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

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Date:   Wed, 11 Jul 2018 21:05:14 +0900
From:   Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
To:     Kishon Vijay Abraham I <kishon@...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

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.


> I see. 
> In order to know which register is set, I'll add definitions for address
> and mask.
> And I think the driver might have functions for each SoC to configure
> the registers instead of uniphier_u3hsphy_param.

Then, I think it's sufficient to define a macro with a meaningful label for
each bitfield, and PHY parameters are expressed like that.

  { 10, FOO_BAR_MODE, 0x2 }, /* set 2 to FOO_BAR_MODE in register 10 */

In this case, we need to shift "value" according to "mask".

Thank you,

---
Best Regards,
Kunihiko Hayashi