48 lines
1.0 KiB
C
48 lines
1.0 KiB
C
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/*
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* Access system mailboxes
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*/
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#include "rpi_mailbox.h"
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/* Mailbox memory addresses */
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static volatile unsigned int *MAILBOX0READ = (unsigned int *) (0x2000b880);
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static volatile unsigned int *MAILBOX0STATUS = (unsigned int *) (0x2000b898);
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static volatile unsigned int *MAILBOX0WRITE = (unsigned int *) (0x2000b8a0);
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/* Bit 31 set in status register if the write mailbox is full */
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#define MAILBOX_FULL 0x80000000
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/* Bit 30 set in status register if the read mailbox is empty */
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#define MAILBOX_EMPTY 0x40000000
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unsigned int rpi_readmailbox(unsigned int channel)
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{
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unsigned int val;
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if (channel > 15)
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return 0xFFFFFFFF;
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/* Wait for mailbox to be full */
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while (*MAILBOX0STATUS & MAILBOX_EMPTY);
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val = *MAILBOX0READ;
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if ((val & 15) == channel)
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return (val & 0xFFFFFFF0);
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else
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return 0xFFFFFFFF;
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}
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void rpi_writemailbox(unsigned int channel, unsigned int data)
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{
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if (channel > 15)
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return;
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if (data & 0x000F)
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return;
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/* Wait for mailbox to be not full */
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while (*MAILBOX0STATUS & MAILBOX_FULL);
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*MAILBOX0WRITE = (data | channel);
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}
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