bdeb18dbcf
EHL has a mux on combo PHY A that allows it to be driven either by an internal display (DDI-A or DSI DPHY) or by an external display (DDI-D). This is a motherboard design decision that can not be changed on the fly. Unfortunately there are no strap registers that allow us to detect the board configuration directly, so let's use the VBT to try to figure it out and program the mux accordingly. For now if we run across a broken VBT that tries to claim that PHY A is attached to both internal and external displays at the same time, we'll resolve the conflict in favor of the internal display. To help debug these kind of bad VBT's, let's also add a quick DRM_DEBUG message during child device parsing so that it's easier to understand these cases if they show up in bug reports. v2: - Confirmed that VBT's dvo port refers to the DDI and not the PHY. Thus we can check more explicitly for (ddi_d && !(ddi_a || dsi)). If a bad VBT contradicts itself, let internal display win. (Ville) v3: - Switch condition from !IS_ICELAKE to IS_ELKHARTLAKE. Although the convention is usually to assume that future platforms will inherit all current platform behavior, this feels more like a one-platform quirk. (Ville) - Update commit message to describe what we do if/when we encounter broken VBT's, and note that the new debug print during child device parsing is intentional. Cc: Clint Taylor <Clinton.A.Taylor@intel.com> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Signed-off-by: Matt Roper <matthew.d.roper@intel.com> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190618175131.9139-1-matthew.d.roper@intel.com |
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README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.