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authorAngel Pons <th3fanbus@gmail.com>2024-04-28 21:34:20 +0200
committerFelix Held <felix-coreboot@felixheld.de>2024-04-29 21:59:40 +0000
commit1fa0fcbd7b47dce6b7726e8a37e8294e899521c6 (patch)
tree36de895a52603ebf42688b98116e0977b5e6cb50 /Documentation
parent0b90b0fb053f88959a81bd01e6d9988d2c533363 (diff)
soc/intel/cmn/graphics: Make DDI-A 4 lanes configurable
As described in Intel document 336464 (8th gen S series datasheet volume 1), the CPU's 4 eDP lanes can be bifurcated, so that DDI-A (eDP) ends up with 2 lanes, and DDI-E (DP, typically used for VGA) has the remaining 2 lanes. This lets mainboards provide a VGA output without sacrificing one of the main 4-lane DDIs. Newer platforms seem to be lacking this. However, the way this is structured in coreboot does not allow boards to choose whether bifurcation should be enabled. Most boards in the tree do not use DDI-E (it doesn't exist on mobile platforms), but there are some boards (e.g. hp/280_g2) that use DDI-E and a DP-to-VGA converter chip to provide a VGA output. Replace `SOC_INTEL_CONFIGURE_DDI_A_4_LANES` with two new Kconfig options to allow boards to decide. Use `SOC_INTEL_GFX_HAVE_DDI_A_BIFURCATION` to specify whether a platform supports DDI-A bifurcation at all (do nothing otherwise, maintaining the original code's behaviour). If bifurcation is supported, the `SOC_INTEL_GFX_ENABLE_DDI_E_BIFURCATION` is used to clear or set the `DDI_A_4_LANES` bit in the `DDI_BUF_CTL_A` register. Change-Id: I516538db77509209d371f3f49c920476e06b052f Signed-off-by: Angel Pons <th3fanbus@gmail.com> Reviewed-on: https://review.coreboot.org/c/coreboot/+/82113 Reviewed-by: Nico Huber <nico.h@gmx.de> Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
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