diff options
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/clk/at91/clk-pll.c | 147 |
1 files changed, 77 insertions, 70 deletions
diff --git a/drivers/clk/at91/clk-pll.c b/drivers/clk/at91/clk-pll.c index 7b453b915c72..a1adcf186023 100644 --- a/drivers/clk/at91/clk-pll.c +++ b/drivers/clk/at91/clk-pll.c @@ -15,6 +15,7 @@ #include <linux/of_address.h> #include <linux/of_irq.h> #include <linux/io.h> +#include <linux/kernel.h> #include <linux/wait.h> #include <linux/sched.h> #include <linux/interrupt.h> @@ -29,6 +30,9 @@ #define PLL_DIV(reg) ((reg) & PLL_DIV_MASK) #define PLL_MUL(reg, layout) (((reg) >> (layout)->mul_shift) & \ (layout)->mul_mask) +#define PLL_MUL_MIN 2 +#define PLL_MUL_MASK(layout) ((layout)->mul_mask) +#define PLL_MUL_MAX(layout) (PLL_MUL_MASK(layout) + 1) #define PLL_ICPR_SHIFT(id) ((id) * 16) #define PLL_ICPR_MASK(id) (0xffff << PLL_ICPR_SHIFT(id)) #define PLL_MAX_COUNT 0x3f @@ -163,99 +167,102 @@ static long clk_pll_get_best_div_mul(struct clk_pll *pll, unsigned long rate, unsigned long parent_rate, u32 *div, u32 *mul, u32 *index) { - unsigned long maxrate; - unsigned long minrate; - unsigned long divrate; - unsigned long bestdiv = 1; - unsigned long bestmul; - unsigned long tmpdiv; - unsigned long roundup; - unsigned long rounddown; - unsigned long remainder; - unsigned long bestremainder; - unsigned long maxmul; - unsigned long maxdiv; - unsigned long mindiv; - int i = 0; const struct clk_pll_layout *layout = pll->layout; const struct clk_pll_characteristics *characteristics = pll->characteristics; + unsigned long bestremainder = ULONG_MAX; + unsigned long maxdiv, mindiv, tmpdiv; + long bestrate = -ERANGE; + unsigned long bestdiv; + unsigned long bestmul; + int i = 0; - /* Minimum divider = 1 */ - /* Maximum multiplier = max_mul */ - maxmul = layout->mul_mask + 1; - maxrate = (parent_rate * maxmul) / 1; - - /* Maximum divider = max_div */ - /* Minimum multiplier = 2 */ - maxdiv = PLL_DIV_MAX; - minrate = (parent_rate * 2) / maxdiv; - + /* Check if parent_rate is a valid input rate */ if (parent_rate < characteristics->input.min || - parent_rate < characteristics->input.max) - return -ERANGE; - - if (parent_rate < minrate || parent_rate > maxrate) + parent_rate > characteristics->input.max) return -ERANGE; - for (i = 0; i < characteristics->num_output; i++) { - if (parent_rate >= characteristics->output[i].min && - parent_rate <= characteristics->output[i].max) - break; - } - - if (i >= characteristics->num_output) - return -ERANGE; - - bestmul = rate / parent_rate; - rounddown = parent_rate % rate; - roundup = rate - rounddown; - bestremainder = roundup < rounddown ? roundup : rounddown; - - if (!bestremainder) { - if (div) - *div = bestdiv; - if (mul) - *mul = bestmul; - if (index) - *index = i; - return rate; - } - - maxdiv = 255 / (bestmul + 1); - if (parent_rate / maxdiv < characteristics->input.min) - maxdiv = parent_rate / characteristics->input.min; - mindiv = parent_rate / characteristics->input.max; - if (parent_rate % characteristics->input.max) - mindiv++; - - for (tmpdiv = mindiv; tmpdiv < maxdiv; tmpdiv++) { - divrate = parent_rate / tmpdiv; - - rounddown = rate % divrate; - roundup = divrate - rounddown; - remainder = roundup < rounddown ? roundup : rounddown; - + /* + * Calculate minimum divider based on the minimum multiplier, the + * parent_rate and the requested rate. + * Should always be 2 according to the input and output characteristics + * of the PLL blocks. + */ + mindiv = (parent_rate * PLL_MUL_MIN) / rate; + if (!mindiv) + mindiv = 1; + + /* + * Calculate the maximum divider which is limited by PLL register + * layout (limited by the MUL or DIV field size). + */ + maxdiv = DIV_ROUND_UP(parent_rate * PLL_MUL_MAX(layout), rate); + if (maxdiv > PLL_DIV_MAX) + maxdiv = PLL_DIV_MAX; + + /* + * Iterate over the acceptable divider values to find the best + * divider/multiplier pair (the one that generates the closest + * rate to the requested one). + */ + for (tmpdiv = mindiv; tmpdiv <= maxdiv; tmpdiv++) { + unsigned long remainder; + unsigned long tmprate; + unsigned long tmpmul; + + /* + * Calculate the multiplier associated with the current + * divider that provide the closest rate to the requested one. + */ + tmpmul = DIV_ROUND_CLOSEST(rate, parent_rate / tmpdiv); + tmprate = (parent_rate / tmpdiv) * tmpmul; + if (tmprate > rate) + remainder = tmprate - rate; + else + remainder = rate - tmprate; + + /* + * Compare the remainder with the best remainder found until + * now and elect a new best multiplier/divider pair if the + * current remainder is smaller than the best one. + */ if (remainder < bestremainder) { bestremainder = remainder; - bestmul = rate / divrate; bestdiv = tmpdiv; + bestmul = tmpmul; + bestrate = tmprate; } + /* + * We've found a perfect match! + * Stop searching now and use this multiplier/divider pair. + */ if (!remainder) break; } - rate = (parent_rate / bestdiv) * bestmul; + /* We haven't found any multiplier/divider pair => return -ERANGE */ + if (bestrate < 0) + return bestrate; + + /* Check if bestrate is a valid output rate */ + for (i = 0; i < characteristics->num_output; i++) { + if (bestrate >= characteristics->output[i].min && + bestrate <= characteristics->output[i].max) + break; + } + + if (i >= characteristics->num_output) + return -ERANGE; if (div) *div = bestdiv; if (mul) - *mul = bestmul; + *mul = bestmul - 1; if (index) *index = i; - return rate; + return bestrate; } static long clk_pll_round_rate(struct clk_hw *hw, unsigned long rate, |