[Intel-gfx] [PATCH v6 6/9] drm/i915/dpcd_bl: Return early in vesa_calc_max_backlight if we can't read PWMGEN_BIT_COUNT
From: Lyude Paul <lyude@redhat.com>
Date: 2021-05-14 18:16:09
Also in:
dri-devel, lkml, nouveau
Subsystem:
drm drivers, intel drm display for xe and i915 drivers, intel drm i915 driver (meteor lake, dg2 and older excluding poulsbo, moorestown and derivative), the rest · Maintainers:
David Airlie, Simona Vetter, Jani Nikula, Rodrigo Vivi, Joonas Lahtinen, Tvrtko Ursulin, Linus Torvalds
If we can't read DP_EDP_PWMGEN_BIT_COUNT in intel_dp_aux_vesa_calc_max_backlight() but do have a valid PWM frequency defined in the VBT, we'll keep going in the function until we inevitably fail on reading DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN. There's not much point in doing this, so just return early. Signed-off-by: Lyude Paul <lyude@redhat.com> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com> --- drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
index 781c7cd98d75..bf8e4ed56847 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c@@ -449,11 +449,14 @@ static u32 intel_dp_aux_vesa_calc_max_backlight(struct intel_connector *connecto int freq, fxp, fxp_min, fxp_max, fxp_actual, f = 1; u8 pn, pn_min, pn_max; - if (drm_dp_dpcd_readb(&intel_dp->aux, DP_EDP_PWMGEN_BIT_COUNT, &pn) == 1) { - pn &= DP_EDP_PWMGEN_BIT_COUNT_MASK; - max_backlight = (1 << pn) - 1; + if (drm_dp_dpcd_readb(&intel_dp->aux, DP_EDP_PWMGEN_BIT_COUNT, &pn) != 1) { + drm_dbg_kms(&i915->drm, "Failed to read pwmgen bit count cap\n"); + return 0; } + pn &= DP_EDP_PWMGEN_BIT_COUNT_MASK; + max_backlight = (1 << pn) - 1; + /* 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.
--
2.31.1
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