Re: [PATCH 2/2] phy: Add driver for mixel dphy

Hi Guido.

Patch looks good but a few comments below.

Sam

On Fri, Jan 25, 2019 at 11:14:46AM +0100, Guido Günther wrote:

This adds support for the Mixel DPHY as found on i.MX8 CPUs but since this is an IP core it will likely be found on others in the future. So instead of adding this to the nwl host driver make it a generic PHY driver.

The driver supports the i.MX8MQ. Support for i.MX8QM and i.MX8QXP can be added once the necessary system controller bits are in via mixel_dpy_ops.

Signed-off-by: Guido Günther agx@sigxcpu.org

drivers/phy/Kconfig | 7 + drivers/phy/Makefile | 1 + drivers/phy/phy-mixel-mipi-dphy.c | 449 ++++++++++++++++++++++++++++++ 3 files changed, 457 insertions(+) create mode 100644 drivers/phy/phy-mixel-mipi-dphy.c

diff --git a/drivers/phy/Kconfig b/drivers/phy/Kconfig index 250abe290ca1..9195b5876bcc 100644 --- a/drivers/phy/Kconfig +++ b/drivers/phy/Kconfig @@ -48,6 +48,13 @@ config PHY_XGENE help This option enables support for APM X-Gene SoC multi-purpose PHY.

+config PHY_MIXEL_MIPI_DPHY

• bool
• depends on OF
• select GENERIC_PHY
• select GENERIC_PHY_MIPI_DPHY
• default ARCH_MXC && ARM64

Is it correct that driver is mandatory if ARCH_MXC is y? There is no prompt to allow the user to select it. Or in other words - will all i.MX8 user need it?

source "drivers/phy/allwinner/Kconfig" source "drivers/phy/amlogic/Kconfig" source "drivers/phy/broadcom/Kconfig" diff --git a/drivers/phy/Makefile b/drivers/phy/Makefile index 0d9fddc498a6..264f570b67bf 100644 --- a/drivers/phy/Makefile +++ b/drivers/phy/Makefile @@ -15,6 +15,7 @@ obj-$(CONFIG_ARCH_MEDIATEK) += mediatek/ obj-$(CONFIG_ARCH_RENESAS) += renesas/ obj-$(CONFIG_ARCH_ROCKCHIP) += rockchip/ obj-$(CONFIG_ARCH_TEGRA) += tegra/ +obj-$(CONFIG_PHY_MIXEL_MIPI_DPHY) += phy-mixel-mipi-dphy.o obj-y += broadcom/ \ cadence/ \ freescale/ \ diff --git a/drivers/phy/phy-mixel-mipi-dphy.c b/drivers/phy/phy-mixel-mipi-dphy.c new file mode 100644 index 000000000000..8a43dab79cee --- /dev/null +++ b/drivers/phy/phy-mixel-mipi-dphy.c

There is already a PHY named phy-fsl-imx8mq-usb, located in the freescale subdirectory. Why locate another imx8 PHY in the top level directory with another naming convention?

@@ -0,0 +1,449 @@ +/*

• • Copyright 2017 NXP
• • Copyright 2019 Purism SPC
• • SPDX-License-Identifier: GPL-2.0
• */

SPDX-License-Identifier goes in at first line with //. It is documented somewhere. Also, did you double check that GPL 2.0 is correct?

+/* #define DEBUG 1 */

There is no reference to DEBUG in this file - delete?

+#include <linux/clk.h> +#include <linux/clk-provider.h> +#include <linux/delay.h> +#include <linux/io.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/of.h> +#include <linux/of_platform.h> +#include <linux/phy/phy.h> +#include <linux/platform_device.h>

+/* DPHY registers */ +#define DPHY_PD_DPHY 0x00 +#define DPHY_M_PRG_HS_PREPARE 0x04 +#define DPHY_MC_PRG_HS_PREPARE 0x08 +#define DPHY_M_PRG_HS_ZERO 0x0c +#define DPHY_MC_PRG_HS_ZERO 0x10 +#define DPHY_M_PRG_HS_TRAIL 0x14 +#define DPHY_MC_PRG_HS_TRAIL 0x18 +#define DPHY_PD_PLL 0x1c +#define DPHY_TST 0x20 +#define DPHY_CN 0x24 +#define DPHY_CM 0x28 +#define DPHY_CO 0x2c +#define DPHY_LOCK 0x30 +#define DPHY_LOCK_BYP 0x34 +#define DPHY_TX_RCAL 0x38 +#define DPHY_AUTO_PD_EN 0x3c +#define DPHY_RXLPRP 0x40 +#define DPHY_RXCDRP 0x44

+#define MBPS(x) ((x) * 1000000)

+#define DATA_RATE_MAX_SPEED MBPS(1500) +#define DATA_RATE_MIN_SPEED MBPS(80)

+#define CN_BUF 0xcb7a89c0 +#define CO_BUF 0x63 +#define CM(x) ( \

• ((x) <  32)?0xe0|((x)-16) :	\
  

• ((x) <  64)?0xc0|((x)-32) :	\
  

• ((x) < 128)?0x80|((x)-64) :	\
  

• ((x) - 128))
  

+#define CN(x) (((x) == 1)?0x1f : (((CN_BUF)>>((x)-1))&0x1f)) +#define CO(x) ((CO_BUF)>>(8-(x))&0x3)

+/* PHY power on is LOW_ENABLE */ +#define PWR_ON 0 +#define PWR_OFF 1

+struct mixel_dphy_cfg {

• u32 cm;
• u32 cn;
• u32 co;
• unsigned long hs_clk_rate;
• u8 mc_prg_hs_prepare;
• u8 m_prg_hs_prepare;
• u8 mc_prg_hs_zero;
• u8 m_prg_hs_zero;
• u8 mc_prg_hs_trail;
• u8 m_prg_hs_trail;

+};

For the naive reader it would be helpful to spell out the names in a comment. As I assume the names comes from the data sheet the short names are OK - but let others know the purpose.

+struct mixel_dphy_priv; +struct mixel_dphy_ops {

• int (*probe)(struct mixel_dphy_priv *priv);
• int (*power_on)(struct phy *phy);
• int (*power_off)(struct phy *phy);

+};

Consider same argument for all three ops, less suprises. But then probe() is called before we have a phy, so this may be the best option.

+struct mixel_dphy_priv {

• struct mixel_dphy_cfg cfg;
• void __iomem *regs;
• struct clk *phy_ref_clk;
• struct mutex lock;
• const struct mixel_dphy_ops *ops;

+};

Document what the lock protects, or find a better name for the lock to document it

+/* Find a ratio close to the desired one using continued fraction

• approximation ending either at exact match or maximum allowed
• nominator, denominator. */

Use kernel style comments /* * Bla bla * more bla */

+static void get_best_ratio(unsigned long *pnum, unsigned long *pdenom, unsigned max_n, unsigned max_d)

Wrap line to stay below 80 chars. Use checkpatch to help you sport things like this.

+{

• unsigned long a = *pnum;
• unsigned long b = *pdenom;
• unsigned long c;
• unsigned n[] = {0, 1};
• unsigned d[] = {1, 0};
• unsigned whole;
• unsigned i = 1;
• while (b) {

Add empty line after last local variable.

• i ^= 1;
  

• whole = a / b;
  

• n[i] += (n[i ^ 1] * whole);
  

• d[i] += (d[i ^ 1] * whole);
  

• if ((n[i] > max_n) || (d[i] > max_d)) {
  

• 	i ^= 1;
  

• 	break;
  

• }
  

• c = a - (b * whole);
  

• a = b;
  

• b = c;
  

• }
• *pnum = n[i];
• *pdenom = d[i];

+}

+static int mixel_dphy_config_from_opts(struct phy *phy,

•       struct phy_configure_opts_mipi_dphy *dphy_opts,
  

•       struct mixel_dphy_cfg *cfg)
  

+{

Align extra paratmers below the first parameter using tabs and add necessary spaces.

• struct mixel_dphy_priv *priv = dev_get_drvdata(phy->dev.parent);
• unsigned long ref_clk = clk_get_rate(priv->phy_ref_clk);
• int i;
• unsigned long numerator, denominator, frequency;
• unsigned step;

+static int mixel_dphy_ref_power_on(struct phy *phy) +{

• struct mixel_dphy_priv *priv = phy_get_drvdata(phy);
• u32 lock, timeout;
• int ret = 0;
• mutex_lock(&priv->lock);
• clk_prepare_enable(priv->phy_ref_clk);
• phy_write(phy, PWR_ON, DPHY_PD_DPHY);
• phy_write(phy, PWR_ON, DPHY_PD_PLL);
• timeout = 100;
• while (!(lock = phy_read(phy, DPHY_LOCK))) {

• udelay(10);
  

• if (--timeout == 0) {
  

• 	dev_err(&phy->dev, "Could not get DPHY lock!\n");
  

• 	mutex_unlock(&priv->lock);
  

• 	return -EINVAL;
  

• }
  

USe goto to have a single exit path where you do mutex_unlock()

• }
• mutex_unlock(&priv->lock);
• return ret;

+}

• mutex_lock(&priv->lock);
• phy_write(phy, 0x00, DPHY_LOCK_BYP);
• phy_write(phy, 0x01, DPHY_TX_RCAL);
• phy_write(phy, 0x00, DPHY_AUTO_PD_EN);
• phy_write(phy, 0x01, DPHY_RXLPRP);
• phy_write(phy, 0x01, DPHY_RXCDRP);
• phy_write(phy, 0x25, DPHY_TST);
• mixel_phy_set_hs_timings(phy);
• ret = mixel_dphy_set_pll_params(phy);
• if (ret < 0) {

• mutex_unlock(&priv->lock);
  

• return ret;
  

• }

USe goto to have a single exit path where you do mutex_unlock()

• mutex_unlock(&priv->lock);
• return 0;

+}

+/*

• • This is the reference implementation of DPHY hooks. Specific integration of
• • this IP may have to re-implement some of them depending on how they decided
• • to wire things in the SoC.
• */

+static const struct mixel_dphy_ops mixel_dphy_ref_ops = {

• .power_on = mixel_dphy_ref_power_on,
• .power_off = mixel_dphy_ref_power_off,

+};

+static const struct phy_ops mixel_dphy_ops = {

• .power_on = mixel_dphy_power_on,
• .power_off = mixel_dphy_power_off,
• .configure = mixel_dphy_configure,
• .validate = mixel_dphy_validate,
• .owner = THIS_MODULE,

+};

This is confusing. We have struct mixel_dphy_ops => mixel_dphy_ref_ops And then struct phy_ops => mixel_dphy_ops

So reading this there are to uses of mixel_dphy_ops, one is a struct, and another is an instance of another type. Try to find a niming scheme that is less confusing.

+static const struct of_device_id mixel_dphy_of_match[] = {

• { .compatible = "mixel,imx8mq-mipi-dphy", .data = &mixel_dphy_ref_ops },
• { /* sentinel */ },

+};

Multi-line to keep line shorter?

+MODULE_DEVICE_TABLE(of, mixel_dphy_of_match);

+static int mixel_dphy_probe(struct platform_device *pdev) +{

• struct device *dev = &pdev->dev;
• struct device_node *np = dev->of_node;
• struct phy_provider *phy_provider;
• struct mixel_dphy_priv *priv;
• struct resource *res;
• struct phy *phy;
• int ret;
• if (!np)

• return -ENODEV;
  

• priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
• if (!priv)

• return -ENOMEM;
  

• priv->ops = of_device_get_match_data(&pdev->dev);
• if (!priv->ops)

• return -EINVAL;
  

• res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
• if (!res)

• return -ENODEV;
  

• priv->regs = devm_ioremap(dev, res->start, SZ_256);
• if (IS_ERR(priv->regs))

• return PTR_ERR(priv->regs);
  

• priv->phy_ref_clk = devm_clk_get(&pdev->dev, "phy_ref");
• if (IS_ERR(priv->phy_ref_clk)) {

• dev_err(dev, "No phy_ref clock found");
  

• return PTR_ERR(priv->phy_ref_clk);
  

• }
• dev_dbg(dev, "phy_ref clock rate: %lu", clk_get_rate(priv->phy_ref_clk));
• mutex_init(&priv->lock);
• dev_set_drvdata(dev, priv);
• if (priv->ops->probe) {

• ret = priv->ops->probe(priv);
  

• if (ret)
  

• 	return ret;
  

• }
• phy = devm_phy_create(dev, np, &mixel_dphy_ops);
• if (IS_ERR(phy)) {

• dev_err(dev, "Failed to create phy %ld\n", PTR_ERR(phy));
  

• return PTR_ERR(phy);
  

• }
• phy_set_drvdata(phy, priv);
• phy_provider = devm_of_phy_provider_register(dev, of_phy_simple_xlate);
• return PTR_ERR_OR_ZERO(phy_provider);

+}

+static struct platform_driver mixel_dphy_driver = {

• .probe = mixel_dphy_probe,
• .driver = {

• .name = "mixel-mipi-dphy",
  

• .of_match_table	= mixel_dphy_of_match,
  

• }

+}; +module_platform_driver(mixel_dphy_driver);

+MODULE_AUTHOR("NXP Semiconductor"); +MODULE_DESCRIPTION("Mixel MIPI-DSI PHY driver");

+MODULE_LICENSE("GPL v2");

2.20.1

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