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Message-ID: <20190207121734.GA8274@ulmo>
Date: Thu, 7 Feb 2019 13:17:34 +0100
From: Thierry Reding <thierry.reding@...il.com>
To: Kishon Vijay Abraham I <kishon@...com>
Cc: Jonathan Hunter <jonathanh@...dia.com>, JC Kuo <jckuo@...dia.com>,
linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] phy: tegra: xusb: Add Tegra186 support
On Thu, Feb 07, 2019 at 05:17:59PM +0530, Kishon Vijay Abraham I wrote:
> Hi,
>
> On 25/01/19 4:55 PM, Thierry Reding wrote:
> > From: JC Kuo <jckuo@...dia.com>
> >
> > Add support for the XUSB pad controller found on Tegra186 SoCs. It is
> > mostly similar to the same IP found on earlier chips, but the number of
> > pads exposed differs, as do the programming sequences.
> >
> > Note that the DVDD_PEX, DVDD_PEX_PLL, HVDD_PEX and HVDD_PEX_PLL power
> > supplies of the XUSB pad controller require strict power sequencing and
> > are therefore controlled by the PMIC on Tegra186.
> >
> > Signed-off-by: JC Kuo <jckuo@...dia.com>
> > Signed-off-by: Thierry Reding <treding@...dia.com>
> > ---
> > MAINTAINERS | 5 +
> > drivers/phy/tegra/Makefile | 1 +
> > drivers/phy/tegra/xusb-tegra186.c | 908 ++++++++++++++++++++++++++++++
> > drivers/phy/tegra/xusb.c | 6 +
> > drivers/phy/tegra/xusb.h | 27 +
> > 5 files changed, 947 insertions(+)
> > create mode 100644 drivers/phy/tegra/xusb-tegra186.c
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index ddcdc29dfe1f..754f7e757361 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -15099,6 +15099,11 @@ M: Laxman Dewangan <ldewangan@...dia.com>
> > S: Supported
> > F: drivers/spi/spi-tegra*
> >
> > +TEGRA XUSB PADCTL DRIVER
> > +M: JC Kuo <jckuo@...dia.com>
> > +S: Supported
> > +F: drivers/phy/tegra/xusb*
> > +
> > TEHUTI ETHERNET DRIVER
> > M: Andy Gospodarek <andy@...yhouse.net>
> > L: netdev@...r.kernel.org
> > diff --git a/drivers/phy/tegra/Makefile b/drivers/phy/tegra/Makefile
> > index 898589238fd9..a93cd9a499b2 100644
> > --- a/drivers/phy/tegra/Makefile
> > +++ b/drivers/phy/tegra/Makefile
> > @@ -4,3 +4,4 @@ phy-tegra-xusb-y += xusb.o
> > 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
> > diff --git a/drivers/phy/tegra/xusb-tegra186.c b/drivers/phy/tegra/xusb-tegra186.c
> > new file mode 100644
> > index 000000000000..0dbcaddade90
> > --- /dev/null
> > +++ b/drivers/phy/tegra/xusb-tegra186.c
> > @@ -0,0 +1,908 @@
> > +/*
> > + * Copyright (c) 2016, NVIDIA CORPORATION. All rights reserved.
> > + *
> > + * This program is free software; you can redistribute it and/or modify it
> > + * under the terms and conditions of the GNU General Public License,
> > + * version 2, as published by the Free Software Foundation.
> > + *
> > + * This program is distributed in the hope it will be useful, but WITHOUT
> > + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> > + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
> > + * more details.
> > + */
>
> please use SPDX license format.
Done.
> > +
> > +#include <linux/delay.h>
> > +#include <linux/io.h>
> > +#include <linux/module.h>
> > +#include <linux/of.h>
> > +#include <linux/phy/phy.h>
> > +#include <linux/regulator/consumer.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/clk.h>
> > +#include <linux/slab.h>
> > +
> > +#include <soc/tegra/fuse.h>
> > +
> > +#include "xusb.h"
> > +
> > +/* FUSE USB_CALIB registers */
> > +#define HS_CURR_LEVEL_PADX_SHIFT(x) ((x) ? (11 + (x - 1) * 6) : 0)
> > +#define HS_CURR_LEVEL_PAD_MASK 0x3f
> > +#define HS_TERM_RANGE_ADJ_SHIFT 7
> > +#define HS_TERM_RANGE_ADJ_MASK 0xf
> > +#define HS_SQUELCH_SHIFT 29
> > +#define HS_SQUELCH_MASK 0x7
> > +
> > +#define RPD_CTRL_SHIFT 0
> > +#define RPD_CTRL_MASK 0x1f
> > +
> > +/* XUSB PADCTL registers */
> > +#define XUSB_PADCTL_USB2_PAD_MUX 0x4
> > +#define USB2_PORT_SHIFT(x) ((x) * 2)
> > +#define USB2_PORT_MASK 0x3
> > +#define PORT_XUSB 1
> > +#define HSIC_PORT_SHIFT(x) ((x) + 20)
> > +#define HSIC_PORT_MASK 0x1
> > +#define PORT_HSIC 0
> > +
> > +#define XUSB_PADCTL_USB2_PORT_CAP 0x8
> > +#define XUSB_PADCTL_SS_PORT_CAP 0xc
> > +#define PORTX_CAP_SHIFT(x) ((x) * 4)
> > +#define PORT_CAP_MASK 0x3
> > +#define PORT_CAP_DISABLED 0x0
> > +#define PORT_CAP_HOST 0x1
> > +#define PORT_CAP_DEVICE 0x2
> > +#define PORT_CAP_OTG 0x3
> > +
> > +#define XUSB_PADCTL_ELPG_PROGRAM 0x20
> > +#define USB2_PORT_WAKE_INTERRUPT_ENABLE(x) (1 << (x))
>
> Use BIT() macros here and below
Done.
> > +#define USB2_PORT_WAKEUP_EVENT(x) ( 1 << ((x) + 7))
> > +#define SS_PORT_WAKE_INTERRUPT_ENABLE(x) (1 << ((x) + 14))
> > +#define SS_PORT_WAKEUP_EVENT(x) (1 << ((x) + 21))
> > +#define USB2_HSIC_PORT_WAKE_INTERRUPT_ENABLE(x) (1 << ((x) + 28))
> > +#define USB2_HSIC_PORT_WAKEUP_EVENT(x) (1 << ((x) + 30))
> > +#define ALL_WAKE_EVENTS \
> > + (USB2_PORT_WAKEUP_EVENT(0) | USB2_PORT_WAKEUP_EVENT(1) | \
> > + USB2_PORT_WAKEUP_EVENT(2) | SS_PORT_WAKEUP_EVENT(0) | \
> > + SS_PORT_WAKEUP_EVENT(1) | SS_PORT_WAKEUP_EVENT(2) | \
> > + USB2_HSIC_PORT_WAKEUP_EVENT(0))
> > +
> > +#define XUSB_PADCTL_ELPG_PROGRAM_1 0x24
> > +#define SSPX_ELPG_CLAMP_EN(x) (1 << (0 + (x) * 3))
> > +#define SSPX_ELPG_CLAMP_EN_EARLY(x) (1 << (1 + (x) * 3))
> > +#define SSPX_ELPG_VCORE_DOWN(x) (1 << (2 + (x) * 3))
> > +
> > +#define XUSB_PADCTL_USB2_OTG_PADX_CTL0(x) (0x88 + (x) * 0x40)
> > +#define HS_CURR_LEVEL(x) ((x) & 0x3f)
> > +#define TERM_SEL (1 << 25)
> > +#define USB2_OTG_PD (1 << 26)
> > +#define USB2_OTG_PD2 (1 << 27)
> > +#define USB2_OTG_PD2_OVRD_EN (1 << 28)
> > +#define USB2_OTG_PD_ZI (1 << 29)
> > +
> > +#define XUSB_PADCTL_USB2_OTG_PADX_CTL1(x) (0x8c + (x) * 0x40)
> > +#define USB2_OTG_PD_DR (1 << 2)
> > +#define TERM_RANGE_ADJ(x) (((x) & 0xf) << 3)
> > +#define RPD_CTRL(x) (((x) & 0x1f) << 26)
> > +
> > +#define XUSB_PADCTL_USB2_BIAS_PAD_CTL0 0x284
> > +#define BIAS_PAD_PD (1 << 11)
> > +#define HS_SQUELCH_LEVEL(x) (((x) & 0x7) << 0)
> > +
> > +#define XUSB_PADCTL_USB2_BIAS_PAD_CTL1 0x288
> > +#define USB2_TRK_START_TIMER(x) (((x) & 0x7f) << 12)
> > +#define USB2_TRK_DONE_RESET_TIMER(x) (((x) & 0x7f) << 19)
> > +#define USB2_PD_TRK (1 << 26)
> > +
> > +#define XUSB_PADCTL_HSIC_PADX_CTL0(x) (0x300 + (x) * 0x20)
> > +#define HSIC_PD_TX_DATA0 (1 << 1)
> > +#define HSIC_PD_TX_STROBE (1 << 3)
> > +#define HSIC_PD_RX_DATA0 (1 << 4)
> > +#define HSIC_PD_RX_STROBE (1 << 6)
> > +#define HSIC_PD_ZI_DATA0 (1 << 7)
> > +#define HSIC_PD_ZI_STROBE (1 << 9)
> > +#define HSIC_RPD_DATA0 (1 << 13)
> > +#define HSIC_RPD_STROBE (1 << 15)
> > +#define HSIC_RPU_DATA0 (1 << 16)
> > +#define HSIC_RPU_STROBE (1 << 18)
> > +
> > +#define XUSB_PADCTL_HSIC_PAD_TRK_CTL0 (0x340)
>
> unnecessary ().
Done.
> > +#define HSIC_TRK_START_TIMER(x) (((x) & 0x7f) << 5)
> > +#define HSIC_TRK_DONE_RESET_TIMER(x) (((x) & 0x7f) << 12)
> > +#define HSIC_PD_TRK (1 << 19)
> > +
> > +#define USB2_VBUS_ID (0x360)
>
> here too..
Done.
> > +#define VBUS_OVERRIDE (1 << 14)
> > +#define ID_OVERRIDE(x) (((x) & 0xf) << 18)
> > +#define ID_OVERRIDE_FLOATING ID_OVERRIDE(8)
> > +#define ID_OVERRIDE_GROUNDED ID_OVERRIDE(0)
> > +
> > +#define TEGRA186_LANE(_name, _offset, _shift, _mask, _type) \
> > + { \
> > + .name = _name, \
> > + .offset = _offset, \
> > + .shift = _shift, \
> > + .mask = _mask, \
> > + .num_funcs = ARRAY_SIZE(tegra186_##_type##_functions), \
> > + .funcs = tegra186_##_type##_functions, \
> > + }
> > +
> > +struct tegra_xusb_fuse_calibration {
> > + u32 *hs_curr_level;
> > + u32 hs_squelch;
> > + u32 hs_term_range_adj;
> > + u32 rpd_ctrl;
> > +};
> > +
> > +struct tegra186_xusb_padctl {
> > + struct tegra_xusb_padctl base;
> > +
> > + struct tegra_xusb_fuse_calibration calib;
> > +
> > + /* UTMI bias and tracking */
> > + struct clk *usb2_trk_clk;
> > + unsigned int bias_pad_enable;
> > +};
> > +
> > +static inline struct tegra186_xusb_padctl *
> > +to_tegra186_xusb_padctl(struct tegra_xusb_padctl *padctl)
> > +{
> > + return container_of(padctl, struct tegra186_xusb_padctl, base);
> > +}
> > +
> > +/* USB 2.0 UTMI PHY support */
> > +static struct tegra_xusb_lane *
> > +tegra186_usb2_lane_probe(struct tegra_xusb_pad *pad, struct device_node *np,
> > + unsigned int index)
> > +{
> > + struct tegra_xusb_usb2_lane *usb2;
> > + int err;
> > +
> > + usb2 = kzalloc(sizeof(*usb2), GFP_KERNEL);
> > + if (!usb2)
> > + return ERR_PTR(-ENOMEM);
> > +
> > + INIT_LIST_HEAD(&usb2->base.list);
> > + usb2->base.soc = &pad->soc->lanes[index];
> > + usb2->base.index = index;
> > + usb2->base.pad = pad;
> > + usb2->base.np = np;
> > +
> > + err = tegra_xusb_lane_parse_dt(&usb2->base, np);
> > + if (err < 0) {
> > + kfree(usb2);
> > + return ERR_PTR(err);
> > + }
> > +
> > + return &usb2->base;
> > +}
> > +
> > +static void tegra186_usb2_lane_remove(struct tegra_xusb_lane *lane)
> > +{
> > + struct tegra_xusb_usb2_lane *usb2 = to_usb2_lane(lane);
> > +
> > + kfree(usb2);
> > +}
> > +
> > +static const struct tegra_xusb_lane_ops tegra186_usb2_lane_ops = {
> > + .probe = tegra186_usb2_lane_probe,
> > + .remove = tegra186_usb2_lane_remove,
> > +};
> > +
> > +static void tegra186_utmi_bias_pad_power_on(struct tegra_xusb_padctl *padctl)
> > +{
> > + struct tegra186_xusb_padctl *priv = to_tegra186_xusb_padctl(padctl);
> > + struct device *dev = padctl->dev;
> > + u32 value;
> > + int err;
> > +
> > + mutex_lock(&padctl->lock);
> > +
> > + if (priv->bias_pad_enable++ > 0) {
> > + mutex_unlock(&padctl->lock);
> > + return;
> > + }
> > +
> > + err = clk_prepare_enable(priv->usb2_trk_clk);
> > + if (err < 0)
> > + dev_warn(dev, "failed to enable USB2 trk clock: %d\n", err);
> > +
> > + value = padctl_readl(padctl, XUSB_PADCTL_USB2_BIAS_PAD_CTL1);
> > + value &= ~USB2_TRK_START_TIMER(~0);
> > + value |= USB2_TRK_START_TIMER(0x1e);
> > + value &= ~USB2_TRK_DONE_RESET_TIMER(~0);
> > + value |= USB2_TRK_DONE_RESET_TIMER(0xa);
> > + padctl_writel(padctl, value, XUSB_PADCTL_USB2_BIAS_PAD_CTL1);
> > +
> > + value = padctl_readl(padctl, XUSB_PADCTL_USB2_BIAS_PAD_CTL0);
> > + value &= ~BIAS_PAD_PD;
> > + value &= ~HS_SQUELCH_LEVEL(~0);
> > + value |= HS_SQUELCH_LEVEL(priv->calib.hs_squelch);
> > + padctl_writel(padctl, value, XUSB_PADCTL_USB2_BIAS_PAD_CTL0);
> > +
> > + udelay(1);
> > +
> > + value = padctl_readl(padctl, XUSB_PADCTL_USB2_BIAS_PAD_CTL1);
> > + value &= ~USB2_PD_TRK;
> > + padctl_writel(padctl, value, XUSB_PADCTL_USB2_BIAS_PAD_CTL1);
> > +
> > + mutex_unlock(&padctl->lock);
> > +}
> > +
> > +static void tegra186_utmi_bias_pad_power_off(struct tegra_xusb_padctl *padctl)
> > +{
> > + struct tegra186_xusb_padctl *priv = to_tegra186_xusb_padctl(padctl);
> > + u32 value;
> > +
> > + mutex_lock(&padctl->lock);
> > +
> > + if (WARN_ON(priv->bias_pad_enable == 0)) {
> > + mutex_unlock(&padctl->lock);
> > + return;
> > + }
> > +
> > + if (--priv->bias_pad_enable > 0) {
> > + mutex_unlock(&padctl->lock);
> > + return;
> > + }
> > +
> > + value = padctl_readl(padctl, XUSB_PADCTL_USB2_BIAS_PAD_CTL1);
> > + value |= USB2_PD_TRK;
> > + padctl_writel(padctl, value, XUSB_PADCTL_USB2_BIAS_PAD_CTL1);
> > +
> > + clk_disable_unprepare(priv->usb2_trk_clk);
> > +
> > + mutex_unlock(&padctl->lock);
> > +}
> > +
> > +void tegra_phy_xusb_utmi_pad_power_on(struct phy *phy)
> > +{
> > + struct tegra_xusb_lane *lane = phy_get_drvdata(phy);
> > + struct tegra_xusb_padctl *padctl = lane->pad->padctl;
> > + struct tegra_xusb_usb2_port *port;
> > + struct device *dev = padctl->dev;
> > + unsigned int index = lane->index;
> > + u32 value;
> > +
> > + if (!phy)
> > + return;
> > +
> > + port = tegra_xusb_find_usb2_port(padctl, index);
> > + if (!port) {
> > + dev_err(dev, "no port found for USB2 lane %u\n", index);
> > + return;
> > + }
> > +
> > + tegra186_utmi_bias_pad_power_on(padctl);
> > +
> > + udelay(2);
> > +
> > + value = padctl_readl(padctl, XUSB_PADCTL_USB2_OTG_PADX_CTL0(index));
> > + value &= ~USB2_OTG_PD;
> > + padctl_writel(padctl, value, XUSB_PADCTL_USB2_OTG_PADX_CTL0(index));
> > +
> > + value = padctl_readl(padctl, XUSB_PADCTL_USB2_OTG_PADX_CTL1(index));
> > + value &= ~USB2_OTG_PD_DR;
> > + padctl_writel(padctl, value, XUSB_PADCTL_USB2_OTG_PADX_CTL1(index));
> > +}
> > +
> > +void tegra_phy_xusb_utmi_pad_power_down(struct phy *phy)
> > +{
> > + struct tegra_xusb_lane *lane = phy_get_drvdata(phy);
> > + struct tegra_xusb_padctl *padctl = lane->pad->padctl;
> > + unsigned int index = lane->index;
> > + u32 value;
> > +
> > + if (!phy)
> > + return;
> > +
> > + value = padctl_readl(padctl, XUSB_PADCTL_USB2_OTG_PADX_CTL0(index));
> > + value |= USB2_OTG_PD;
> > + padctl_writel(padctl, value, XUSB_PADCTL_USB2_OTG_PADX_CTL0(index));
> > +
> > + value = padctl_readl(padctl, XUSB_PADCTL_USB2_OTG_PADX_CTL1(index));
> > + value |= USB2_OTG_PD_DR;
> > + padctl_writel(padctl, value, XUSB_PADCTL_USB2_OTG_PADX_CTL1(index));
> > +
> > + udelay(2);
> > +
> > + tegra186_utmi_bias_pad_power_off(padctl);
> > +}
> > +
> > +static int tegra186_utmi_phy_power_on(struct phy *phy)
> > +{
> > + struct tegra_xusb_lane *lane = phy_get_drvdata(phy);
> > + struct tegra_xusb_usb2_lane *usb2 = to_usb2_lane(lane);
> > + struct tegra_xusb_padctl *padctl = lane->pad->padctl;
> > + struct tegra186_xusb_padctl *priv = to_tegra186_xusb_padctl(padctl);
> > + struct tegra_xusb_usb2_port *port;
> > + unsigned int index = lane->index;
> > + struct device *dev = padctl->dev;
> > + u32 value;
> > +
> > + port = tegra_xusb_find_usb2_port(padctl, index);
> > + if (!port) {
> > + dev_err(dev, "no port found for USB2 lane %u\n", index);
> > + return -ENODEV;
> > + }
> > +
> > + value = padctl_readl(padctl, XUSB_PADCTL_USB2_PAD_MUX);
> > + value &= ~(USB2_PORT_MASK << USB2_PORT_SHIFT(index));
> > + value |= (PORT_XUSB << USB2_PORT_SHIFT(index));
> > + padctl_writel(padctl, value, XUSB_PADCTL_USB2_PAD_MUX);
> > +
> > + value = padctl_readl(padctl, XUSB_PADCTL_USB2_PORT_CAP);
> > + value &= ~(PORT_CAP_MASK << PORTX_CAP_SHIFT(index));
> > +
> > + if (port->mode == USB_DR_MODE_UNKNOWN)
> > + value |= (PORT_CAP_DISABLED << PORTX_CAP_SHIFT(index));
> > + else if (port->mode == USB_DR_MODE_PERIPHERAL)
> > + value |= (PORT_CAP_DEVICE << PORTX_CAP_SHIFT(index));
> > + else if (port->mode == USB_DR_MODE_HOST)
> > + value |= (PORT_CAP_HOST << PORTX_CAP_SHIFT(index));
> > + else if (port->mode == USB_DR_MODE_OTG)
> > + value |= (PORT_CAP_OTG << PORTX_CAP_SHIFT(index));
> > +
> > + padctl_writel(padctl, value, XUSB_PADCTL_USB2_PORT_CAP);
> > +
> > + value = padctl_readl(padctl, XUSB_PADCTL_USB2_OTG_PADX_CTL0(index));
> > + value &= ~USB2_OTG_PD_ZI;
> > + value |= TERM_SEL;
> > + value &= ~HS_CURR_LEVEL(~0);
> > +
> > + /* TODO hs_curr_level_offset support */
>
> What is TODO here?
Nothing. hs_curr_level_offset support is clearly implemented below, so
I've removed the stale comment.
> > + if (usb2->hs_curr_level_offset) {
> > + int hs_current_level;
> > +
> > + hs_current_level = (int)priv->calib.hs_curr_level[index] +
> > + usb2->hs_curr_level_offset;
> > +
> > + if (hs_current_level < 0)
> > + hs_current_level = 0;
> > + if (hs_current_level > 0x3f)
> > + hs_current_level = 0x3f;
> > +
> > + value |= HS_CURR_LEVEL(hs_current_level);
> > + } else {
> > + value |= HS_CURR_LEVEL(priv->calib.hs_curr_level[index]);
> > + }
> > +
> > + padctl_writel(padctl, value, XUSB_PADCTL_USB2_OTG_PADX_CTL0(index));
> > +
> > + value = padctl_readl(padctl, XUSB_PADCTL_USB2_OTG_PADX_CTL1(index));
> > + value &= ~TERM_RANGE_ADJ(~0);
> > + value |= TERM_RANGE_ADJ(priv->calib.hs_term_range_adj);
> > + value &= ~RPD_CTRL(~0);
> > + value |= RPD_CTRL(priv->calib.rpd_ctrl);
> > + padctl_writel(padctl, value, XUSB_PADCTL_USB2_OTG_PADX_CTL1(index));
> > +
> > + /* TODO: pad power saving */
> > + tegra_phy_xusb_utmi_pad_power_on(phy);
> > + return 0;
> > +}
> > +
> > +static int tegra186_utmi_phy_power_off(struct phy *phy)
> > +{
> > + /* TODO: pad power saving */
> > + tegra_phy_xusb_utmi_pad_power_down(phy);
> > +
> > + return 0;
> > +}
> > +
> > +static int tegra186_utmi_phy_init(struct phy *phy)
> > +{
> > + struct tegra_xusb_lane *lane = phy_get_drvdata(phy);
> > + struct tegra_xusb_padctl *padctl = lane->pad->padctl;
> > + struct tegra_xusb_usb2_port *port;
> > + unsigned int index = lane->index;
> > + struct device *dev = padctl->dev;
> > + int err;
> > +
> > + port = tegra_xusb_find_usb2_port(padctl, index);
>
> I would prefer if this entire driver is rewritten without using xusb library.
I don't think that would be possible without duplicating most of the
code in xusb.c into each of xusb-tegra124.c, xusb-tegra210.c and
xusb-tegra186.c.
> Ideally you shouldn't have to traverse a list to configure the PHY. phy_get
> already does that for you. It should be straight forward to get "port" from "phy".
There's a subtle difference here between port and PHY. The "phy" that
we're initializing here is actually the "lane" in Tegra terms. Each pad
on Tegra (typically USB, PCIe, SATA, ...) can have multiple lanes, each
of which can be muxed to a specific function.
Ports are a separate abstraction that is used to represent the physical
connectors on a board. This is different from the lane.
> I think xusb is making it more complicated than it has to be.
I understand that it may seem that way, but a lot of thought went into
abstracting this in order to cover the various scenarios that we can run
into, and to be able to unify this across multiple chips.
A lot of this infrastructure is also there to make sure the device tree
is actually consistent. So the indirections and abstractions not only
serve to wrap PHYs and ports into objects that are easy to work with but
also to validate that the device tree adheres to the device tree
bindings.
Thierry
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