linux/drivers/clk/clk-xgene.c
Thomas Gleixner 1a59d1b8e0 treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156
Based on 1 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license as published by
  the free software foundation either version 2 of the license or at
  your option any later version this program is distributed in the
  hope that 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 you
  should have received a copy of the gnu general public license along
  with this program if not write to the free software foundation inc
  59 temple place suite 330 boston ma 02111 1307 usa

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 1334 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070033.113240726@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-05-30 11:26:35 -07:00

748 lines
19 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/*
* clk-xgene.c - AppliedMicro X-Gene Clock Interface
*
* Copyright (c) 2013, Applied Micro Circuits Corporation
* Author: Loc Ho <lho@apm.com>
*/
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/clkdev.h>
#include <linux/clk-provider.h>
#include <linux/of_address.h>
/* Register SCU_PCPPLL bit fields */
#define N_DIV_RD(src) ((src) & 0x000001ff)
#define SC_N_DIV_RD(src) ((src) & 0x0000007f)
#define SC_OUTDIV2(src) (((src) & 0x00000100) >> 8)
/* Register SCU_SOCPLL bit fields */
#define CLKR_RD(src) (((src) & 0x07000000)>>24)
#define CLKOD_RD(src) (((src) & 0x00300000)>>20)
#define REGSPEC_RESET_F1_MASK 0x00010000
#define CLKF_RD(src) (((src) & 0x000001ff))
#define XGENE_CLK_DRIVER_VER "0.1"
static DEFINE_SPINLOCK(clk_lock);
static inline u32 xgene_clk_read(void __iomem *csr)
{
return readl_relaxed(csr);
}
static inline void xgene_clk_write(u32 data, void __iomem *csr)
{
writel_relaxed(data, csr);
}
/* PLL Clock */
enum xgene_pll_type {
PLL_TYPE_PCP = 0,
PLL_TYPE_SOC = 1,
};
struct xgene_clk_pll {
struct clk_hw hw;
void __iomem *reg;
spinlock_t *lock;
u32 pll_offset;
enum xgene_pll_type type;
int version;
};
#define to_xgene_clk_pll(_hw) container_of(_hw, struct xgene_clk_pll, hw)
static int xgene_clk_pll_is_enabled(struct clk_hw *hw)
{
struct xgene_clk_pll *pllclk = to_xgene_clk_pll(hw);
u32 data;
data = xgene_clk_read(pllclk->reg + pllclk->pll_offset);
pr_debug("%s pll %s\n", clk_hw_get_name(hw),
data & REGSPEC_RESET_F1_MASK ? "disabled" : "enabled");
return data & REGSPEC_RESET_F1_MASK ? 0 : 1;
}
static unsigned long xgene_clk_pll_recalc_rate(struct clk_hw *hw,
unsigned long parent_rate)
{
struct xgene_clk_pll *pllclk = to_xgene_clk_pll(hw);
unsigned long fref;
unsigned long fvco;
u32 pll;
u32 nref;
u32 nout;
u32 nfb;
pll = xgene_clk_read(pllclk->reg + pllclk->pll_offset);
if (pllclk->version <= 1) {
if (pllclk->type == PLL_TYPE_PCP) {
/*
* PLL VCO = Reference clock * NF
* PCP PLL = PLL_VCO / 2
*/
nout = 2;
fvco = parent_rate * (N_DIV_RD(pll) + 4);
} else {
/*
* Fref = Reference Clock / NREF;
* Fvco = Fref * NFB;
* Fout = Fvco / NOUT;
*/
nref = CLKR_RD(pll) + 1;
nout = CLKOD_RD(pll) + 1;
nfb = CLKF_RD(pll);
fref = parent_rate / nref;
fvco = fref * nfb;
}
} else {
/*
* fvco = Reference clock * FBDIVC
* PLL freq = fvco / NOUT
*/
nout = SC_OUTDIV2(pll) ? 2 : 3;
fvco = parent_rate * SC_N_DIV_RD(pll);
}
pr_debug("%s pll recalc rate %ld parent %ld version %d\n",
clk_hw_get_name(hw), fvco / nout, parent_rate,
pllclk->version);
return fvco / nout;
}
static const struct clk_ops xgene_clk_pll_ops = {
.is_enabled = xgene_clk_pll_is_enabled,
.recalc_rate = xgene_clk_pll_recalc_rate,
};
static struct clk *xgene_register_clk_pll(struct device *dev,
const char *name, const char *parent_name,
unsigned long flags, void __iomem *reg, u32 pll_offset,
u32 type, spinlock_t *lock, int version)
{
struct xgene_clk_pll *apmclk;
struct clk *clk;
struct clk_init_data init;
/* allocate the APM clock structure */
apmclk = kzalloc(sizeof(*apmclk), GFP_KERNEL);
if (!apmclk)
return ERR_PTR(-ENOMEM);
init.name = name;
init.ops = &xgene_clk_pll_ops;
init.flags = flags;
init.parent_names = parent_name ? &parent_name : NULL;
init.num_parents = parent_name ? 1 : 0;
apmclk->version = version;
apmclk->reg = reg;
apmclk->lock = lock;
apmclk->pll_offset = pll_offset;
apmclk->type = type;
apmclk->hw.init = &init;
/* Register the clock */
clk = clk_register(dev, &apmclk->hw);
if (IS_ERR(clk)) {
pr_err("%s: could not register clk %s\n", __func__, name);
kfree(apmclk);
return NULL;
}
return clk;
}
static int xgene_pllclk_version(struct device_node *np)
{
if (of_device_is_compatible(np, "apm,xgene-socpll-clock"))
return 1;
if (of_device_is_compatible(np, "apm,xgene-pcppll-clock"))
return 1;
return 2;
}
static void xgene_pllclk_init(struct device_node *np, enum xgene_pll_type pll_type)
{
const char *clk_name = np->full_name;
struct clk *clk;
void __iomem *reg;
int version = xgene_pllclk_version(np);
reg = of_iomap(np, 0);
if (!reg) {
pr_err("Unable to map CSR register for %pOF\n", np);
return;
}
of_property_read_string(np, "clock-output-names", &clk_name);
clk = xgene_register_clk_pll(NULL,
clk_name, of_clk_get_parent_name(np, 0),
0, reg, 0, pll_type, &clk_lock,
version);
if (!IS_ERR(clk)) {
of_clk_add_provider(np, of_clk_src_simple_get, clk);
clk_register_clkdev(clk, clk_name, NULL);
pr_debug("Add %s clock PLL\n", clk_name);
}
}
static void xgene_socpllclk_init(struct device_node *np)
{
xgene_pllclk_init(np, PLL_TYPE_SOC);
}
static void xgene_pcppllclk_init(struct device_node *np)
{
xgene_pllclk_init(np, PLL_TYPE_PCP);
}
/**
* struct xgene_clk_pmd - PMD clock
*
* @hw: handle between common and hardware-specific interfaces
* @reg: register containing the fractional scale multiplier (scaler)
* @shift: shift to the unit bit field
* @denom: 1/denominator unit
* @lock: register lock
* Flags:
* XGENE_CLK_PMD_SCALE_INVERTED - By default the scaler is the value read
* from the register plus one. For example,
* 0 for (0 + 1) / denom,
* 1 for (1 + 1) / denom and etc.
* If this flag is set, it is
* 0 for (denom - 0) / denom,
* 1 for (denom - 1) / denom and etc.
*
*/
struct xgene_clk_pmd {
struct clk_hw hw;
void __iomem *reg;
u8 shift;
u32 mask;
u64 denom;
u32 flags;
spinlock_t *lock;
};
#define to_xgene_clk_pmd(_hw) container_of(_hw, struct xgene_clk_pmd, hw)
#define XGENE_CLK_PMD_SCALE_INVERTED BIT(0)
#define XGENE_CLK_PMD_SHIFT 8
#define XGENE_CLK_PMD_WIDTH 3
static unsigned long xgene_clk_pmd_recalc_rate(struct clk_hw *hw,
unsigned long parent_rate)
{
struct xgene_clk_pmd *fd = to_xgene_clk_pmd(hw);
unsigned long flags = 0;
u64 ret, scale;
u32 val;
if (fd->lock)
spin_lock_irqsave(fd->lock, flags);
else
__acquire(fd->lock);
val = readl(fd->reg);
if (fd->lock)
spin_unlock_irqrestore(fd->lock, flags);
else
__release(fd->lock);
ret = (u64)parent_rate;
scale = (val & fd->mask) >> fd->shift;
if (fd->flags & XGENE_CLK_PMD_SCALE_INVERTED)
scale = fd->denom - scale;
else
scale++;
/* freq = parent_rate * scaler / denom */
do_div(ret, fd->denom);
ret *= scale;
if (ret == 0)
ret = (u64)parent_rate;
return ret;
}
static long xgene_clk_pmd_round_rate(struct clk_hw *hw, unsigned long rate,
unsigned long *parent_rate)
{
struct xgene_clk_pmd *fd = to_xgene_clk_pmd(hw);
u64 ret, scale;
if (!rate || rate >= *parent_rate)
return *parent_rate;
/* freq = parent_rate * scaler / denom */
ret = rate * fd->denom;
scale = DIV_ROUND_UP_ULL(ret, *parent_rate);
ret = (u64)*parent_rate * scale;
do_div(ret, fd->denom);
return ret;
}
static int xgene_clk_pmd_set_rate(struct clk_hw *hw, unsigned long rate,
unsigned long parent_rate)
{
struct xgene_clk_pmd *fd = to_xgene_clk_pmd(hw);
unsigned long flags = 0;
u64 scale, ret;
u32 val;
/*
* Compute the scaler:
*
* freq = parent_rate * scaler / denom, or
* scaler = freq * denom / parent_rate
*/
ret = rate * fd->denom;
scale = DIV_ROUND_UP_ULL(ret, (u64)parent_rate);
/* Check if inverted */
if (fd->flags & XGENE_CLK_PMD_SCALE_INVERTED)
scale = fd->denom - scale;
else
scale--;
if (fd->lock)
spin_lock_irqsave(fd->lock, flags);
else
__acquire(fd->lock);
val = readl(fd->reg);
val &= ~fd->mask;
val |= (scale << fd->shift);
writel(val, fd->reg);
if (fd->lock)
spin_unlock_irqrestore(fd->lock, flags);
else
__release(fd->lock);
return 0;
}
static const struct clk_ops xgene_clk_pmd_ops = {
.recalc_rate = xgene_clk_pmd_recalc_rate,
.round_rate = xgene_clk_pmd_round_rate,
.set_rate = xgene_clk_pmd_set_rate,
};
static struct clk *
xgene_register_clk_pmd(struct device *dev,
const char *name, const char *parent_name,
unsigned long flags, void __iomem *reg, u8 shift,
u8 width, u64 denom, u32 clk_flags, spinlock_t *lock)
{
struct xgene_clk_pmd *fd;
struct clk_init_data init;
struct clk *clk;
fd = kzalloc(sizeof(*fd), GFP_KERNEL);
if (!fd)
return ERR_PTR(-ENOMEM);
init.name = name;
init.ops = &xgene_clk_pmd_ops;
init.flags = flags;
init.parent_names = parent_name ? &parent_name : NULL;
init.num_parents = parent_name ? 1 : 0;
fd->reg = reg;
fd->shift = shift;
fd->mask = (BIT(width) - 1) << shift;
fd->denom = denom;
fd->flags = clk_flags;
fd->lock = lock;
fd->hw.init = &init;
clk = clk_register(dev, &fd->hw);
if (IS_ERR(clk)) {
pr_err("%s: could not register clk %s\n", __func__, name);
kfree(fd);
return NULL;
}
return clk;
}
static void xgene_pmdclk_init(struct device_node *np)
{
const char *clk_name = np->full_name;
void __iomem *csr_reg;
struct resource res;
struct clk *clk;
u64 denom;
u32 flags = 0;
int rc;
/* Check if the entry is disabled */
if (!of_device_is_available(np))
return;
/* Parse the DTS register for resource */
rc = of_address_to_resource(np, 0, &res);
if (rc != 0) {
pr_err("no DTS register for %pOF\n", np);
return;
}
csr_reg = of_iomap(np, 0);
if (!csr_reg) {
pr_err("Unable to map resource for %pOF\n", np);
return;
}
of_property_read_string(np, "clock-output-names", &clk_name);
denom = BIT(XGENE_CLK_PMD_WIDTH);
flags |= XGENE_CLK_PMD_SCALE_INVERTED;
clk = xgene_register_clk_pmd(NULL, clk_name,
of_clk_get_parent_name(np, 0), 0,
csr_reg, XGENE_CLK_PMD_SHIFT,
XGENE_CLK_PMD_WIDTH, denom,
flags, &clk_lock);
if (!IS_ERR(clk)) {
of_clk_add_provider(np, of_clk_src_simple_get, clk);
clk_register_clkdev(clk, clk_name, NULL);
pr_debug("Add %s clock\n", clk_name);
} else {
if (csr_reg)
iounmap(csr_reg);
}
}
/* IP Clock */
struct xgene_dev_parameters {
void __iomem *csr_reg; /* CSR for IP clock */
u32 reg_clk_offset; /* Offset to clock enable CSR */
u32 reg_clk_mask; /* Mask bit for clock enable */
u32 reg_csr_offset; /* Offset to CSR reset */
u32 reg_csr_mask; /* Mask bit for disable CSR reset */
void __iomem *divider_reg; /* CSR for divider */
u32 reg_divider_offset; /* Offset to divider register */
u32 reg_divider_shift; /* Bit shift to divider field */
u32 reg_divider_width; /* Width of the bit to divider field */
};
struct xgene_clk {
struct clk_hw hw;
spinlock_t *lock;
struct xgene_dev_parameters param;
};
#define to_xgene_clk(_hw) container_of(_hw, struct xgene_clk, hw)
static int xgene_clk_enable(struct clk_hw *hw)
{
struct xgene_clk *pclk = to_xgene_clk(hw);
unsigned long flags = 0;
u32 data;
if (pclk->lock)
spin_lock_irqsave(pclk->lock, flags);
if (pclk->param.csr_reg) {
pr_debug("%s clock enabled\n", clk_hw_get_name(hw));
/* First enable the clock */
data = xgene_clk_read(pclk->param.csr_reg +
pclk->param.reg_clk_offset);
data |= pclk->param.reg_clk_mask;
xgene_clk_write(data, pclk->param.csr_reg +
pclk->param.reg_clk_offset);
pr_debug("%s clk offset 0x%08X mask 0x%08X value 0x%08X\n",
clk_hw_get_name(hw),
pclk->param.reg_clk_offset, pclk->param.reg_clk_mask,
data);
/* Second enable the CSR */
data = xgene_clk_read(pclk->param.csr_reg +
pclk->param.reg_csr_offset);
data &= ~pclk->param.reg_csr_mask;
xgene_clk_write(data, pclk->param.csr_reg +
pclk->param.reg_csr_offset);
pr_debug("%s csr offset 0x%08X mask 0x%08X value 0x%08X\n",
clk_hw_get_name(hw),
pclk->param.reg_csr_offset, pclk->param.reg_csr_mask,
data);
}
if (pclk->lock)
spin_unlock_irqrestore(pclk->lock, flags);
return 0;
}
static void xgene_clk_disable(struct clk_hw *hw)
{
struct xgene_clk *pclk = to_xgene_clk(hw);
unsigned long flags = 0;
u32 data;
if (pclk->lock)
spin_lock_irqsave(pclk->lock, flags);
if (pclk->param.csr_reg) {
pr_debug("%s clock disabled\n", clk_hw_get_name(hw));
/* First put the CSR in reset */
data = xgene_clk_read(pclk->param.csr_reg +
pclk->param.reg_csr_offset);
data |= pclk->param.reg_csr_mask;
xgene_clk_write(data, pclk->param.csr_reg +
pclk->param.reg_csr_offset);
/* Second disable the clock */
data = xgene_clk_read(pclk->param.csr_reg +
pclk->param.reg_clk_offset);
data &= ~pclk->param.reg_clk_mask;
xgene_clk_write(data, pclk->param.csr_reg +
pclk->param.reg_clk_offset);
}
if (pclk->lock)
spin_unlock_irqrestore(pclk->lock, flags);
}
static int xgene_clk_is_enabled(struct clk_hw *hw)
{
struct xgene_clk *pclk = to_xgene_clk(hw);
u32 data = 0;
if (pclk->param.csr_reg) {
pr_debug("%s clock checking\n", clk_hw_get_name(hw));
data = xgene_clk_read(pclk->param.csr_reg +
pclk->param.reg_clk_offset);
pr_debug("%s clock is %s\n", clk_hw_get_name(hw),
data & pclk->param.reg_clk_mask ? "enabled" :
"disabled");
}
if (!pclk->param.csr_reg)
return 1;
return data & pclk->param.reg_clk_mask ? 1 : 0;
}
static unsigned long xgene_clk_recalc_rate(struct clk_hw *hw,
unsigned long parent_rate)
{
struct xgene_clk *pclk = to_xgene_clk(hw);
u32 data;
if (pclk->param.divider_reg) {
data = xgene_clk_read(pclk->param.divider_reg +
pclk->param.reg_divider_offset);
data >>= pclk->param.reg_divider_shift;
data &= (1 << pclk->param.reg_divider_width) - 1;
pr_debug("%s clock recalc rate %ld parent %ld\n",
clk_hw_get_name(hw),
parent_rate / data, parent_rate);
return parent_rate / data;
} else {
pr_debug("%s clock recalc rate %ld parent %ld\n",
clk_hw_get_name(hw), parent_rate, parent_rate);
return parent_rate;
}
}
static int xgene_clk_set_rate(struct clk_hw *hw, unsigned long rate,
unsigned long parent_rate)
{
struct xgene_clk *pclk = to_xgene_clk(hw);
unsigned long flags = 0;
u32 data;
u32 divider;
u32 divider_save;
if (pclk->lock)
spin_lock_irqsave(pclk->lock, flags);
if (pclk->param.divider_reg) {
/* Let's compute the divider */
if (rate > parent_rate)
rate = parent_rate;
divider_save = divider = parent_rate / rate; /* Rounded down */
divider &= (1 << pclk->param.reg_divider_width) - 1;
divider <<= pclk->param.reg_divider_shift;
/* Set new divider */
data = xgene_clk_read(pclk->param.divider_reg +
pclk->param.reg_divider_offset);
data &= ~(((1 << pclk->param.reg_divider_width) - 1)
<< pclk->param.reg_divider_shift);
data |= divider;
xgene_clk_write(data, pclk->param.divider_reg +
pclk->param.reg_divider_offset);
pr_debug("%s clock set rate %ld\n", clk_hw_get_name(hw),
parent_rate / divider_save);
} else {
divider_save = 1;
}
if (pclk->lock)
spin_unlock_irqrestore(pclk->lock, flags);
return parent_rate / divider_save;
}
static long xgene_clk_round_rate(struct clk_hw *hw, unsigned long rate,
unsigned long *prate)
{
struct xgene_clk *pclk = to_xgene_clk(hw);
unsigned long parent_rate = *prate;
u32 divider;
if (pclk->param.divider_reg) {
/* Let's compute the divider */
if (rate > parent_rate)
rate = parent_rate;
divider = parent_rate / rate; /* Rounded down */
} else {
divider = 1;
}
return parent_rate / divider;
}
static const struct clk_ops xgene_clk_ops = {
.enable = xgene_clk_enable,
.disable = xgene_clk_disable,
.is_enabled = xgene_clk_is_enabled,
.recalc_rate = xgene_clk_recalc_rate,
.set_rate = xgene_clk_set_rate,
.round_rate = xgene_clk_round_rate,
};
static struct clk *xgene_register_clk(struct device *dev,
const char *name, const char *parent_name,
struct xgene_dev_parameters *parameters, spinlock_t *lock)
{
struct xgene_clk *apmclk;
struct clk *clk;
struct clk_init_data init;
int rc;
/* allocate the APM clock structure */
apmclk = kzalloc(sizeof(*apmclk), GFP_KERNEL);
if (!apmclk)
return ERR_PTR(-ENOMEM);
init.name = name;
init.ops = &xgene_clk_ops;
init.flags = 0;
init.parent_names = parent_name ? &parent_name : NULL;
init.num_parents = parent_name ? 1 : 0;
apmclk->lock = lock;
apmclk->hw.init = &init;
apmclk->param = *parameters;
/* Register the clock */
clk = clk_register(dev, &apmclk->hw);
if (IS_ERR(clk)) {
pr_err("%s: could not register clk %s\n", __func__, name);
kfree(apmclk);
return clk;
}
/* Register the clock for lookup */
rc = clk_register_clkdev(clk, name, NULL);
if (rc != 0) {
pr_err("%s: could not register lookup clk %s\n",
__func__, name);
}
return clk;
}
static void __init xgene_devclk_init(struct device_node *np)
{
const char *clk_name = np->full_name;
struct clk *clk;
struct resource res;
int rc;
struct xgene_dev_parameters parameters;
int i;
/* Check if the entry is disabled */
if (!of_device_is_available(np))
return;
/* Parse the DTS register for resource */
parameters.csr_reg = NULL;
parameters.divider_reg = NULL;
for (i = 0; i < 2; i++) {
void __iomem *map_res;
rc = of_address_to_resource(np, i, &res);
if (rc != 0) {
if (i == 0) {
pr_err("no DTS register for %pOF\n", np);
return;
}
break;
}
map_res = of_iomap(np, i);
if (!map_res) {
pr_err("Unable to map resource %d for %pOF\n", i, np);
goto err;
}
if (strcmp(res.name, "div-reg") == 0)
parameters.divider_reg = map_res;
else /* if (strcmp(res->name, "csr-reg") == 0) */
parameters.csr_reg = map_res;
}
if (of_property_read_u32(np, "csr-offset", &parameters.reg_csr_offset))
parameters.reg_csr_offset = 0;
if (of_property_read_u32(np, "csr-mask", &parameters.reg_csr_mask))
parameters.reg_csr_mask = 0xF;
if (of_property_read_u32(np, "enable-offset",
&parameters.reg_clk_offset))
parameters.reg_clk_offset = 0x8;
if (of_property_read_u32(np, "enable-mask", &parameters.reg_clk_mask))
parameters.reg_clk_mask = 0xF;
if (of_property_read_u32(np, "divider-offset",
&parameters.reg_divider_offset))
parameters.reg_divider_offset = 0;
if (of_property_read_u32(np, "divider-width",
&parameters.reg_divider_width))
parameters.reg_divider_width = 0;
if (of_property_read_u32(np, "divider-shift",
&parameters.reg_divider_shift))
parameters.reg_divider_shift = 0;
of_property_read_string(np, "clock-output-names", &clk_name);
clk = xgene_register_clk(NULL, clk_name,
of_clk_get_parent_name(np, 0), &parameters, &clk_lock);
if (IS_ERR(clk))
goto err;
pr_debug("Add %s clock\n", clk_name);
rc = of_clk_add_provider(np, of_clk_src_simple_get, clk);
if (rc != 0)
pr_err("%s: could register provider clk %pOF\n", __func__, np);
return;
err:
if (parameters.csr_reg)
iounmap(parameters.csr_reg);
if (parameters.divider_reg)
iounmap(parameters.divider_reg);
}
CLK_OF_DECLARE(xgene_socpll_clock, "apm,xgene-socpll-clock", xgene_socpllclk_init);
CLK_OF_DECLARE(xgene_pcppll_clock, "apm,xgene-pcppll-clock", xgene_pcppllclk_init);
CLK_OF_DECLARE(xgene_pmd_clock, "apm,xgene-pmd-clock", xgene_pmdclk_init);
CLK_OF_DECLARE(xgene_socpll_v2_clock, "apm,xgene-socpll-v2-clock",
xgene_socpllclk_init);
CLK_OF_DECLARE(xgene_pcppll_v2_clock, "apm,xgene-pcppll-v2-clock",
xgene_pcppllclk_init);
CLK_OF_DECLARE(xgene_dev_clock, "apm,xgene-device-clock", xgene_devclk_init);