Hi Biju,
On Wed, Oct 9, 2024 at 4:03 PM Biju Das <biju.das.jz@xxxxxxxxxxxxxx> wrote:
> While computing foutpostdiv_rate, the value of params->pl5_fracin
> is discarded, which results in the wrong refresh rate. Fix the formula
> for computing foutpostdiv_rate.
>
> Fixes: 1561380ee72f ("clk: renesas: rzg2l: Add FOUTPOSTDIV clk support")
> Signed-off-by: Hien Huynh <hien.huynh.px@xxxxxxxxxxx>
> Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
Thanks for your patch!
> --- a/drivers/clk/renesas/rzg2l-cpg.c
> +++ b/drivers/clk/renesas/rzg2l-cpg.c
> @@ -548,7 +548,7 @@ static unsigned long
> rzg2l_cpg_get_foutpostdiv_rate(struct rzg2l_pll5_param *params,
> unsigned long rate)
> {
> - unsigned long foutpostdiv_rate;
> + unsigned long foutpostdiv_rate, foutvco_rate;
>
> params->pl5_intin = rate / MEGA;
> params->pl5_fracin = div_u64(((u64)rate % MEGA) << 24, MEGA);
> @@ -557,10 +557,12 @@ rzg2l_cpg_get_foutpostdiv_rate(struct rzg2l_pll5_param *params,
> params->pl5_postdiv2 = 1;
> params->pl5_spread = 0x16;
>
> - foutpostdiv_rate =
> - EXTAL_FREQ_IN_MEGA_HZ * MEGA / params->pl5_refdiv *
> - ((((params->pl5_intin << 24) + params->pl5_fracin)) >> 24) /
> - (params->pl5_postdiv1 * params->pl5_postdiv2);
> + foutvco_rate = EXTAL_FREQ_IN_MEGA_HZ * MEGA / params->pl5_refdiv;
> + foutvco_rate = mul_u64_u32_shr(foutvco_rate,
> + (params->pl5_intin << 24) + params->pl5_fracin,
> + 24);
The first parameter is not u64, but unsigned long, and its value always
fits in u32, so "mul_u32_u32(..., ...) >> 24" should do?
However, if you care about precision, the division by params->pl5_refdiv
should be done after all multiplication, too.
> + foutpostdiv_rate = DIV_ROUND_CLOSEST_ULL(foutvco_rate,
> + params->pl5_postdiv1 * params->pl5_postdiv2);
>
> return foutpostdiv_rate;
> }
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
