Good catch.
It will use default frequency in this case. But it is better to not set DP_EDP_BACKLIGHT_FREQ_AUX_SET_CAP in this case.
I will add return value to intel_dp_aux_set_pwm_freq() and set DP_EDP_BACKLIGHT_FREQ_AUX_SET_CAP based on that.
On Fri, May 26, 2017 at 5:49 AM, Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> wrote:
On Tue, 23 May 2017, Puthikorn Voravootivat <puthik@xxxxxxxxxxxx> 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.
IIUC this patch doesn't have a dependency on the more contentious
patches 2/5 and 3/5. This should probably be merged before them.
I share DK's concern about doing a bunch of reads and writes and
calculations every time the backlight's enabled. But I guess that could
be optimized later.
I haven't had time to check the changed algorithm here, but in the mean
time one comment below.
BR,
Jani.
What happens if there are any errors within that function, and it fails
>
> Signed-off-by: Puthikorn Voravootivat <puthik@xxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 82 +++++++++++++++++++++++++++
> 1 file changed, 82 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/intel_ dp_aux_backlight.c
> index f1b7855a2d2a..b7cd44550127 100644
> --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> @@ -116,10 +116,85 @@ 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 void 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;
> + 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;
> + }
> +
> + 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;
> + }
> + 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;
> + }
> + 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;
> + }
> +
> + 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;
> + }
> + 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;
> + }
> +}
> +
> static void intel_dp_aux_enable_backlight(struct intel_connector *connector)
> {
> struct intel_dp *intel_dp = enc_to_intel_dp(&connector->encoder->base);
> uint8_t dpcd_buf, new_dpcd_buf, edp_backlight_mode;
> + bool freq_cap;
>
> if (drm_dp_dpcd_readb(&intel_dp->aux,
> DP_EDP_BACKLIGHT_MODE_SET_REGISTER, &dpcd_buf) != 1) {
> @@ -152,6 +227,10 @@ static void intel_dp_aux_enable_backlight(struct intel_connector *connector)
> DRM_DEBUG_KMS("Enable dynamic brightness.\n");
> }
>
> + freq_cap = intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_FREQ_AUX_SET_CAP;
> + if (freq_cap)
> + 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) {
> @@ -159,6 +238,9 @@ static void intel_dp_aux_enable_backlight(struct intel_connector *connector)
> }
> }
>
> + if (freq_cap)
> + intel_dp_aux_set_pwm_freq(connector);
to write DP_EDP_BACKLIGHT_FREQ_SET, but
DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE has been set?
> +
> set_aux_backlight_enable(intel_dp, true); Jani Nikula, Intel Open Source Technology Center
> intel_dp_aux_set_backlight(connector, connector->panel.backlight. level);
> }
--
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