linux-kernel - Re: [PATCH 2/4] phy: socionext: add USB3 PHY driver for UniPhier SoC

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Message-ID: <52b96200-2234-9017-a317-f929eac9b266@ti.com>
Date:   Fri, 13 Jul 2018 12:45:06 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
CC:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        Masami Hiramatsu <masami.hiramatsu@...aro.org>,
        Jassi Brar <jaswinder.singh@...aro.org>
Subject: Re: [PATCH 2/4] phy: socionext: add USB3 PHY driver for UniPhier SoC

Hi,

On Wednesday 11 July 2018 05:35 PM, Kunihiko Hayashi wrote:
> On Mon, 9 Jul 2018 20:23:19 +0900 <hayashi.kunihiko@...ionext.com> wrote:
> 
>> Hi Kishon,
>> Thank you for your comments.
>>
>> On Mon, 9 Jul 2018 10:49:50 +0530 <kishon@...com> wrote:
>>
>>> Hi,
>>>
>>> On Friday 29 June 2018 02:08 PM, Kunihiko Hayashi wrote:
>>>> Add a driver for PHY interface built into USB3 controller
>>>> implemented in UniPhier SoCs.
>>>> This driver supports High-Speed PHY and Super-Speed PHY.
>>>>
>>>> Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
>>>> Signed-off-by: Motoya Tanigawa <tanigawa.motoya@...ionext.com>
>>>> Signed-off-by: Masami Hiramatsu <masami.hiramatsu@...aro.org>
>>>> ---
>>>>  drivers/phy/Kconfig                         |   1 +
>>>>  drivers/phy/Makefile                        |   1 +
>>>>  drivers/phy/socionext/Kconfig               |  12 +
>>>>  drivers/phy/socionext/Makefile              |   6 +
>>>>  drivers/phy/socionext/phy-uniphier-usb3hs.c | 422 ++++++++++++++++++++++++++++
>>>>  drivers/phy/socionext/phy-uniphier-usb3ss.c | 369 ++++++++++++++++++++++++
>>>>  6 files changed, 811 insertions(+)
>>>>  create mode 100644 drivers/phy/socionext/Kconfig
>>>>  create mode 100644 drivers/phy/socionext/Makefile
>>>>  create mode 100644 drivers/phy/socionext/phy-uniphier-usb3hs.c
>>>>  create mode 100644 drivers/phy/socionext/phy-uniphier-usb3ss.c
>>
>> (snip...)
>>
>>>> --- /dev/null
>>>> +++ b/drivers/phy/socionext/phy-uniphier-usb3hs.c
>>>> @@ -0,0 +1,422 @@
>>>> +// SPDX-License-Identifier: GPL-2.0
>>>> +/*
>>>> + * phy-uniphier-usb3hs.c - HS-PHY driver for Socionext UniPhier USB3 controller
>>>> + * Copyright 2015-2018 Socionext Inc.
>>>> + * Author:
>>>> + *	Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
>>>> + * Contributors:
>>>> + *      Motoya Tanigawa <tanigawa.motoya@...ionext.com>
>>>> + *      Masami Hiramatsu <masami.hiramatsu@...aro.org>
>>>> + */
>>>> +
>>>> +#include <linux/bitfield.h>
>>>> +#include <linux/bitops.h>
>>>> +#include <linux/clk.h>
>>>> +#include <linux/io.h>
>>>> +#include <linux/mfd/syscon.h>
>>>> +#include <linux/module.h>
>>>> +#include <linux/nvmem-consumer.h>
>>>> +#include <linux/of.h>
>>>> +#include <linux/of_platform.h>
>>>> +#include <linux/phy/phy.h>
>>>> +#include <linux/platform_device.h>
>>>> +#include <linux/reset.h>
>>>> +#include <linux/slab.h>
>>>> +
>>>> +#define HSPHY_CFG0		0x0
>>>> +#define HSPHY_CFG0_HS_I_MASK	GENMASK(31, 28)
>>>> +#define HSPHY_CFG0_HSDISC_MASK	GENMASK(27, 26)
>>>> +#define HSPHY_CFG0_SWING_MASK	GENMASK(17, 16)
>>>> +#define HSPHY_CFG0_SEL_T_MASK	GENMASK(15, 12)
>>>> +#define HSPHY_CFG0_RTERM_MASK	GENMASK(7, 6)
>>>> +#define HSPHY_CFG0_TRIMMASK	(HSPHY_CFG0_HS_I_MASK \
>>>> +				 | HSPHY_CFG0_SEL_T_MASK \
>>>> +				 | HSPHY_CFG0_RTERM_MASK)
>>>> +
>>>> +#define HSPHY_CFG1		0x4
>>>> +#define HSPHY_CFG1_DAT_EN	BIT(29)
>>>> +#define HSPHY_CFG1_ADR_EN	BIT(28)
>>>> +#define HSPHY_CFG1_ADR_MASK	GENMASK(27, 16)
>>>> +#define HSPHY_CFG1_DAT_MASK	GENMASK(23, 16)
>>>> +
>>>> +#define MAX_CLKS	3
>>>> +#define MAX_RSTS	2
>>>> +#define MAX_PHY_PARAMS	1
>>>> +
>>>> +struct uniphier_u3hsphy_param {
>>>> +	u32 addr;
>>>> +	u32 mask;
>>>> +	u32 val;
>>>> +};
>>>
>>> I'd like to avoid configure the PHY this way, since it's impossible to know
>>> which register is being configured.
>>
> 
> This way might be misunderstood.
> These HS-PHY and SS-PHY have "internal" registers, which are not memory-mapped.
> 
> And to access these internal registers, we need to specify the number
> corresponding to the register.
> 
> The "addr" in "uniphier_u3hsphy_param" is just the number of the register.
> The "mask" shows a bitfield of the register, that means one of PHY parameters.
> The "value" shows a parameter value to set to the bitfield.

What does each of these bitfields represent? Which PHY parameter does it
configure. Are they really PHY parameters or they also configure clocks/mux
etc? I would like the configurations to be more descriptive so that we get to
know at least what's getting configured here.

Thanks
Kishon