Subject: Re: [PATCH V5 14/16] phy: tegra: Add PCIe PIPE2UPHY support

From: Thierry Reding <[email-masked]>
Date: Fri, 3 May 2019 13:35:58 +0200

On Wed, Apr 24, 2019 at 10:50:02AM +0530, Vidya Sagar wrote:
> Synopsys DesignWare core based PCIe controllers in Tegra 194 SoC interface
> with Universal PHY (UPHY) module through a PIPE2UPHY (P2U) module.
> For each PCIe lane of a controller, there is a P2U unit instantiated at
> hardware level. This driver provides support for the programming required
> for each P2U that is going to be used for a PCIe controller.
> 
> Signed-off-by: Vidya Sagar <[email-masked]>
> ---
> Changes since [v4]:
> * None
> 
> Changes since [v3]:
> * Rebased on top of linux-next top of the tree
> 
> Changes since [v2]:
> * Replaced spaces with tabs in Kconfig file
> * Sorted header file inclusion alphabetically
> 
> Changes since [v1]:
> * Added COMPILE_TEST in Kconfig
> * Removed empty phy_ops implementations
> * Modified code according to DT documentation file modifications
> 
>  drivers/phy/tegra/Kconfig             |   7 ++
>  drivers/phy/tegra/Makefile            |   1 +
>  drivers/phy/tegra/pcie-p2u-tegra194.c | 120 ++++++++++++++++++++++++++
>  3 files changed, 128 insertions(+)
>  create mode 100644 drivers/phy/tegra/pcie-p2u-tegra194.c
> 
> diff --git a/drivers/phy/tegra/Kconfig b/drivers/phy/tegra/Kconfig
> index a3b1de953fb7..06d423fa85b4 100644
> --- a/drivers/phy/tegra/Kconfig
> +++ b/drivers/phy/tegra/Kconfig
> @@ -6,3 +6,10 @@ config PHY_TEGRA_XUSB
>  
>  	  To compile this driver as a module, choose M here: the module will
>  	  be called phy-tegra-xusb.
> +
> +config PHY_TEGRA194_PCIE_P2U
> +	tristate "NVIDIA Tegra P2U PHY Driver"
> +	depends on ARCH_TEGRA || COMPILE_TEST
> +	select GENERIC_PHY
> +	help
> +	  Enable this to support the P2U (PIPE to UPHY) that is part of Tegra 19x SOCs.
> diff --git a/drivers/phy/tegra/Makefile b/drivers/phy/tegra/Makefile
> index a93cd9a499b2..1aaca794f40c 100644
> --- a/drivers/phy/tegra/Makefile
> +++ b/drivers/phy/tegra/Makefile
> @@ -5,3 +5,4 @@ phy-tegra-xusb-$(CONFIG_ARCH_TEGRA_124_SOC) += xusb-tegra124.o
>  phy-tegra-xusb-$(CONFIG_ARCH_TEGRA_132_SOC) += xusb-tegra124.o
>  phy-tegra-xusb-$(CONFIG_ARCH_TEGRA_210_SOC) += xusb-tegra210.o
>  phy-tegra-xusb-$(CONFIG_ARCH_TEGRA_186_SOC) += xusb-tegra186.o
> +obj-$(CONFIG_PHY_TEGRA194_PCIE_P2U) += pcie-p2u-tegra194.o
> diff --git a/drivers/phy/tegra/pcie-p2u-tegra194.c b/drivers/phy/tegra/pcie-p2u-tegra194.c
> new file mode 100644
> index 000000000000..a5d85e411088
> --- /dev/null
> +++ b/drivers/phy/tegra/pcie-p2u-tegra194.c
> @@ -0,0 +1,120 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * P2U (PIPE to UPHY) driver for Tegra T194 SoC
> + *
> + * Copyright (C) 2019 NVIDIA Corporation.
> + *
> + * Author: Vidya Sagar <[email-masked]>
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_platform.h>
> +#include <linux/phy/phy.h>
> +#include <linux/platform_device.h>
> +#include <soc/tegra/bpmp-abi.h>

Looks to me like not all of the above are actually needed. I don't see
anything from delay.h used, and you certainly aren't using anything from
soc/tegra/bpmp-abi.h either.

> +
> +#define P2U_PERIODIC_EQ_CTRL_GEN3	0xc0
> +#define P2U_PERIODIC_EQ_CTRL_GEN3_PERIODIC_EQ_EN		BIT(0)
> +#define P2U_PERIODIC_EQ_CTRL_GEN3_INIT_PRESET_EQ_TRAIN_EN	BIT(1)
> +#define P2U_PERIODIC_EQ_CTRL_GEN4	0xc4
> +#define P2U_PERIODIC_EQ_CTRL_GEN4_INIT_PRESET_EQ_TRAIN_EN	BIT(1)
> +
> +#define P2U_RX_DEBOUNCE_TIME				0xa4
> +#define P2U_RX_DEBOUNCE_TIME_DEBOUNCE_TIMER_MASK	0xffff
> +#define P2U_RX_DEBOUNCE_TIME_DEBOUNCE_TIMER_VAL		160
> +
> +struct tegra_p2u {
> +	void __iomem *base;
> +};
> +
> +static int tegra_p2u_power_on(struct phy *x)
> +{
> +	struct tegra_p2u *phy = phy_get_drvdata(x);
> +	u32 val;
> +
> +	val = readl(phy->base + P2U_PERIODIC_EQ_CTRL_GEN3);
> +	val &= ~P2U_PERIODIC_EQ_CTRL_GEN3_PERIODIC_EQ_EN;
> +	val |= P2U_PERIODIC_EQ_CTRL_GEN3_INIT_PRESET_EQ_TRAIN_EN;
> +	writel(val, phy->base + P2U_PERIODIC_EQ_CTRL_GEN3);
> +
> +	val = readl(phy->base + P2U_PERIODIC_EQ_CTRL_GEN4);
> +	val |= P2U_PERIODIC_EQ_CTRL_GEN4_INIT_PRESET_EQ_TRAIN_EN;
> +	writel(val, phy->base + P2U_PERIODIC_EQ_CTRL_GEN4);
> +
> +	val = readl(phy->base + P2U_RX_DEBOUNCE_TIME);
> +	val &= ~P2U_RX_DEBOUNCE_TIME_DEBOUNCE_TIMER_MASK;
> +	val |= P2U_RX_DEBOUNCE_TIME_DEBOUNCE_TIMER_VAL;
> +	writel(val, phy->base + P2U_RX_DEBOUNCE_TIME);
> +
> +	return 0;
> +}
> +
> +static const struct phy_ops ops = {
> +	.power_on	= tegra_p2u_power_on,
> +	.owner		= THIS_MODULE,

I think it's perhaps best to just stick with single spaces around the =
instead of trying to arbitrarily align these. See below for why I think
so.

> +};
> +
> +static int tegra_p2u_probe(struct platform_device *pdev)
> +{
> +	struct phy_provider *phy_provider;
> +	struct device *dev = &pdev->dev;
> +	struct phy *generic_phy;
> +	struct tegra_p2u *phy;
> +	struct resource *res;
> +
> +	phy = devm_kzalloc(dev, sizeof(*phy), GFP_KERNEL);
> +	if (!phy)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "ctl");
> +	phy->base = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(phy->base))
> +		return PTR_ERR_OR_ZERO(phy->base);
> +
> +	platform_set_drvdata(pdev, phy);

You could use dev_set_drvdata() here since you already use dev (instead
of pdev) everywhere else.

> +
> +	generic_phy = devm_phy_create(dev, NULL, &ops);
> +	if (IS_ERR(generic_phy))
> +		return PTR_ERR_OR_ZERO(generic_phy);
> +
> +	phy_set_drvdata(generic_phy, phy);
> +
> +	phy_provider = devm_of_phy_provider_register(dev, of_phy_simple_xlate);
> +	if (IS_ERR(phy_provider))
> +		return PTR_ERR_OR_ZERO(phy_provider);
> +
> +	return 0;
> +}
> +
> +static int tegra_p2u_remove(struct platform_device *pdev)
> +{
> +	return 0;
> +}

I thought it had already been mentioned that you don't need to implement
this if it's empty?

> +
> +static const struct of_device_id tegra_p2u_id_table[] = {
> +	{
> +		.compatible = "nvidia,tegra194-p2u",
> +	},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, tegra_p2u_id_table);
> +
> +static struct platform_driver tegra_p2u_driver = {
> +	.probe		= tegra_p2u_probe,
> +	.remove		= tegra_p2u_remove,
> +	.driver		= {
> +		.name	= "tegra194-p2u",
> +		.of_match_table = tegra_p2u_id_table,

Again, I don't think the artificial padding does this any good. For
example, the .driver.name's assignment operator is padded to the same
column as members of the parent structure, so that's confusing to read.
Also, .of_match_table is not padded at all, so it's inconsistent. Just
use single spaces around =. That's easy to keep consistent and really
doesn't read that bad.

> +	},
> +};
> +
> +module_platform_driver(tegra_p2u_driver);

It's customary to have no blank line between the closing "};" and the
module_platform_driver() macro.

Thierry

> +
> +MODULE_AUTHOR("Vidya Sagar <[email-masked]>");
> +MODULE_DESCRIPTION("NVIDIA Tegra PIPE2UPHY PHY driver");
> +MODULE_LICENSE("GPL v2");
> -- 
> 2.17.1
> 
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