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

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

On 9/25/20 12:17 PM, Luc Michel wrote:
> 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

Typo "fractional".

> part is mux dependant.

Typo "dependent"?

> 
> 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)
>