Re: [PATCH 06/19] clk: at91: sam9x60-pll: check fcore against ranges

Alexandre Belloni
2020-07-17T09:25:38Z

On 15/07/2020 14:24:14+0300, Claudiu Beznea wrote:
> According to datasheet the range of 600-1200MHz is for the the

the is repeated here

> frequency generated by the fractional part of the PLL (namely
> Fcorepllck according to datasheet). With this in mind the output
> range of the PLL itself (fractional + div), taking into account
> that the diverder is 8 bits wide, is 600/256-1200Hz=2.3-1200MHz.
>

divider

> Fixes: a436c2a447e59 ("clk: at91: add sam9x60 PLL driver")
> Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
> ---
> drivers/clk/at91/clk-sam9x60-pll.c | 12 +++++++++++-
> drivers/clk/at91/sam9x60.c | 2 +-
> 2 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clk/at91/clk-sam9x60-pll.c b/drivers/clk/at91/clk-sam9x60-pll.c
> index dfb91c190bd1..00f2afd6e9b6 100644
> --- a/drivers/clk/at91/clk-sam9x60-pll.c
> +++ b/drivers/clk/at91/clk-sam9x60-pll.c
> @@ -21,6 +21,9 @@
> #define UPLL_DIV 2
> #define PLL_MUL_MAX (FIELD_GET(PMC_PLL_CTRL1_MUL_MSK, UINT_MAX) + 1)
>
> +#define FCORE_MIN (600000000)
> +#define FCORE_MAX (1200000000)
> +
> #define PLL_MAX_ID 1
>
> struct sam9x60_pll {
> @@ -169,6 +172,7 @@ static long sam9x60_pll_get_best_div_mul(struct sam9x60_pll *pll,
> unsigned long bestdiv = 0;
> unsigned long bestmul = 0;
> unsigned long bestfrac = 0;
> + unsigned long long fcore = 0;

maybe it would be best to go for u64 here as this is what you cast into
later.

>
> if (rate < characteristics->output[0].min ||
> rate > characteristics->output[0].max)
> @@ -213,6 +217,11 @@ static long sam9x60_pll_get_best_div_mul(struct sam9x60_pll *pll,
> remainder = rate - tmprate;
> }
>
> + fcore = parent_rate * (tmpmul + 1) +
> + ((u64)parent_rate * tmpfrac >> 22);
> + if (fcore < FCORE_MIN || fcore > FCORE_MAX)
> + continue;
> +
> /*
> * Compare the remainder with the best remainder found until
> * now and elect a new best multiplier/divider pair if the
> @@ -232,7 +241,8 @@ static long sam9x60_pll_get_best_div_mul(struct sam9x60_pll *pll,
> }
>
> /* Check if bestrate is a valid output rate */
> - if (bestrate < characteristics->output[0].min ||
> + if (fcore < FCORE_MIN || fcore > FCORE_MAX ||
> + bestrate < characteristics->output[0].min ||
> bestrate > characteristics->output[0].max)
> return -ERANGE;
>
> diff --git a/drivers/clk/at91/sam9x60.c b/drivers/clk/at91/sam9x60.c
> index 3e20aa68259f..633891b98d43 100644
> --- a/drivers/clk/at91/sam9x60.c
> +++ b/drivers/clk/at91/sam9x60.c
> @@ -22,7 +22,7 @@ static const struct clk_master_layout sam9x60_master_layout = {
> };
>
> static const struct clk_range plla_outputs[] = {
> - { .min = 300000000, .max = 600000000 },
> + { .min = 2343750, .max = 1200000000 },
> };
>
> static const struct clk_pll_characteristics plla_characteristics = {
> --
> 2.7.4
>

--
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering