4d6ef0da41
According to Spec for SKL+: "Isochronous Priority Control.
If enabled, Display sends demoted requests once the transition
watermark is reached. If transition watermark is not enabled,
Display sends demoted requests when the display buffer is full."
The commit 'e57f1c02155f ("drm/i915/gen9+: Add has_ipc flag in
device info structure")' introduced that as gen9+ but missing many
SKL Skus.
I believe the reason for that is Spec also mentions workarounds for
SKL-ALL: "IPC (Isoch Priority Control) may cause underflows
WA: Do not enable IPC in register ARB_CTL2"
It seems lame to add the feature and forever disable it,
but it will avoid a mistake of enabling it when we are reorganizing
the feature definitions on i915_pci.c later.
It will also allow us to probably extend that workaround for
other platforms.
Cc: Mahesh Kumar <mahesh1.kumar@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Mahesh Kumar <mahesh1.kumar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171003063652.17248-1-rodrigo.vivi@intel.com
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.