On Tue, May 30, 2017 at 8:40 PM, Pandiyan, Dhinakaran < dhinakaran.pandi...@intel.com> wrote:
> The patch looks good overall, it would have been easier to merge if > you'd sent this as the first patch in this version. Some comments > inline. > > > Will re-order to make this the first patch in the next version. > > On Fri, 2017-05-26 at 18:42 -0700, Puthikorn Voravootivat wrote: > > Read desired PWM frequency from panel vbt and calculate the > > value for divider in DPCD address 0x724 and 0x728 to have > > as many bits as possible for PWM duty cyle for granularity of > > brightness adjustment while the frequency divisor is still > > within 25% of the desired value. > > > > Signed-off-by: Puthikorn Voravootivat <put...@chromium.org> > > --- > > drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 79 > +++++++++++++++++++++++++++ > > 1 file changed, 79 insertions(+) > > > > diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c > b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c > > index f55af41ce3bd..a8d485a29f29 100644 > > --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c > > +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c > > @@ -116,6 +116,81 @@ intel_dp_aux_set_dynamic_backlight_percent(struct > intel_dp *intel_dp, > > } > > } > > > > +/* > > + * Set PWM Frequency divider to match desired frequency in vbt. > > + * The PWM Frequency is calculated as 27Mhz / (F x P). > > + * - Where F = PWM Frequency Pre-Divider value programmed by field 7:0 > of the > > + * EDP_BACKLIGHT_FREQ_SET register (DPCD Address 00728h) > > + * - Where P = 2^Pn, where Pn is the value programmed by field 4:0 of > the > > + * EDP_PWMGEN_BIT_COUNT register (DPCD Address 00724h) > > + */ > > +static int intel_dp_aux_set_pwm_freq(struct intel_connector *connector) > > +{ > > + struct drm_i915_private *dev_priv = to_i915(connector->base.dev); > > + struct intel_dp *intel_dp = enc_to_intel_dp(&connector-> > encoder->base); > > + int freq, fxp, fxp_min, fxp_max, fxp_actual, f = 1; > > nit: unnecessary initialization for f? > No. We only set f in for (pn = pn_max; pn >= pn_min; pn--) but compiler wouldn't know that pn_max >= pn_min so f might be uninitialized. > > + u8 pn, pn_min, pn_max; > > + > > + /* Find desired value of (F x P) > > + * Note that, if F x P is out of supported range, the maximum > value or > > + * minimum value will applied automatically. So no need to check > that. > > + */ > > + freq = dev_priv->vbt.backlight.pwm_freq_hz; > > + DRM_DEBUG_KMS("VBT defined backlight frequency %u Hz\n", freq); > > + if (!freq) { > > + DRM_DEBUG_KMS("Use panel default backlight frequency\n"); > > + return -1; > > + } > > + > > + fxp = DIV_ROUND_CLOSEST(KHz(DP_EDP_BACKLIGHT_FREQ_BASE_KHZ), > freq); > > + > > + /* Use highest possible value of Pn for more granularity of > brightness > > + * adjustment while satifying the conditions below. > > + * - Pn is in the range of Pn_min and Pn_max > > + * - F is in the range of 1 and 255 > > + * - FxP is within 25% of desired value. > > + * Note: 25% is arbitrary value and may need some tweak. > > + */ > > + if (drm_dp_dpcd_readb(&intel_dp->aux, > > + DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, &pn_min) > != 1) { > > + DRM_DEBUG_KMS("Failed to read pwmgen bit count cap min\n"); > > + return -EIO; > > The error numbers are not propagated outside, so I don't see a real need > for them. bool should suffice. > > Sure. > > > + } > > + if (drm_dp_dpcd_readb(&intel_dp->aux, > > + DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX, &pn_max) > != 1) { > > + DRM_DEBUG_KMS("Failed to read pwmgen bit count cap max\n"); > > + return -EIO; > > + } > > + pn_min &= DP_EDP_PWMGEN_BIT_COUNT_MASK; > > + pn_max &= DP_EDP_PWMGEN_BIT_COUNT_MASK; > > + > > + fxp_min = DIV_ROUND_CLOSEST(fxp * 3, 4); > > + fxp_max = DIV_ROUND_CLOSEST(fxp * 5, 4); > > + if (fxp_min < (1 << pn_min) || (255 << pn_max) < fxp_max) { > > + DRM_DEBUG_KMS("VBT defined backlight frequency out of > range\n"); > > + return -ERANGE; > > + } > > + > > + for (pn = pn_max; pn >= pn_min; pn--) { > > + f = clamp(DIV_ROUND_CLOSEST(fxp, 1 << pn), 1, 255); > > + fxp_actual = f << pn; > > + if (fxp_min <= fxp_actual && fxp_actual <= fxp_max) > > + break; > > + } > > + > > + if (drm_dp_dpcd_writeb(&intel_dp->aux, > > + DP_EDP_PWMGEN_BIT_COUNT, pn) < 0) { > > + DRM_DEBUG_KMS("Failed to write aux pwmgen bit count\n"); > > + return -EIO; > > + } > > + if (drm_dp_dpcd_writeb(&intel_dp->aux, > > + DP_EDP_BACKLIGHT_FREQ_SET, (u8) f) < 0) { > > + DRM_DEBUG_KMS("Failed to write aux backlight freq\n"); > > + return -EIO; > > + } > > + return 0; > > +} > > + > > static void intel_dp_aux_enable_backlight(struct intel_connector > *connector) > > { > > struct intel_dp *intel_dp = enc_to_intel_dp(&connector-> > encoder->base); > > @@ -152,6 +227,10 @@ static void intel_dp_aux_enable_backlight(struct > intel_connector *connector) > > DRM_DEBUG_KMS("Enable dynamic brightness.\n"); > > } > > > > + if (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_FREQ_AUX_SET_CAP) > > + if (!intel_dp_aux_set_pwm_freq(connector)) > > nit: This doesn't read right to me, looking at the function name it > seems like you are proceeding when it failed. > > OK. > > > + new_dpcd_buf |= DP_EDP_BACKLIGHT_FREQ_AUX_SET_ > ENABLE; > > + > > if (new_dpcd_buf != dpcd_buf) { > > if (drm_dp_dpcd_writeb(&intel_dp->aux, > > DP_EDP_BACKLIGHT_MODE_SET_REGISTER, new_dpcd_buf) > < 0) { > >
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