	u32 num_lanes;
>  
>  	port->pcie = pcie;
>  
> @@ -998,6 +1012,9 @@ static int mvebu_pcie_parse_port(struct mvebu_pcie *pcie,
>  	if (of_property_read_u32(child, "marvell,pcie-lane", &port->lane))
>  		port->lane = 0;
>  
> +	if (!of_property_read_u32(child, "num-lanes", &num_lanes) && num_lanes == 4)
> +		port->is_x4 = true;

And this can be:

num_lanes = 1;
of_property_read_u32(child, "num-lanes", &num_lanes);

If you want to validate the DT is only 1 or 4, make the DT schema do 
that.


> +
>  	port->name = devm_kasprintf(dev, GFP_KERNEL, "pcie%d.%d", port->port,
>  				    port->lane);
>  	if (!port->name) {
> -- 
> 2.20.1
> 
>