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4a8d79901d
So-recently a bunch of laptops on the market have started using DPCD backlight controls instead of the traditional DDI backlight controls. Originally we thought we had this handled by adding VESA backlight control support to i915, but the story ended up being a lot more complicated then that. Simply put-there's two main backlight interfaces Intel can see in the wild. Intel's proprietary HDR backlight interface, and the standard VESA backlight interface. Note that many panels have been observed to report support for both backlight interfaces, but testing has shown far more panels work with the Intel HDR backlight interface at the moment. Additionally, the VBT appears to be capable of reporting support for the VESA backlight interface but not the Intel HDR interface which needs to be probed by setting the right magic OUI. On top of that however, there's also actually two different variants of the Intel HDR backlight interface. The first uses the AUX channel for controlling the brightness of the screen in both SDR and HDR mode, and the second only uses the AUX channel for setting the brightness level in HDR mode - relying on PWM for setting the brightness level in SDR mode. For the time being we've been using EDIDs to maintain a list of quirks for panels that safely do support the VESA backlight interface. Adding support for Intel's HDR backlight interface in addition however, should finally allow us to auto-detect eDP backlight controls properly so long as we probe like so: * If the panel's VBT reports VESA backlight support, assume it really does support it * If the panel's VBT reports DDI backlight controls: * First probe for Intel's HDR backlight interface * If that fails, probe for VESA's backlight interface * If that fails, assume no DPCD backlight control * If the panel's VBT reports any other backlight type: just assume it doesn't have DPCD backlight controls Changes since v4: * Fix checkpatch issues Changes since v3: * Stop using drm_device and use drm_i915_private instead * Don't forget to return from intel_dp_aux_hdr_get_backlight() if we fail to read the current backlight mode from the DPCD * s/uint8_t/u8/ * Remove unneeded parenthesis in intel_dp_aux_hdr_enable_backlight() * Use drm_dbg_kms() in intel_dp_aux_init_backlight_funcs() Signed-off-by: Lyude Paul <lyude@redhat.com> Reviewed-by: Jani Nikula <jani.nikula@intel.com> Cc: thaytan@noraisin.net Cc: Vasily Khoruzhick <anarsoul@gmail.com> Link: https://patchwork.freedesktop.org/patch/msgid/20210114221709.2261452-4-lyude@redhat.com |
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