Documentation/gpu/zynqmp.rst

Source file repositories/reference/linux-study-clean/Documentation/gpu/zynqmp.rst

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Linux kernel
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Documentation/gpu/zynqmp.rst
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.rst
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Support Tooling And Documentation
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Documentation
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Support Tooling And Documentation: documentation
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Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

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.. SPDX-License-Identifier: GPL-2.0+

===============================================
Xilinx ZynqMP Ultrascale+ DisplayPort Subsystem
===============================================

This subsystem handles DisplayPort video and audio output on the ZynqMP. It
supports in-memory framebuffers with the DisplayPort DMA controller
(xilinx-dpdma), as well as "live" video and audio from the programmable logic
(PL). This subsystem can perform several transformations, including color space
conversion, alpha blending, and audio mixing, although not all features are
currently supported.

debugfs
-------

To support debugging and compliance testing, several test modes can be enabled
though debugfs. The following files in /sys/kernel/debug/dri/X/DP-1/test/
control the DisplayPort test modes:

active:
        Writing a 1 to this file will activate test mode, and writing a 0 will
        deactivate test mode. Writing a 1 or 0 when the test mode is already
        active/inactive will re-activate/re-deactivate test mode. When test
        mode is inactive, changes made to other files will have no (immediate)
        effect, although the settings will be saved for when test mode is
        activated. When test mode is active, changes made to other files will
        apply immediately.

custom:
        Custom test pattern value

downspread:
        Enable/disable clock downspreading (spread-spectrum clocking) by
        writing 1/0

enhanced:
        Enable/disable enhanced framing

ignore_aux_errors:
        Ignore AUX errors when set to 1. Writes to this file take effect
        immediately (regardless of whether test mode is active) and affect all
        AUX transfers.

ignore_hpd:
        Ignore hotplug events (such as cable removals or monitor link
        retraining requests) when set to 1. Writes to this file take effect
        immediately (regardless of whether test mode is active).

laneX_preemphasis:
        Preemphasis from 0 (lowest) to 2 (highest) for lane X

laneX_swing:
        Voltage swing from 0 (lowest) to 3 (highest) for lane X

lanes:
        Number of lanes to use (1, 2, or 4)

pattern:
        Test pattern. May be one of:

                video
                        Use regular video input

                symbol-error
                        Symbol error measurement pattern

                prbs7
                        Output of the PRBS7 (x^7 + x^6 + 1) polynomial

Annotation

Implementation Notes