[PATCH 1/3] imx6: clock: improve calculations to get the PLL video rate

[Michael Nazzareno Trimarchi]

On Sat, Feb 25, 2023 at 9:38 AM Dario Binacchi
<dario.binacchi at amarulasolutions.com> wrote:
>
> During some tests to check the pixel clock rate in the transition from
> U-Boot to the Linux kernel, I noticed that with the same configuration
> of the registers the debug messages reported different rates.
>
> The same Linux kernel calculations are now used to get the PLL video
> rate.
>
> Signed-off-by: Dario Binacchi <dario.binacchi at amarulasolutions.com>
> ---
>
>  arch/arm/mach-imx/mx6/clock.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/mach-imx/mx6/clock.c b/arch/arm/mach-imx/mx6/clock.c
> index cb9d629be408..17d8dcd5c841 100644
> --- a/arch/arm/mach-imx/mx6/clock.c
> +++ b/arch/arm/mach-imx/mx6/clock.c
> @@ -213,6 +213,7 @@ int enable_spi_clk(unsigned char enable, unsigned spi_num)
>  static u32 decode_pll(enum pll_clocks pll, u32 infreq)
>  {
>         u32 div, test_div, pll_num, pll_denom;
> +       u64 temp64;
>
>         switch (pll) {
>         case PLL_SYS:
> @@ -272,7 +273,10 @@ static u32 decode_pll(enum pll_clocks pll, u32 infreq)
>                 }
>                 test_div = 1 << (2 - test_div);
>
> -               return infreq * (div + pll_num / pll_denom) / test_div;
> +               temp64 = (u64)infreq;
> +               temp64 *= pll_num;
> +               do_div(temp64, pll_denom);
> +               return infreq * div + (unsigned long)temp64;
>         default:
>                 return 0;

Reviewed-by: Michael Trimarchi <michael at amarulasolutions.com>
>         }
> --
> 2.32.0
>
>


-- 
Michael Nazzareno Trimarchi
Co-Founder & Chief Executive Officer
M. +39 347 913 2170
michael at amarulasolutions.com
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