[PATCH 06/14] hw/misc/bcm2835_cprman: implement PLLs behaviour

[Luc Michel]

The cprman PLLs generate a clock based on a prescaler, a multiplier and
a divider. The prescaler doubles the parent (xosc) frequency, then the
multiplier/divider are applied. The multiplier has an integer and a
fractionnal part.

This commit also implements the cprman CM_LOCK register. This register
reports which PLL is currently locked. We consider a PLL has being
locked as soon as it is enabled (on real hardware, there is a delay
after turning a PLL on, for it to stabilise).

Signed-off-by: Luc Michel <luc@lmichel.fr>
---
 include/hw/misc/bcm2835_cprman_internals.h |  8 +++
 hw/misc/bcm2835_cprman.c                   | 64 +++++++++++++++++++++-
 2 files changed, 71 insertions(+), 1 deletion(-)

diff --git a/include/hw/misc/bcm2835_cprman_internals.h 
b/include/hw/misc/bcm2835_cprman_internals.h
index 5cfa849492..22a2500ab0 100644
--- a/include/hw/misc/bcm2835_cprman_internals.h
+++ b/include/hw/misc/bcm2835_cprman_internals.h
@@ -98,10 +98,18 @@ REG32(A2W_PLLA_FRAC, 0x1200)
 REG32(A2W_PLLC_FRAC, 0x1220)
 REG32(A2W_PLLD_FRAC, 0x1240)
 REG32(A2W_PLLH_FRAC, 0x1260)
 REG32(A2W_PLLB_FRAC, 0x12e0)
 
+/* misc registers */
+REG32(CM_LOCK, 0x114)
+    FIELD(CM_LOCK, FLOCKH, 12, 1)
+    FIELD(CM_LOCK, FLOCKD, 11, 1)
+    FIELD(CM_LOCK, FLOCKC, 10, 1)
+    FIELD(CM_LOCK, FLOCKB, 9, 1)
+    FIELD(CM_LOCK, FLOCKA, 8, 1)
+
 /*
  * This field is common to all registers. Each register write value must match
  * the CPRMAN_PASSWORD magic value in its 8 MSB.
  */
 FIELD(CPRMAN, PASSWORD, 24, 8)
diff --git a/hw/misc/bcm2835_cprman.c b/hw/misc/bcm2835_cprman.c
index ad71d30a86..ba82522eb1 100644
--- a/hw/misc/bcm2835_cprman.c
+++ b/hw/misc/bcm2835_cprman.c
@@ -48,13 +48,51 @@
 #include "hw/misc/bcm2835_cprman_internals.h"
 #include "trace.h"
 
 /* PLL */
 
+static bool pll_is_locked(const CprmanPLLState *pll)
+{
+    return !FIELD_EX32(*pll->reg_a2w_ctrl, A2W_PLLx_CTRL, PWRDN)
+        && !FIELD_EX32(*pll->reg_cm, CM_PLLx, ANARST);
+}
+
 static void pll_update(CprmanPLLState *pll)
 {
-    clock_update(pll->out, 0);
+    uint64_t freq, ndiv, fdiv, pdiv;
+
+    if (!pll_is_locked(pll)) {
+        clock_update(pll->out, 0);
+        return;
+    }
+
+    pdiv = FIELD_EX32(*pll->reg_a2w_ctrl, A2W_PLLx_CTRL, PDIV);
+
+    if (!pdiv) {
+        clock_update(pll->out, 0);
+        return;
+    }
+
+    ndiv = FIELD_EX32(*pll->reg_a2w_ctrl, A2W_PLLx_CTRL, NDIV);
+    fdiv = FIELD_EX32(*pll->reg_a2w_frac, A2W_PLLx_FRAC, FRAC);
+
+    if (pll->reg_a2w_ana[1] & pll->prediv_mask) {
+        /* The prescaler doubles the parent frequency */
+        ndiv *= 2;
+        fdiv *= 2;
+    }
+
+    /*
+     * We have a multiplier with an integer part (ndiv) and a fractional part
+     * (fdiv), and a divider (pdiv).
+     */
+    freq = clock_get_hz(pll->xosc_in) *
+        ((ndiv << R_A2W_PLLx_FRAC_FRAC_LENGTH) + fdiv);
+    freq /= pdiv;
+    freq >>= R_A2W_PLLx_FRAC_FRAC_LENGTH;
+
+    clock_update_hz(pll->out, freq);
 }
 
 static void pll_xosc_update(void *opaque)
 {
     pll_update(CPRMAN_PLL(opaque));
@@ -94,18 +132,42 @@ static const TypeInfo cprman_pll_info = {
 };
 
 
 /* CPRMAN "top level" model */
 
+static uint32_t get_cm_lock(const BCM2835CprmanState *s)
+{
+    static const int CM_LOCK_MAPPING[] = {
+        [CPRMAN_PLLA] = R_CM_LOCK_FLOCKA_SHIFT,
+        [CPRMAN_PLLC] = R_CM_LOCK_FLOCKC_SHIFT,
+        [CPRMAN_PLLD] = R_CM_LOCK_FLOCKD_SHIFT,
+        [CPRMAN_PLLH] = R_CM_LOCK_FLOCKH_SHIFT,
+        [CPRMAN_PLLB] = R_CM_LOCK_FLOCKB_SHIFT,
+    };
+
+    uint32_t r = 0;
+    size_t i;
+
+    for (i = 0; i < CPRMAN_NUM_PLL; i++) {
+        r |= pll_is_locked(&s->plls[i]) << CM_LOCK_MAPPING[i];
+    }
+
+    return r;
+}
+
 static uint64_t cprman_read(void *opaque, hwaddr offset,
                                     unsigned size)
 {
     BCM2835CprmanState *s = CPRMAN(opaque);
     uint64_t r = 0;
     size_t idx = offset / sizeof(uint32_t);
 
     switch (idx) {
+    case R_CM_LOCK:
+        r = get_cm_lock(s);
+        break;
+
     default:
         r = s->regs[idx];
     }
 
     trace_bcm2835_cprman_read(offset, r);
-- 
2.28.0