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/*
* framebuffer.s
*
* Copyright © 2018 Thomas White <taw@bitwiz.org.uk>
*
* 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 3 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, see <http://www.gnu.org/licenses/>.
*
*/
.include "ports.h"
.global framebuffer_init
framebuffer_init:
STMDB R13!, {R14}
ADR R1, framebuffer_info
ADD R1, R1, #0x40000000
MOV R0, #1
BL send_mailbox
@ BL read_mailbox
CMP R1, #0
LDMNEIA R13!, {PC} @ Fail
LDMIA R13!, {PC}
/* -> R0 = mailbox number
* R1 = value to write */
send_mailbox:
STMDB R13!, {R2, R8, R14}
LDR R8, =(PERIPHERAL_BASE+OFFS_MAILBOX)
/* Wait for empty mailbox */
1:
LDR R2, [R8, #18]
TST R2, #1<<31
BNE 1b
AND R2, R0, #0xf
ORR R2, R2, R1
STR R2, [R8, #20]
LDMIA R13!, {R2, R8, PC}
/* -> R0 = mailbox number
* <- R1 = value read */
read_mailbox:
STMDB R13!, {R2, R8, R14}
LDR R8, =(PERIPHERAL_BASE+OFFS_MAILBOX)
/* Wait for non-empty mailbox */
1:
LDR R2, [R8, #18]
TST R2, #1<<30
BNE 1b
LDR R2, [R8, #0]
AND R1, R2, #0xf
CMP R1, R0
BNE 1b @ Wrong mailbox
BIC R1, R2, #0xf
LDMIA R13!, {R2, R8, PC}
.align 4
framebuffer_info:
.int 1024
.int 768
.int 1024
.int 768
.int 0
.int 16
.int 0
.int 0
.int 0
.int 0
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