[PATCH 10/14] hw/misc/bcm2835_cprman: implement clock mux behaviour

[Luc Michel <luc@lmichel.fr>]

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 fractionnal part. The number of bits of each
part is mux dependant.

Signed-off-by: Luc Michel <luc@lmichel.fr>
---
 hw/misc/bcm2835_cprman.c | 43 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/hw/misc/bcm2835_cprman.c b/hw/misc/bcm2835_cprman.c
index 8df2db0fd9..75bc11939b 100644
--- a/hw/misc/bcm2835_cprman.c
+++ b/hw/misc/bcm2835_cprman.c
@@ -229,19 +229,60 @@ static const TypeInfo cprman_pll_channel_info = {
 };
 
 
 /* clock mux */
 
+static bool clock_mux_is_enabled(CprmanClockMuxState *mux)
+{
+    return FIELD_EX32(*mux->reg_cm, CM_CLOCKx_CTL, ENABLE);
+}
+
 static void clock_mux_update(CprmanClockMuxState *mux)
 {
-    clock_update(mux->out, 0);
+    uint64_t freq, div;
+    uint32_t src = FIELD_EX32(*mux->reg_cm, CM_CLOCKx_CTL, SRC);
+    bool enabled = clock_mux_is_enabled(mux);
+
+    *mux->reg_cm = FIELD_DP32(*mux->reg_cm, 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.
+     */
+    div = mux->reg_cm[1] >> (R_CM_CLOCKx_DIV_FRAC_LENGTH - mux->frac_bits);
+    div &= (1 << (mux->int_bits + mux->frac_bits)) - 1;
+
+    freq = (freq << 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;
+    uint32_t current_src;
+
+    current_src = FIELD_EX32(*s->reg_cm, CM_CLOCKx_CTL, SRC);
+
+    if (current_src != src) {
+        return;
+    }
 
     clock_mux_update(s);
 }
 
 static void clock_mux_init(Object *obj)
-- 
2.28.0