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self-refresh.S
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self-refresh.S
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/*
* Copyright (C) 2014-2015 Altera 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.
*
* You should have received a copy of the GNU General Public License along with
* this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <linux/linkage.h>
#include <asm/assembler.h>
#define MAX_LOOP_COUNT 1000
/* Register offset */
#define SDR_CTRLGRP_LOWPWREQ_ADDR 0x54
#define SDR_CTRLGRP_LOWPWRACK_ADDR 0x58
/* Bitfield positions */
#define SELFRSHREQ_POS 3
#define SELFRSHREQ_MASK 0x8
#define SELFRFSHACK_POS 1
#define SELFRFSHACK_MASK 0x2
/*
* This code assumes that when the bootloader configured
* the sdram controller for the DDR on the board it
* configured the following fields depending on the DDR
* vendor/configuration:
*
* sdr.ctrlcfg.lowpwreq.selfrfshmask
* sdr.ctrlcfg.lowpwrtiming.clkdisablecycles
* sdr.ctrlcfg.dramtiming4.selfrfshexit
*/
.arch armv7-a
.text
.align 3
/*
* socfpga_sdram_self_refresh
*
* r0 : sdr_ctl_base_addr
* r1 : temp storage of return value
* r2 : temp storage of register values
* r3 : loop counter
*
* return value: lower 16 bits: loop count going into self refresh
* upper 16 bits: loop count exiting self refresh
*/
ENTRY(socfpga_sdram_self_refresh)
/* Enable dynamic clock gating in the Power Control Register. */
mrc p15, 0, r2, c15, c0, 0
orr r2, r2, #1
mcr p15, 0, r2, c15, c0, 0
/* Enable self refresh: set sdr.ctrlgrp.lowpwreq.selfrshreq = 1 */
ldr r2, [r0, #SDR_CTRLGRP_LOWPWREQ_ADDR]
orr r2, r2, #SELFRSHREQ_MASK
str r2, [r0, #SDR_CTRLGRP_LOWPWREQ_ADDR]
/* Poll until sdr.ctrlgrp.lowpwrack.selfrfshack == 1 or hit max loops */
mov r3, #0
while_ack_0:
ldr r2, [r0, #SDR_CTRLGRP_LOWPWRACK_ADDR]
and r2, r2, #SELFRFSHACK_MASK
cmp r2, #SELFRFSHACK_MASK
beq ack_1
add r3, #1
cmp r3, #MAX_LOOP_COUNT
bne while_ack_0
ack_1:
mov r1, r3
/*
* Execute an ISB instruction to ensure that all of the
* CP15 register changes have been committed.
*/
isb
/*
* Execute a barrier instruction to ensure that all cache,
* TLB and branch predictor maintenance operations issued
* by any CPU in the cluster have completed.
*/
dsb
dmb
wfi
/* Disable self-refresh: set sdr.ctrlgrp.lowpwreq.selfrshreq = 0 */
ldr r2, [r0, #SDR_CTRLGRP_LOWPWREQ_ADDR]
bic r2, r2, #SELFRSHREQ_MASK
str r2, [r0, #SDR_CTRLGRP_LOWPWREQ_ADDR]
/* Poll until sdr.ctrlgrp.lowpwrack.selfrfshack == 0 or hit max loops */
mov r3, #0
while_ack_1:
ldr r2, [r0, #SDR_CTRLGRP_LOWPWRACK_ADDR]
and r2, r2, #SELFRFSHACK_MASK
cmp r2, #SELFRFSHACK_MASK
bne ack_0
add r3, #1
cmp r3, #MAX_LOOP_COUNT
bne while_ack_1
ack_0:
/*
* Prepare return value:
* Shift loop count for exiting self refresh into upper 16 bits.
* Leave loop count for requesting self refresh in lower 16 bits.
*/
mov r3, r3, lsl #16
add r1, r1, r3
/* Disable dynamic clock gating in the Power Control Register. */
mrc p15, 0, r2, c15, c0, 0
bic r2, r2, #1
mcr p15, 0, r2, c15, c0, 0
mov r0, r1 @ return value
bx lr @ return
ENDPROC(socfpga_sdram_self_refresh)
ENTRY(socfpga_sdram_self_refresh_sz)
.word . - socfpga_sdram_self_refresh