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Subject: Re: [PATCH V10 13/15] phy: tegra: Add PCIe PIPE2UPHY support
To:     Kishon Vijay Abraham I <kishon@ti.com>,
        Vidya Sagar <vidyas@nvidia.com>, lorenzo.pieralisi@arm.com,
        bhelgaas@google.com, robh+dt@kernel.org, mark.rutland@arm.com,
        thierry.reding@gmail.com, jonathanh@nvidia.com,
        catalin.marinas@arm.com, will.deacon@arm.com, jingoohan1@gmail.com,
        gustavo.pimentel@synopsys.com
Cc:     mperttunen@nvidia.com, linux-pci@vger.kernel.org,
        devicetree@vger.kernel.org, linux-tegra@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        kthota@nvidia.com, mmaddireddy@nvidia.com, sagar.tv@gmail.com
References: <20190612095339.20118-1-vidyas@nvidia.com>
 <20190612095339.20118-14-vidyas@nvidia.com>
 <9e699085-ef5e-f7be-e27c-23907ba92c82@ti.com>
From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <68a6579b-af28-ed7e-35f8-d857638368ba@gmail.com>
Date:   Fri, 21 Jun 2019 02:23:50 +0300
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20.06.2019 10:24, Kishon Vijay Abraham I пишет:
> 
> 
> On 12/06/19 3:23 PM, 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.
> 
> One minor comment below. With that fixed
> 
> Acked-by: Kishon Vijay Abraham I <kishon@ti.com>
>>
>> Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
>> ---
>> Changes since [v9]:
>> * Used _relaxed() versions of readl() & writel()
>>
>> 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 | 120 +++++++++++++++++++++++++++
>>  3 files changed, 128 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..df009abd2482
>> --- /dev/null
>> +++ b/drivers/phy/tegra/phy-tegra194-p2u.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 <vidyas@nvidia.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 inline void p2u_writel(struct tegra_p2u *phy, const u32 value,
>> +			      const u32 reg)
>> +{
>> +	writel_relaxed(value, phy->base + reg);
>> +}
>> +
>> +static inline u32 p2u_readl(struct tegra_p2u *phy, const u32 reg)
>> +{
>> +	return readl_relaxed(phy->base + reg);
>> +}
>> +
>> +static int tegra_p2u_power_on(struct phy *x)
>> +{
>> +	struct tegra_p2u *phy = phy_get_drvdata(x);
>> +	u32 val;
>> +
>> +	val = p2u_readl(phy, 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;
>> +	p2u_writel(phy, val, P2U_PERIODIC_EQ_CTRL_GEN3);
>> +
>> +	val = p2u_readl(phy, P2U_PERIODIC_EQ_CTRL_GEN4);
>> +	val |= P2U_PERIODIC_EQ_CTRL_GEN4_INIT_PRESET_EQ_TRAIN_EN;
>> +	p2u_writel(phy, val, P2U_PERIODIC_EQ_CTRL_GEN4);
>> +
>> +	val = p2u_readl(phy, P2U_RX_DEBOUNCE_TIME);
>> +	val &= ~P2U_RX_DEBOUNCE_TIME_DEBOUNCE_TIMER_MASK;
>> +	val |= P2U_RX_DEBOUNCE_TIME_DEBOUNCE_TIMER_VAL;
>> +	p2u_writel(phy, val, P2U_RX_DEBOUNCE_TIME);
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct phy_ops ops = {
>> +	.power_on = tegra_p2u_power_on,
>> +	.owner = THIS_MODULE,
>> +};
>> +
>> +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);
>> +
>> +	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;
> 
> Just make this..
> phy_provider = devm_of_phy_provider_register(dev, of_phy_simple_xlate);
> return PTR_ERR_OR_ZERO(phy_provider);

There is a need to s/PTR_ERR_OR_ZERO/PTR_ERR/ for all of the occurrences
in this patch because it is impossible to get ZERO if we already know
that pointer is a error.

Secondly, it is always cleaner to return 0 explicitly on success and
PTR_ERR_OR_ZERO(phy_provider) is a much less readable form than a simple
return 0. So I'm suggesting to keep that part as-is.