Re: [PATCH] phy: fsl-imx8mq-usb: add debugfs to access control register

Vinod Koul
2025-12-23T14:19:15Z

On 19-12-25, 15:54, Xu Yang wrote:
> The CR port is a simple 16-bit data/address parallel port that is
> provided for on-chip access to the control registers inside the
> USB 3.0 femtoPHY. While access to these registers is not required
> for normal PHY operation, this interface enables you to access
> some of the PHY’s diagnostic features during normal operation or
> to override some basic PHY control signals.
>
> 3 debugfs files are created to read and write control registers,
> all use hexadecimal format:
> ctrl_reg_base: the register offset to write, or the start offset
> to read.
> ctrl_reg_count: how many continuous registers to be read.
> ctrl_reg_value: read to show the continuous registers value from
> the offset in ctrl_reg_base, to ctrl_reg_base
> + ctrl_reg_count - 1, one line for one register.
> when write, override the register at ctrl_reg_base,
> one time can only change one 16bits register.
>
> Signed-off-by: Li Jun <jun.li@nxp.com>
> Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
> ---
> drivers/phy/freescale/phy-fsl-imx8mq-usb.c | 221 ++++++++++++++++++++-
> 1 file changed, 220 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/phy/freescale/phy-fsl-imx8mq-usb.c b/drivers/phy/freescale/phy-fsl-imx8mq-usb.c
> index ad8a55012e42..cb2392008ad2 100644
> --- a/drivers/phy/freescale/phy-fsl-imx8mq-usb.c
> +++ b/drivers/phy/freescale/phy-fsl-imx8mq-usb.c
> @@ -1,8 +1,9 @@
> // SPDX-License-Identifier: GPL-2.0+
> -/* Copyright (c) 2017 NXP. */
> +/* Copyright (c) 2017-2025 NXP. */
>
> #include <linux/bitfield.h>
> #include <linux/clk.h>
> +#include <linux/debugfs.h>
> #include <linux/delay.h>
> #include <linux/io.h>
> #include <linux/module.h>
> @@ -52,6 +53,21 @@
>
> #define PHY_TUNE_DEFAULT 0xffffffff
>
> +/* PHY control register access */
> +#define PHY_CTRL_REG_COUNT_MAX 0x42
> +#define PHY_CTRL_REG_OFFSET_MAX 0x201f
> +
> +#define PHY_CRCTL 0x30
> +#define PHY_CRCTL_DATA_IN_MASK GENMASK(15, 0)
> +#define PHY_CRCTL_CAP_ADDR BIT(16)
> +#define PHY_CRCTL_CAP_DATA BIT(17)
> +#define PHY_CRCTL_CR_WRITE BIT(18)
> +#define PHY_CRCTL_CR_READ BIT(19)
> +
> +#define PHY_CRSR 0x34
> +#define PHY_CRSR_DATA_OUT_MASK GENMASK(15, 0)
> +#define PHY_CRSR_CR_ACK BIT(16)
> +
> #define TCA_CLK_RST 0x00
> #define TCA_CLK_RST_SW BIT(9)
> #define TCA_CLK_RST_REF_CLK_EN BIT(1)
> @@ -113,6 +129,9 @@ struct imx8mq_usb_phy {
> void __iomem *base;
> struct regulator *vbus;
> struct tca_blk *tca;
> + struct dentry *debugfs;
> + u16 cr_access_base;
> + u16 cr_read_count;
> u32 pcs_tx_swing_full;
> u32 pcs_tx_deemph_3p5db;
> u32 tx_vref_tune;
> @@ -420,6 +439,204 @@ static u32 phy_pcs_tx_swing_full_from_property(u32 percent)
> percent = min(percent, 100U);
>
> return (percent * 127) / 100;
> +};
> +
> +#define IMX8M_PHY_DEBUG_PORT_LOOP_TIMEOUT 500000

empty line here, possibly move this to top of file

> +static int imx8mq_phy_ctrl_reg_addr(struct imx8mq_usb_phy *imx_phy, u16 offset)
> +{
> + void __iomem *cr_ctrl = imx_phy->base + PHY_CRCTL;
> + void __iomem *cr_sr = imx_phy->base + PHY_CRSR;
> + struct device *dev = &imx_phy->phy->dev;
> + int i;
> +
> + /* Address Phrase */
> + writel(offset, cr_ctrl);
> + writel(readl(cr_ctrl) | PHY_CRCTL_CAP_ADDR, cr_ctrl);
> +
> + /* Wait CRSR[16] == 1 */
> + i = IMX8M_PHY_DEBUG_PORT_LOOP_TIMEOUT;
> + while (!(readl(cr_sr) & PHY_CRSR_CR_ACK) && i > 0)
> + i--;
> + if (i == 0)
> + goto cr_addr_err;
> +
> + writel(readl(cr_ctrl) & (~PHY_CRCTL_CAP_ADDR), cr_ctrl);
> +
> + /* Wait CRSR[16] == 0 */
> + i = IMX8M_PHY_DEBUG_PORT_LOOP_TIMEOUT;
> + while ((readl(cr_sr) & PHY_CRSR_CR_ACK) && i > 0)
> + i--;
> + if (i == 0)
> + goto cr_addr_err;
> +
> + return 0;
> +
> +cr_addr_err:
> + dev_err(dev, "Failed to address reg 0x%x.\n", offset);
> + return -EIO;
> +}
> +
> +static int imx8mq_phy_ctrl_reg_read(struct imx8mq_usb_phy *imx_phy, u16 offset)
> +{
> + void __iomem *cr_ctrl = imx_phy->base + PHY_CRCTL;
> + void __iomem *cr_sr = imx_phy->base + PHY_CRSR;
> + struct device *dev = &imx_phy->phy->dev;
> + int val, i;
> +
> + /* Address Phrase */
> + val = imx8mq_phy_ctrl_reg_addr(imx_phy, offset);
> + if (val)
> + return val;
> +
> + /* Read Phrase */
> + writel(readl(cr_ctrl) | PHY_CRCTL_CR_READ, cr_ctrl);
> +
> + /* Wait CRSR[16] == 1 */
> + i = IMX8M_PHY_DEBUG_PORT_LOOP_TIMEOUT;
> + while (!(readl(cr_sr) & PHY_CRSR_CR_ACK) && i > 0)
> + i--;
> + if (i == 0)
> + goto cr_read_err;
> +
> + val = readl(cr_sr);
> + writel(val & ~PHY_CRCTL_CR_READ, cr_ctrl);
> +
> + /* Wait CRSR[16] == 0 */
> + i = IMX8M_PHY_DEBUG_PORT_LOOP_TIMEOUT;
> + while (!(readl(cr_sr) & PHY_CRSR_CR_ACK) && i > 0)
> + i--;
> + if (i == 0)
> + goto cr_read_err;
> +
> + return val;
> +
> +cr_read_err:
> + dev_err(dev, "Failed to read reg 0x%x.\n", offset);
> + return -EIO;
> +}
> +
> +static int imx8mq_phy_ctrl_reg_write(struct imx8mq_usb_phy *imx_phy,
> + u16 offset, u16 val)
> +{
> + void __iomem *cr_ctrl = imx_phy->base + PHY_CRCTL;
> + void __iomem *cr_sr = imx_phy->base + PHY_CRSR;
> + struct device *dev = &imx_phy->phy->dev;
> + int i, ret;
> +
> + /* Address Phrase */
> + ret = imx8mq_phy_ctrl_reg_addr(imx_phy, offset);
> + if (ret)
> + return ret;
> +
> + writel(val, cr_ctrl);
> +
> + /* Set cr_cap_data to be 1'b1 */
> + writel(readl(cr_ctrl) | PHY_CRCTL_CAP_DATA, cr_ctrl);
> + /* Wait CRSR[16] == 1 */
> + i = IMX8M_PHY_DEBUG_PORT_LOOP_TIMEOUT;
> + while (!(readl(cr_sr) & PHY_CRSR_CR_ACK) && i > 0)
> + i--;
> + if (i == 0)
> + goto cr_write_err;

seems like a repeated pattern, maybe move to a helper. (if driver used
regmap, it could have used helpers from regmap for this polling)

> +
> + /* Clear cr_cap_data to be 1'br0 */
> + writel(readl(cr_ctrl) & ~PHY_CRCTL_CAP_DATA, cr_ctrl);
> + /* Wait CRSR[16] == 0 */
> + i = IMX8M_PHY_DEBUG_PORT_LOOP_TIMEOUT;
> + while ((readl(cr_sr) & PHY_CRSR_CR_ACK) && i > 0)
> + i--;
> + if (i == 0)
> + goto cr_write_err;
> +
> + /* Set cr_write to be 1'b1 */
> + writel(readl(cr_ctrl) | PHY_CRCTL_CR_WRITE, cr_ctrl);
> + /* Wait CRSR[16] == 1 */
> + i = IMX8M_PHY_DEBUG_PORT_LOOP_TIMEOUT;
> + while (!(readl(cr_sr) & PHY_CRSR_CR_ACK) && i > 0)
> + i--;
> + if (i == 0)
> + goto cr_write_err;
> +
> + /* Clear cr_write to be 1'br0 */
> + writel(readl(cr_ctrl) & ~PHY_CRCTL_CR_WRITE, cr_ctrl);
> + /* Wait CRSR[16] == 0 */
> + i = IMX8M_PHY_DEBUG_PORT_LOOP_TIMEOUT;
> + while ((readl(cr_sr) & PHY_CRSR_CR_ACK) && i > 0)
> + i--;
> + if (i == 0)
> + goto cr_write_err;
> +
> + return 0;
> +
> +cr_write_err:
> + dev_err(dev, "Failed to write reg 0x%x.\n", offset);
> + return -EIO;
> +}
> +
> +static int ctrl_reg_value_show(struct seq_file *s, void *unused)
> +{
> + struct imx8mq_usb_phy *imx_phy = s->private;
> + u16 i, val, base = imx_phy->cr_access_base;
> +
> + for (i = 0; i < imx_phy->cr_read_count; i++) {
> + val = imx8mq_phy_ctrl_reg_read(imx_phy, base + i);
> + seq_printf(s, "Control Register 0x%x value is 0x%4x\n",
> + base + i, val);
> + }
> +
> + return 0;
> +}
> +
> +static int ctrl_reg_value_open(struct inode *inode, struct file *file)
> +{
> + return single_open(file, ctrl_reg_value_show, inode->i_private);
> +}
> +
> +static ssize_t ctrl_reg_value_write(struct file *file, const char __user *ubuf,
> + size_t count, loff_t *ppos)
> +{
> + struct seq_file *s = file->private_data;
> + struct imx8mq_usb_phy *imx_phy = s->private;
> + u16 cr_value;
> + int ret;
> +
> + ret = kstrtou16_from_user(ubuf, count, 16, &cr_value);
> + if (ret)
> + return ret;
> +
> + imx8mq_phy_ctrl_reg_write(imx_phy, imx_phy->cr_access_base, cr_value);
> +
> + return count;
> +}
> +
> +static const struct file_operations ctrl_reg_value_fops = {
> + .open = ctrl_reg_value_open,
> + .write = ctrl_reg_value_write,
> + .read = seq_read,
> + .llseek = seq_lseek,
> + .release = single_release,
> +};

please use DEFINE_DEBUGFS_ATTRIBUTE for this

> +
> +static void debug_create_files(struct imx8mq_usb_phy *imx_phy)
> +{
> + struct device *dev = &imx_phy->phy->dev;
> +
> + imx_phy->debugfs = debugfs_create_dir(dev_name(dev), imx_phy->phy->debugfs);
> +
> + debugfs_create_x16("ctrl_reg_base", 0600, imx_phy->debugfs,
> + &imx_phy->cr_access_base);
> + debugfs_create_x16("ctrl_reg_count", 0600, imx_phy->debugfs,
> + &imx_phy->cr_read_count);
> + debugfs_create_file("ctrl_reg_value", 0600, imx_phy->debugfs,
> + imx_phy, &ctrl_reg_value_fops);
> +
> + imx_phy->cr_access_base = 0;
> + imx_phy->cr_read_count = 1;
> +}
> +
> +static void debug_remove_files(struct imx8mq_usb_phy *imx_phy)
> +{
> + debugfs_remove_recursive(imx_phy->debugfs);
> }
>
> static void imx8m_get_phy_tuning_data(struct imx8mq_usb_phy *imx_phy)
> @@ -724,6 +941,7 @@ static int imx8mq_usb_phy_probe(struct platform_device *pdev)
> "failed to get tca\n");
>
> imx8m_get_phy_tuning_data(imx_phy);
> + debug_create_files(imx_phy);

please use phy->debugfs as root node

--
~Vinod