diff options
Diffstat (limited to 'os/mpc/pit.c')
| -rw-r--r-- | os/mpc/pit.c | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/os/mpc/pit.c b/os/mpc/pit.c new file mode 100644 index 00000000..bfc8bc8d --- /dev/null +++ b/os/mpc/pit.c @@ -0,0 +1,68 @@ +/* + * programmable interrupt timer + */ + +#include "u.h" +#include "../port/lib.h" +#include "mem.h" +#include "dat.h" +#include "fns.h" +#include "io.h" +#include "ureg.h" + +enum { + /* piscr */ + PTE = 1<<0, + PITF = 1<<1, + PIE = 1<<2, + PS = 1<<7, +}; + +static void +pitinterrupt(Ureg*, void*) +{ + IMM *io; + + io = m->iomem; + if(io->piscr & PS){ + io->piscr |= PS; /* clear by writing 1 */ + /* do whatever is required */ + } +} + +static void +pitreset(void) +{ + IMM *io; + + io = ioplock(); + io->piscrk = KEEP_ALIVE_KEY; + io->piscr = (PITlevel<<8) | PS | PITF; + if(0) + io->piscrk = ~KEEP_ALIVE_KEY; + /* piscrk is left unlocked for interrupt routine */ + iopunlock(); + intrenable(PITlevel, pitinterrupt, nil, BUSUNKNOWN, "pit"); +} + +static ulong +pitload(ulong usec) +{ + IMM *io; + ulong v; + + v = ((usec*m->oscclk)/512); + if(v == 0 || v >= (1<<16)) + return 0; /* can't do */ + io = ioplock(); + io->pitck = KEEP_ALIVE_KEY; + io->pitc = (v-1)<<16; + io->pitck = ~KEEP_ALIVE_KEY; + io->piscrk = KEEP_ALIVE_KEY; + io->piscr = (PITlevel<<8) | PS | PIE | PITF | PTE; + if(0) + io->piscrk = ~KEEP_ALIVE_KEY; + /* piscrk is left unlocked for interrupt routine */ + iopunlock(); + return (v*512)/m->oscclk; +} |