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hw/misc/bcm2835_cprman: implement clock mux behaviour

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A clock mux can be configured to select one of its 10 sources through
the CM_CTL register. It also embeds yet another clock divider, composed
of an integer part and a fractional part. The number of bits of each
part is mux dependent.

Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Luc Michel <luc@lmichel.fr>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Luc Michel 2020-10-10 15:57:55 +02:00 committed by Peter Maydell
parent 7281362484
commit fc9840850b
1 changed files with 52 additions and 1 deletions
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53
hw/misc/bcm2835_cprman.c
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@ -231,15 +231,66 @@ static const TypeInfo cprman_pll_channel_info = {
/* clock mux */
static bool clock_mux_is_enabled(CprmanClockMuxState *mux)
{
return FIELD_EX32(*mux->reg_ctl, CM_CLOCKx_CTL, ENABLE);
}
static void clock_mux_update(CprmanClockMuxState *mux)
{
clock_update(mux->out, 0);
uint64_t freq;
uint32_t div, src = FIELD_EX32(*mux->reg_ctl, CM_CLOCKx_CTL, SRC);
bool enabled = clock_mux_is_enabled(mux);
*mux->reg_ctl = FIELD_DP32(*mux->reg_ctl, CM_CLOCKx_CTL, BUSY, enabled);
if (!enabled) {
clock_update(mux->out, 0);
return;
}
freq = clock_get_hz(mux->srcs[src]);
if (mux->int_bits == 0 && mux->frac_bits == 0) {
clock_update_hz(mux->out, freq);
return;
}
/*
* The divider has an integer and a fractional part. The size of each part
* varies with the muxes (int_bits and frac_bits). Both parts are
* concatenated, with the integer part always starting at bit 12.
*
* 31 12 11 0
* ------------------------------
* CM_DIV | | int | frac | |
* ------------------------------
* <-----> <------>
* int_bits frac_bits
*/
div = extract32(*mux->reg_div,
R_CM_CLOCKx_DIV_FRAC_LENGTH - mux->frac_bits,
mux->int_bits + mux->frac_bits);
if (!div) {
clock_update(mux->out, 0);
return;
}
freq = muldiv64(freq, 1 << mux->frac_bits, div);
clock_update_hz(mux->out, freq);
}
static void clock_mux_src_update(void *opaque)
{
CprmanClockMuxState **backref = opaque;
CprmanClockMuxState *s = *backref;
CprmanClockMuxSource src = backref - s->backref;
if (FIELD_EX32(*s->reg_ctl, CM_CLOCKx_CTL, SRC) != src) {
return;
}
clock_mux_update(s);
}