linux-kernel - Re: [PATCH V9 13/15] phy: tegra: Add PCIe PIPE2UPHY support

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Message-ID: <58349f3f-b9c2-2653-3a69-3bb5e836a9ef@gmail.com>
Date:   Mon, 10 Jun 2019 14:54:36 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Vidya Sagar <vidyas@...dia.com>, lorenzo.pieralisi@....com,
        bhelgaas@...gle.com, robh+dt@...nel.org, mark.rutland@....com,
        thierry.reding@...il.com, jonathanh@...dia.com, kishon@...com,
        catalin.marinas@....com, will.deacon@....com, jingoohan1@...il.com,
        gustavo.pimentel@...opsys.com
Cc:     mperttunen@...dia.com, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kthota@...dia.com, mmaddireddy@...dia.com, sagar.tv@...il.com
Subject: Re: [PATCH V9 13/15] phy: tegra: Add PCIe PIPE2UPHY support

07.06.2019 17:46, Vidya Sagar пишет:
> 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 <vidyas@...dia.com>
> ---
> Changes since [v8]:
> * Made it dependent on ARCH_TEGRA_194_SOC directly instead of ARCH_TEGRA
> 
> Changes since [v7]:
> * Changed P2U driver file name from pcie-p2u-tegra194.c to phy-tegra194-p2u.c
> 
> Changes since [v6]:
> * None
> 
> Changes since [v5]:
> * Addressed review comments from Thierry
> 
> 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/phy-tegra194-p2u.c | 109 +++++++++++++++++++++++++++
>  3 files changed, 117 insertions(+)
>  create mode 100644 drivers/phy/tegra/phy-tegra194-p2u.c
> 
> diff --git a/drivers/phy/tegra/Kconfig b/drivers/phy/tegra/Kconfig
> index e516967d695b..f9817c3ae85f 100644
> --- a/drivers/phy/tegra/Kconfig
> +++ b/drivers/phy/tegra/Kconfig
> @@ -7,3 +7,10 @@ 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_P2U
> +	tristate "NVIDIA Tegra194 PIPE2UPHY PHY driver"
> +	depends on ARCH_TEGRA_194_SOC || 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 64ccaeacb631..320dd389f34d 100644
> --- a/drivers/phy/tegra/Makefile
> +++ b/drivers/phy/tegra/Makefile
> @@ -6,3 +6,4 @@ 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_P2U) += phy-tegra194-p2u.o
> diff --git a/drivers/phy/tegra/phy-tegra194-p2u.c b/drivers/phy/tegra/phy-tegra194-p2u.c
> new file mode 100644
> index 000000000000..7b84b4c55e43
> --- /dev/null
> +++ b/drivers/phy/tegra/phy-tegra194-p2u.c
> @@ -0,0 +1,109 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * P2U (PIPE to UPHY) driver for Tegra T194 SoC
> + *
> + * Copyright (C) 2019 NVIDIA Corporation.
> + *
> + * Author: Vidya Sagar <vidyas@...dia.com>
> + */
> +
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_platform.h>
> +#include <linux/phy/phy.h>
> +
> +#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);

I'm wondering whether you're really need to insert memory barriers for
each readl/writel, can't the relaxed versions be used instead?

The same applies to other patches as well.