mirror of
https://github.com/isometimes/rpi4-osdev
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98 lines
2.6 KiB
C
98 lines
2.6 KiB
C
#include "../include/io.h"
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#include "../include/mb.h"
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// The buffer must be 16-byte aligned as only the upper 28 bits of the address can be passed via the mailbox
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volatile unsigned int __attribute__((aligned(16))) mbox[36];
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enum {
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VIDEOCORE_MBOX = (PERIPHERAL_BASE + 0x0000B880),
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MBOX_READ = (VIDEOCORE_MBOX + 0x0),
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MBOX_POLL = (VIDEOCORE_MBOX + 0x10),
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MBOX_SENDER = (VIDEOCORE_MBOX + 0x14),
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MBOX_STATUS = (VIDEOCORE_MBOX + 0x18),
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MBOX_CONFIG = (VIDEOCORE_MBOX + 0x1C),
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MBOX_WRITE = (VIDEOCORE_MBOX + 0x20),
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MBOX_RESPONSE = 0x80000000,
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MBOX_FULL = 0x80000000,
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MBOX_EMPTY = 0x40000000
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};
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unsigned int mbox_call(unsigned char ch)
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{
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// 28-bit address (MSB) and 4-bit value (LSB)
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unsigned int r = ((unsigned int)((long) &mbox) &~ 0xF) | (ch & 0xF);
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// Wait until we can write
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while (mmio_read(MBOX_STATUS) & MBOX_FULL);
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// Write the address of our buffer to the mailbox with the channel appended
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mmio_write(MBOX_WRITE, r);
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while (1) {
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// Is there a reply?
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while (mmio_read(MBOX_STATUS) & MBOX_EMPTY);
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// Is it a reply to our message?
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if (r == mmio_read(MBOX_READ)) return mbox[1]==MBOX_RESPONSE; // Is it successful?
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}
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return 0;
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}
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int get_max_clock()
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{
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mbox[0] = 8*4; // Length of message in bytes
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mbox[1] = MBOX_REQUEST;
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mbox[2] = MBOX_TAG_GETCLKMAXM; // Tag identifier
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mbox[3] = 8; // Value size in bytes
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mbox[4] = 0; // Value size in bytes
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mbox[5] = 0x3; // Value
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mbox[6] = 0; // Rate
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mbox[7] = MBOX_TAG_LAST;
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if (mbox_call(MBOX_CH_PROP)) {
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if (mbox[5] == 0x3) {
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return mbox[6];
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}
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}
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return 0;
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}
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int get_clock_rate()
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{
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mbox[0] = 8*4; // Length of message in bytes
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mbox[1] = MBOX_REQUEST;
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mbox[2] = MBOX_TAG_GETCLKRATE; // Tag identifier
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mbox[3] = 8; // Value size in bytes
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mbox[4] = 0; // Value size in bytes
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mbox[5] = 0x3; // Value
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mbox[6] = 0; // Rate
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mbox[7] = MBOX_TAG_LAST;
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if (mbox_call(MBOX_CH_PROP)) {
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if (mbox[5] == 0x3) {
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return mbox[6];
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}
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}
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return 0;
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}
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int set_clock_rate(unsigned int rate)
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{
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mbox[0] = 9*4; // Length of message in bytes
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mbox[1] = MBOX_REQUEST;
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mbox[2] = MBOX_TAG_SETCLKRATE; // Tag identifier
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mbox[3] = 12; // Value size in bytes
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mbox[4] = 0; // Value size in bytes
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mbox[5] = 0x3; // Value
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mbox[6] = rate; // Rate
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mbox[7] = 0; // Rate
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mbox[8] = MBOX_TAG_LAST;
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if (mbox_call(MBOX_CH_PROP)) {
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if (mbox[5] == 0x3 && mbox[6] == rate) {
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return 1;
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}
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}
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return 0;
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}
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