Re: [PATCH v2 4/4] phy: freescale: pcie: initialize the imx8 pcie standalone phy driver

[Lucas Stach <l.stach@pengutronix.de>]

Hi Richard,

Am Dienstag, dem 28.09.2021 um 07:09 +0000 schrieb Richard Zhu:
> > -----Original Message-----
> > From: Lucas Stach <l.stach@pengutronix.de>
> > Sent: Monday, September 27, 2021 4:43 PM
> > To: Richard Zhu <hongxing.zhu@nxp.com>; kishon@ti.com; vkoul@kernel.org;
> > robh@kernel.org; galak@kernel.crashing.org; shawnguo@kernel.org
> > Cc: linux-phy@lists.infradead.org; devicetree@vger.kernel.org;
> > linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org;
> > kernel@pengutronix.de; dl-linux-imx <linux-imx@nxp.com>
> > Subject: Re: [PATCH v2 4/4] phy: freescale: pcie: initialize the imx8 pcie
> > standalone phy driver
> > 
> > Am Sonntag, dem 26.09.2021 um 15:39 +0800 schrieb Richard Zhu:
> > > Add the standalone i.MX8 PCIe PHY driver.
> > > Some reset bits should be manipulated between PHY configurations and
> > > status check(internal PLL is locked or not).
> > > So, do the PHY configuration in the phy_calibrate().
> > > And check the PHY is ready or not in the phy_init().
> > 
> > I would really like to see the PCIe controller driver side of this also, as it's hard
> > to review standalone. For example I'm not sure if some of those reset bits
> > should also be driven from the PHY driver, even if they are currently hooked
> > up to the controller driver.
> > 
> > Also I think the IOMUX GPR register handling belongs in the PHY driver, as it's
> > configuring the reference clock routing.
> > 
> [Richard Zhu] Sorry to bring inconvenience to you. I would send out the v3
>  patch-set and the i.MX8MM PCIe controller driver patches after I'm back from the
>  national holiday tomorrow(about one week). 

No problem. :) I'm just pointing out that I probably won't be able to
invest more time reviewing this before I can get the full picture.

> Although most of the IOMUX GPR bits are related to PHY, but there are some bits are
>  defined only for controller. For example, the device_type of the controller, the clkreq#
>  signal control in L1SS, and so on. We can't encapsulate all the GPR bits setting into PHY driver.
> So, it's better to let controller driver to handle the general register bits manipulations.
> How do you think about that?

I still think we should split the drivers along the functional
boundaries. It's quite confusing and probably going to be a maintenance
issues when some of the PHY handling bits are still located in the
controller driver, while we have a separate PHY driver.

As the GPR region is handled by a regmap we should have no issues
accessing even the same register from different drivers. So my vote is
on moving the GPR bits related to PHY clocking to this driver.

> 
> > > 
> > > Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
> > > ---
> > >  drivers/phy/freescale/Kconfig             |   9 ++
> > >  drivers/phy/freescale/Makefile            |   1 +
> > >  drivers/phy/freescale/phy-fsl-imx8-pcie.c | 167
> > > ++++++++++++++++++++++
> > >  3 files changed, 177 insertions(+)
> > >  create mode 100644 drivers/phy/freescale/phy-fsl-imx8-pcie.c
> > 
> > From what I know, there are several quite different PCIe PHYs used in the
> > different i.MX8 variants. I'm not sure if we want to stuff them all into one file.
> > I guess we should be more specific here and call this imx8m-phy, or even
> > imx8mm-phy.
> [Richard Zhu] Good suggestions, I think imx8m-phy is better, since the i.MX8MQ/MM/MP
>  have the similar architecture of the PCIe PHY implementation.
> 
> > 
> > > 
> > > diff --git a/drivers/phy/freescale/Kconfig
> > > b/drivers/phy/freescale/Kconfig index 320630ffe3cd..da078a676fbc
> > > 100644
> > > --- a/drivers/phy/freescale/Kconfig
> > > +++ b/drivers/phy/freescale/Kconfig
> > > @@ -14,3 +14,12 @@ config PHY_MIXEL_MIPI_DPHY
> > >  	help
> > >  	  Enable this to add support for the Mixel DSI PHY as found
> > >  	  on NXP's i.MX8 family of SOCs.
> > > +
> > > +config PHY_FSL_IMX8_PCIE
> > > +	tristate "Freescale i.MX8 PCIE PHY"
> > > +	depends on OF && HAS_IOMEM
> > > +	select GENERIC_PHY
> > > +	default ARCH_MXC
> > > +	help
> > > +	  Enable this to add support for the PCIE PHY as found on i.MX8
> > > +	  family of SOCs.
> > > diff --git a/drivers/phy/freescale/Makefile
> > > b/drivers/phy/freescale/Makefile index 1d02e3869b45..9fd467b58621
> > > 100644
> > > --- a/drivers/phy/freescale/Makefile
> > > +++ b/drivers/phy/freescale/Makefile
> > > @@ -1,3 +1,4 @@
> > >  # SPDX-License-Identifier: GPL-2.0-only
> > >  obj-$(CONFIG_PHY_FSL_IMX8MQ_USB)	+= phy-fsl-imx8mq-usb.o
> > >  obj-$(CONFIG_PHY_MIXEL_MIPI_DPHY)	+= phy-fsl-imx8-mipi-dphy.o
> > > +obj-$(CONFIG_PHY_FSL_IMX8_PCIE)		+= phy-fsl-imx8-pcie.o
> > > diff --git a/drivers/phy/freescale/phy-fsl-imx8-pcie.c
> > > b/drivers/phy/freescale/phy-fsl-imx8-pcie.c
> > > new file mode 100644
> > > index 000000000000..ff47d6b83686
> > > --- /dev/null
> > > +++ b/drivers/phy/freescale/phy-fsl-imx8-pcie.c
> > > @@ -0,0 +1,167 @@
> > > +// SPDX-License-Identifier: GPL-2.0+
> > > +/*
> > > + * Copyright 2021 NXP
> > > + */
> > > +
> > > +#include <linux/clk.h>
> > > +#include <linux/io.h>
> > > +#include <linux/iopoll.h>
> > > +#include <linux/delay.h>
> > > +#include <linux/module.h>
> > > +#include <linux/phy/phy.h>
> > > +#include <linux/platform_device.h>
> > > +#include <dt-binding/phy/phy-fsl-imx8-pcie.h>
> > > +
> > > +#define IMX8MM_PCIE_PHY_CMN_REG061	0x184
> > > +#define  ANA_PLL_CLK_OUT_TO_EXT_IO_EN	BIT(0)
> > > +#define IMX8MM_PCIE_PHY_CMN_REG062	0x188
> > > +#define  ANA_PLL_CLK_OUT_TO_EXT_IO_SEL	BIT(3)
> > > +#define IMX8MM_PCIE_PHY_CMN_REG063	0x18C
> > > +#define  AUX_PLL_REFCLK_SEL_SYS_PLL	GENMASK(7, 6)
> > > +#define IMX8MM_PCIE_PHY_CMN_REG064	0x190
> > > +#define  ANA_AUX_RX_TX_SEL_TX		BIT(7)
> > > +#define  ANA_AUX_RX_TERM_GND_EN		BIT(3)
> > > +#define  ANA_AUX_TX_TERM		BIT(2)
> > > +#define IMX8MM_PCIE_PHY_CMN_REG065	0x194
> > > +#define  ANA_AUX_RX_TERM		(BIT(7) | BIT(4))
> > > +#define  ANA_AUX_TX_LVL			GENMASK(3, 0)
> > > +#define IMX8MM_PCIE_PHY_CMN_REG75	0x1D4
> > > +#define  PCIE_PHY_CMN_REG75_PLL_DONE	0x3
> > > +#define PCIE_PHY_TRSV_REG5		0x414
> > > +#define  PCIE_PHY_TRSV_REG5_GEN1_DEEMP	0x2D
> > > +#define PCIE_PHY_TRSV_REG6		0x418
> > > +#define  PCIE_PHY_TRSV_REG6_GEN2_DEEMP	0xF
> > > +
> > > +struct imx8_pcie_phy {
> > > +	u32		refclk_pad_mode;
> > > +	void __iomem	*base;
> > > +	struct clk	*clk;
> > > +	struct phy	*phy;
> > > +};
> > > +
> > > +static int imx8_pcie_phy_init(struct phy *phy) {
> > > +	int ret;
> > > +	u32 val;
> > > +	struct imx8_pcie_phy *imx8_phy = phy_get_drvdata(phy);
> > > +
> > > +	ret = readl_poll_timeout(imx8_phy->base +
> > IMX8MM_PCIE_PHY_CMN_REG75,
> > > +				 val, val == PCIE_PHY_CMN_REG75_PLL_DONE,
> > > +				 10, 20000);
> > > +	return ret;
> > > +}
> > > +
> > > +static int imx8_pcie_phy_cal(struct phy *phy) {
> > > +	u32 value, pad_mode;
> > > +	struct imx8_pcie_phy *imx8_phy = phy_get_drvdata(phy);
> > > +
> > > +	pad_mode = imx8_phy->refclk_pad_mode;
> > > +	if (pad_mode == IMX8_PCIE_REFCLK_PAD_INPUT) {
> > > +		/* Configure the pad as input */
> > > +		value = readl(imx8_phy->base +
> > IMX8MM_PCIE_PHY_CMN_REG061);
> > > +		writel(value & ~ANA_PLL_CLK_OUT_TO_EXT_IO_EN,
> > > +		       imx8_phy->base + IMX8MM_PCIE_PHY_CMN_REG061);
> > > +	} else if (pad_mode == IMX8_PCIE_REFCLK_PAD_OUTPUT) {
> > > +		/* Configure the PHY to output the refclock via pad */
> > > +		writel(ANA_PLL_CLK_OUT_TO_EXT_IO_EN,
> > > +		       imx8_phy->base + IMX8MM_PCIE_PHY_CMN_REG061);
> > > +		writel(ANA_PLL_CLK_OUT_TO_EXT_IO_SEL,
> > > +		       imx8_phy->base + IMX8MM_PCIE_PHY_CMN_REG062);
> > > +		writel(AUX_PLL_REFCLK_SEL_SYS_PLL,
> > > +		       imx8_phy->base + IMX8MM_PCIE_PHY_CMN_REG063);
> > > +		value = ANA_AUX_RX_TX_SEL_TX | ANA_AUX_TX_TERM;
> > > +		writel(value | ANA_AUX_RX_TERM_GND_EN,
> > > +		       imx8_phy->base + IMX8MM_PCIE_PHY_CMN_REG064);
> > > +		writel(ANA_AUX_RX_TERM | ANA_AUX_TX_LVL,
> > > +		       imx8_phy->base + IMX8MM_PCIE_PHY_CMN_REG065);
> > > +	}
> > > +
> > > +	/* Tune PHY de-emphasis setting to pass PCIe compliance. */
> > > +	writel(PCIE_PHY_TRSV_REG5_GEN1_DEEMP,
> > > +	       imx8_phy->base + PCIE_PHY_TRSV_REG5);
> > > +	writel(PCIE_PHY_TRSV_REG6_GEN2_DEEMP,
> > > +	       imx8_phy->base + PCIE_PHY_TRSV_REG6);
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static int imx8_pcie_phy_power_on(struct phy *phy) {
> > > +	struct imx8_pcie_phy *imx8_phy = phy_get_drvdata(phy);
> > > +
> > > +	return clk_prepare_enable(imx8_phy->clk);
> > 
> > Do we need to enable this clock when the refclock is supplied externally via
> > the pad?
> > 
> [Richard Zhu] Good question. I think this clock is not needed anymore if the refclock is sourced from external OSC.
> I just enable the PLL2_100Mhz here, since when internal PLL is used as refclock, the pll2_100Mhz should be turned on.
> Shall I remove the setting and just keep the callback for further extend usage(internal PLL used as refclk)?
> 
Yes, we should avoid turning on clocks that aren't needed. So the clock
enable here should be dependent on the pad-mode. When the clock is
supplied externally we don't want to enable the internal clock.

Regards,
Lucas

> > > +}
> > > +
> > > +static int imx8_pcie_phy_power_off(struct phy *phy) {
> > > +	struct imx8_pcie_phy *imx8_phy = phy_get_drvdata(phy);
> > > +
> > > +	clk_disable_unprepare(imx8_phy->clk);
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static const struct phy_ops imx8_pcie_phy_ops = {
> > > +	.init		= imx8_pcie_phy_init,
> > > +	.calibrate	= imx8_pcie_phy_cal,
> > > +	.power_on	= imx8_pcie_phy_power_on,
> > > +	.power_off	= imx8_pcie_phy_power_off,
> > > +	.owner		= THIS_MODULE,
> > > +};
> > > +
> > > +static int imx8_pcie_phy_probe(struct platform_device *pdev) {
> > > +	struct phy_provider *phy_provider;
> > > +	struct device *dev = &pdev->dev;
> > > +	struct device_node *np = dev->of_node;
> > > +	struct imx8_pcie_phy *imx8_phy;
> > > +	struct resource *res;
> > > +
> > > +	imx8_phy = devm_kzalloc(dev, sizeof(*imx8_phy), GFP_KERNEL);
> > > +	if (!imx8_phy)
> > > +		return -ENOMEM;
> > > +
> > > +	/* get PHY refclk pad mode */
> > > +	of_property_read_u32(np, "fsl,refclk-pad-mode",
> > > +			     &imx8_phy->refclk_pad_mode);
> > > +
> > > +	imx8_phy->clk = devm_clk_get(dev, "phy");
> > > +	if (IS_ERR(imx8_phy->clk)) {
> > > +		dev_err(dev, "failed to get imx pcie phy clock\n");
> > > +		return PTR_ERR(imx8_phy->clk);
> > > +	}
> > > +
> > > +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > > +	imx8_phy->base = devm_ioremap_resource(dev, res);
> > > +	if (IS_ERR(imx8_phy->base))
> > > +		return PTR_ERR(imx8_phy->base);
> > > +
> > > +	imx8_phy->phy = devm_phy_create(dev, NULL, &imx8_pcie_phy_ops);
> > > +	if (IS_ERR(imx8_phy->phy))
> > > +		return PTR_ERR(imx8_phy->phy);
> > > +
> > > +	phy_set_drvdata(imx8_phy->phy, imx8_phy);
> > > +
> > > +	phy_provider = devm_of_phy_provider_register(dev,
> > > +of_phy_simple_xlate);
> > > +
> > > +	return PTR_ERR_OR_ZERO(phy_provider); }
> > > +
> > > +static const struct of_device_id imx8_pcie_phy_of_match[] = {
> > > +	{.compatible = "fsl,imx8mm-pcie-phy",},
> > > +	{ },
> > > +};
> > > +MODULE_DEVICE_TABLE(of, imx8_pcie_phy_of_match);
> > > +
> > > +static struct platform_driver imx8_pcie_phy_driver = {
> > > +	.probe	= imx8_pcie_phy_probe,
> > > +	.driver = {
> > > +		.name	= "imx8-pcie-phy",
> > > +		.of_match_table	= imx8_pcie_phy_of_match,
> > > +	}
> > > +};
> > > +module_platform_driver(imx8_pcie_phy_driver);
> > > +
> > > +MODULE_DESCRIPTION("FSL IMX8 PCIE PHY driver");
> > > +MODULE_LICENSE("GPL");
> > 
>