diff options
| -rw-r--r-- | drivers/gpu/drm/i915/intel_display.c | 50 |
1 files changed, 36 insertions, 14 deletions
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c index 3c91bd19987b..9dc9a85d0008 100644 --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -776,6 +776,33 @@ g4x_find_best_dpll(const intel_limit_t *limit, struct intel_crtc *crtc, return found; } +/* + * Check if the calculated PLL configuration is more optimal compared to the + * best configuration and error found so far. Return the calculated error. + */ +static bool vlv_PLL_is_optimal(struct drm_device *dev, int target_freq, + const intel_clock_t *calculated_clock, + const intel_clock_t *best_clock, + unsigned int best_error_ppm, + unsigned int *error_ppm) +{ + *error_ppm = div_u64(1000000ULL * + abs(target_freq - calculated_clock->dot), + target_freq); + /* + * Prefer a better P value over a better (smaller) error if the error + * is small. Ensure this preference for future configurations too by + * setting the error to 0. + */ + if (*error_ppm < 100 && calculated_clock->p > best_clock->p) { + *error_ppm = 0; + + return true; + } + + return *error_ppm + 10 < best_error_ppm; +} + static bool vlv_find_best_dpll(const intel_limit_t *limit, struct intel_crtc *crtc, int target, int refclk, intel_clock_t *match_clock, @@ -800,7 +827,7 @@ vlv_find_best_dpll(const intel_limit_t *limit, struct intel_crtc *crtc, clock.p = clock.p1 * clock.p2; /* based on hardware requirement, prefer bigger m1,m2 values */ for (clock.m1 = limit->m1.min; clock.m1 <= limit->m1.max; clock.m1++) { - unsigned int ppm, diff; + unsigned int ppm; clock.m2 = DIV_ROUND_CLOSEST(target * clock.p * clock.n, refclk * clock.m1); @@ -811,20 +838,15 @@ vlv_find_best_dpll(const intel_limit_t *limit, struct intel_crtc *crtc, &clock)) continue; - diff = abs(clock.dot - target); - ppm = div_u64(1000000ULL * diff, target); - - if (ppm < 100 && clock.p > best_clock->p) { - bestppm = 0; - *best_clock = clock; - found = true; - } + if (!vlv_PLL_is_optimal(dev, target, + &clock, + best_clock, + bestppm, &ppm)) + continue; - if (bestppm >= 10 && ppm < bestppm - 10) { - bestppm = ppm; - *best_clock = clock; - found = true; - } + *best_clock = clock; + bestppm = ppm; + found = true; } } } |