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linux/arch/arm/mach-omap2/sram34xx.S
Paul Walmsley 4519c2bf43 OMAP3 clock: only unlock SDRC DLL if SDRC clk < 83MHz 
According to the 34xx TRM Rev. K section 11.2.4.4.11.1 "Purpose of the
DLL/CDL Module," the SDRC delay-locked-loop can be locked at any SDRC
clock frequency from 83MHz to 166MHz.  CDP code unconditionally
unlocked the DLL whenever shifting to a lower SDRC speed, but this
seems unnecessary and error-prone, as the DLL is no longer able to
compensate for process, voltage, and temperature variations.  Instead,
only unlock the DLL when the SDRC clock rate would be less than 83MHz.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
2009-05-12 17:27:10 -06:00

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/*
* linux/arch/arm/mach-omap3/sram.S
*
* Omap3 specific functions that need to be run in internal SRAM
*
* (C) Copyright 2007
* Texas Instruments Inc.
* Rajendra Nayak <rnayak@ti.com>
*
* (C) Copyright 2004
* Texas Instruments, <www.ti.com>
* Richard Woodruff <r-woodruff2@ti.com>
*
* 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
*/
#include <linux/linkage.h>
#include <asm/assembler.h>
#include <mach/hardware.h>
#include <mach/io.h>
#include "sdrc.h"
#include "cm.h"
.text
/*
* Change frequency of core dpll
* r0 = sdrc_rfr_ctrl r1 = sdrc_actim_ctrla r2 = sdrc_actim_ctrlb r3 = M2
* r4 = Unlock SDRC DLL? (1 = yes, 0 = no) -- only unlock DLL for
* SDRC rates < 83MHz
*/
ENTRY(omap3_sram_configure_core_dpll)
stmfd sp!, {r1-r12, lr} @ store regs to stack
ldr r4, [sp, #52] @ pull extra args off the stack
dsb @ flush buffered writes to interconnect
cmp r3, #0x2
blne configure_sdrc
cmp r4, #0x1
bleq unlock_dll
blne lock_dll
bl sdram_in_selfrefresh @ put the SDRAM in self refresh
bl configure_core_dpll
bl enable_sdrc
cmp r4, #0x1
bleq wait_dll_unlock
blne wait_dll_lock
cmp r3, #0x1
blne configure_sdrc
isb @ prevent speculative exec past here
mov r0, #0 @ return value
ldmfd sp!, {r1-r12, pc} @ restore regs and return
unlock_dll:
ldr r11, omap3_sdrc_dlla_ctrl
ldr r12, [r11]
orr r12, r12, #0x4
str r12, [r11] @ (no OCP barrier needed)
bx lr
lock_dll:
ldr r11, omap3_sdrc_dlla_ctrl
ldr r12, [r11]
bic r12, r12, #0x4
str r12, [r11] @ (no OCP barrier needed)
bx lr
sdram_in_selfrefresh:
ldr r11, omap3_sdrc_power @ read the SDRC_POWER register
ldr r12, [r11] @ read the contents of SDRC_POWER
mov r9, r12 @ keep a copy of SDRC_POWER bits
orr r12, r12, #0x40 @ enable self refresh on idle req
bic r12, r12, #0x4 @ clear PWDENA
str r12, [r11] @ write back to SDRC_POWER register
ldr r12, [r11] @ posted-write barrier for SDRC
ldr r11, omap3_cm_iclken1_core @ read the CM_ICLKEN1_CORE reg
ldr r12, [r11]
bic r12, r12, #0x2 @ disable iclk bit for SDRC
str r12, [r11]
wait_sdrc_idle:
ldr r11, omap3_cm_idlest1_core
ldr r12, [r11]
and r12, r12, #0x2 @ check for SDRC idle
cmp r12, #2
bne wait_sdrc_idle
bx lr
configure_core_dpll:
ldr r11, omap3_cm_clksel1_pll
ldr r12, [r11]
ldr r10, core_m2_mask_val @ modify m2 for core dpll
and r12, r12, r10
orr r12, r12, r3, lsl #0x1B @ r3 contains the M2 val
str r12, [r11]
ldr r12, [r11] @ posted-write barrier for CM
mov r12, #0x800 @ wait for the clock to stabilise
cmp r3, #2
bne wait_clk_stable
bx lr
wait_clk_stable:
subs r12, r12, #1
bne wait_clk_stable
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
bx lr
enable_sdrc:
ldr r11, omap3_cm_iclken1_core
ldr r12, [r11]
orr r12, r12, #0x2 @ enable iclk bit for SDRC
str r12, [r11]
wait_sdrc_idle1:
ldr r11, omap3_cm_idlest1_core
ldr r12, [r11]
and r12, r12, #0x2
cmp r12, #0
bne wait_sdrc_idle1
restore_sdrc_power_val:
ldr r11, omap3_sdrc_power
str r9, [r11] @ restore SDRC_POWER, no barrier needed
bx lr
wait_dll_lock:
ldr r11, omap3_sdrc_dlla_status
ldr r12, [r11]
and r12, r12, #0x4
cmp r12, #0x4
bne wait_dll_lock
bx lr
wait_dll_unlock:
ldr r11, omap3_sdrc_dlla_status
ldr r12, [r11]
and r12, r12, #0x4
cmp r12, #0x0
bne wait_dll_unlock
bx lr
configure_sdrc:
ldr r11, omap3_sdrc_rfr_ctrl
str r0, [r11]
ldr r11, omap3_sdrc_actim_ctrla
str r1, [r11]
ldr r11, omap3_sdrc_actim_ctrlb
str r2, [r11]
ldr r2, [r11] @ posted-write barrier for SDRC
bx lr
omap3_sdrc_power:
.word OMAP34XX_SDRC_REGADDR(SDRC_POWER)
omap3_cm_clksel1_pll:
.word OMAP34XX_CM_REGADDR(PLL_MOD, CM_CLKSEL1)
omap3_cm_idlest1_core:
.word OMAP34XX_CM_REGADDR(CORE_MOD, CM_IDLEST)
omap3_cm_iclken1_core:
.word OMAP34XX_CM_REGADDR(CORE_MOD, CM_ICLKEN1)
omap3_sdrc_rfr_ctrl:
.word OMAP34XX_SDRC_REGADDR(SDRC_RFR_CTRL_0)
omap3_sdrc_actim_ctrla:
.word OMAP34XX_SDRC_REGADDR(SDRC_ACTIM_CTRL_A_0)
omap3_sdrc_actim_ctrlb:
.word OMAP34XX_SDRC_REGADDR(SDRC_ACTIM_CTRL_B_0)
omap3_sdrc_dlla_status:
.word OMAP34XX_SDRC_REGADDR(SDRC_DLLA_STATUS)
omap3_sdrc_dlla_ctrl:
.word OMAP34XX_SDRC_REGADDR(SDRC_DLLA_CTRL)
core_m2_mask_val:
.word 0x07FFFFFF
ENTRY(omap3_sram_configure_core_dpll_sz)
.word . - omap3_sram_configure_core_dpll
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