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linux-next/arch/arm/mach-omap2/dpll44xx.c
Jon Hunter 3ff51ed828 ARM: OMAP4: Enhance support for DPLLs with 4X multiplier
On OMAP4 devices, the ABE DPLL has an internal 4X multiplier that can
be enabled or disabled in addition to the standard configurable
multiplier (M) for OMAP DPLLs. When configuring the ABE DPLL the 4X
multiplier is accounted for by checking to see whether it is enabled or
not. However, when calculating a new rate we only check to see if the
rate can be achieved with the current setting for the 4X multiplier.
Enhance the round_rate() function for such DPLLs to see if the rate
can be achieved with the 4X multiplier if it cannot be achieved without
the 4X multiplier.

This change is necessary, because when using the 32kHz clock as the
source clock for the ABE DPLL, the default DPLL frequency for the ABE
DPLL cannot be achieved without enabling the 4X multiplier.

When using the 32kHz clock as the source clock for the ABE DPLL and
attempting to lock the DPLL to 98.304MHz (default frequency), it was
found that the DPLL would fail to lock if the low-power mode for the DPLL
was not enabled. From reviewing boot-loader settings that configure the
ABE DPLL it was found that the low-power mode is enabled when using the
32kHz clock source, however, the documentation for OMAP does not state
that this is a requirement. Therefore, introduce a new function for
OMAP4 devices to see if low-power mode can be enabled when calculating a
new rate to ensure the DPLL will lock.

New variables for the last calculated 4X multiplier and low-power
setting have been added to the dpll data structure as well as variables
defining the bit mask for enabling these features via the DPLL's
control_reg. It is possible that we could eliminate these bit masks from
the dpll data structure as these bit masks are not unique to OMAP4, if
it is preferred.

The function omap3_noncore_program_dpll() has been updated to avoid
passing the calculated values for the multiplier (M) and divider (N) as
these are stored in the clk structure.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>
2012-12-15 01:35:46 -07:00

203 lines
5.3 KiB
C

/*
* OMAP4-specific DPLL control functions
*
* Copyright (C) 2011 Texas Instruments, Inc.
* Rajendra Nayak
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/bitops.h>
#include "soc.h"
#include "clock.h"
#include "clock44xx.h"
#include "cm-regbits-44xx.h"
/*
* Maximum DPLL input frequency (FINT) and output frequency (FOUT) that
* can supported when using the DPLL low-power mode. Frequencies are
* defined in OMAP4430/60 Public TRM section 3.6.3.3.2 "Enable Control,
* Status, and Low-Power Operation Mode".
*/
#define OMAP4_DPLL_LP_FINT_MAX 1000000
#define OMAP4_DPLL_LP_FOUT_MAX 100000000
/* Supported only on OMAP4 */
int omap4_dpllmx_gatectrl_read(struct clk_hw_omap *clk)
{
u32 v;
u32 mask;
if (!clk || !clk->clksel_reg || !cpu_is_omap44xx())
return -EINVAL;
mask = clk->flags & CLOCK_CLKOUTX2 ?
OMAP4430_DPLL_CLKOUTX2_GATE_CTRL_MASK :
OMAP4430_DPLL_CLKOUT_GATE_CTRL_MASK;
v = __raw_readl(clk->clksel_reg);
v &= mask;
v >>= __ffs(mask);
return v;
}
void omap4_dpllmx_allow_gatectrl(struct clk_hw_omap *clk)
{
u32 v;
u32 mask;
if (!clk || !clk->clksel_reg || !cpu_is_omap44xx())
return;
mask = clk->flags & CLOCK_CLKOUTX2 ?
OMAP4430_DPLL_CLKOUTX2_GATE_CTRL_MASK :
OMAP4430_DPLL_CLKOUT_GATE_CTRL_MASK;
v = __raw_readl(clk->clksel_reg);
/* Clear the bit to allow gatectrl */
v &= ~mask;
__raw_writel(v, clk->clksel_reg);
}
void omap4_dpllmx_deny_gatectrl(struct clk_hw_omap *clk)
{
u32 v;
u32 mask;
if (!clk || !clk->clksel_reg || !cpu_is_omap44xx())
return;
mask = clk->flags & CLOCK_CLKOUTX2 ?
OMAP4430_DPLL_CLKOUTX2_GATE_CTRL_MASK :
OMAP4430_DPLL_CLKOUT_GATE_CTRL_MASK;
v = __raw_readl(clk->clksel_reg);
/* Set the bit to deny gatectrl */
v |= mask;
__raw_writel(v, clk->clksel_reg);
}
const struct clk_hw_omap_ops clkhwops_omap4_dpllmx = {
.allow_idle = omap4_dpllmx_allow_gatectrl,
.deny_idle = omap4_dpllmx_deny_gatectrl,
};
/**
* omap4_dpll_lpmode_recalc - compute DPLL low-power setting
* @dd: pointer to the dpll data structure
*
* Calculates if low-power mode can be enabled based upon the last
* multiplier and divider values calculated. If low-power mode can be
* enabled, then the bit to enable low-power mode is stored in the
* last_rounded_lpmode variable. This implementation is based upon the
* criteria for enabling low-power mode as described in the OMAP4430/60
* Public TRM section 3.6.3.3.2 "Enable Control, Status, and Low-Power
* Operation Mode".
*/
static void omap4_dpll_lpmode_recalc(struct dpll_data *dd)
{
long fint, fout;
fint = __clk_get_rate(dd->clk_ref) / (dd->last_rounded_n + 1);
fout = fint * dd->last_rounded_m;
if ((fint < OMAP4_DPLL_LP_FINT_MAX) && (fout < OMAP4_DPLL_LP_FOUT_MAX))
dd->last_rounded_lpmode = 1;
else
dd->last_rounded_lpmode = 0;
}
/**
* omap4_dpll_regm4xen_recalc - compute DPLL rate, considering REGM4XEN bit
* @clk: struct clk * of the DPLL to compute the rate for
*
* Compute the output rate for the OMAP4 DPLL represented by @clk.
* Takes the REGM4XEN bit into consideration, which is needed for the
* OMAP4 ABE DPLL. Returns the DPLL's output rate (before M-dividers)
* upon success, or 0 upon error.
*/
unsigned long omap4_dpll_regm4xen_recalc(struct clk_hw *hw,
unsigned long parent_rate)
{
struct clk_hw_omap *clk = to_clk_hw_omap(hw);
u32 v;
unsigned long rate;
struct dpll_data *dd;
if (!clk || !clk->dpll_data)
return 0;
dd = clk->dpll_data;
rate = omap2_get_dpll_rate(clk);
/* regm4xen adds a multiplier of 4 to DPLL calculations */
v = __raw_readl(dd->control_reg);
if (v & OMAP4430_DPLL_REGM4XEN_MASK)
rate *= OMAP4430_REGM4XEN_MULT;
return rate;
}
/**
* omap4_dpll_regm4xen_round_rate - round DPLL rate, considering REGM4XEN bit
* @clk: struct clk * of the DPLL to round a rate for
* @target_rate: the desired rate of the DPLL
*
* Compute the rate that would be programmed into the DPLL hardware
* for @clk if set_rate() were to be provided with the rate
* @target_rate. Takes the REGM4XEN bit into consideration, which is
* needed for the OMAP4 ABE DPLL. Returns the rounded rate (before
* M-dividers) upon success, -EINVAL if @clk is null or not a DPLL, or
* ~0 if an error occurred in omap2_dpll_round_rate().
*/
long omap4_dpll_regm4xen_round_rate(struct clk_hw *hw,
unsigned long target_rate,
unsigned long *parent_rate)
{
struct clk_hw_omap *clk = to_clk_hw_omap(hw);
struct dpll_data *dd;
long r;
if (!clk || !clk->dpll_data)
return -EINVAL;
dd = clk->dpll_data;
dd->last_rounded_m4xen = 0;
/*
* First try to compute the DPLL configuration for
* target rate without using the 4X multiplier.
*/
r = omap2_dpll_round_rate(hw, target_rate, NULL);
if (r != ~0)
goto out;
/*
* If we did not find a valid DPLL configuration, try again, but
* this time see if using the 4X multiplier can help. Enabling the
* 4X multiplier is equivalent to dividing the target rate by 4.
*/
r = omap2_dpll_round_rate(hw, target_rate / OMAP4430_REGM4XEN_MULT,
NULL);
if (r == ~0)
return r;
dd->last_rounded_rate *= OMAP4430_REGM4XEN_MULT;
dd->last_rounded_m4xen = 1;
out:
omap4_dpll_lpmode_recalc(dd);
return dd->last_rounded_rate;
}