diff options
Diffstat (limited to 'Documentation/gpu/zynqmp.rst')
| -rw-r--r-- | Documentation/gpu/zynqmp.rst | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/Documentation/gpu/zynqmp.rst b/Documentation/gpu/zynqmp.rst new file mode 100644 index 000000000000..f57bfa0ad6ec --- /dev/null +++ b/Documentation/gpu/zynqmp.rst @@ -0,0 +1,149 @@ +.. 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 + + 80bit-custom + A custom 80-bit pattern + + cp2520 + HBR2 compliance eye pattern + + tps1 + Link training symbol pattern TPS1 (/D10.2/) + + tps2 + Link training symbol pattern TPS2 + + tps3 + Link training symbol pattern TPS3 (for HBR2) + +rate: + Rate in hertz. One of + + * 5400000000 (HBR2) + * 2700000000 (HBR) + * 1620000000 (RBR) + +You can dump the displayport test settings with the following command:: + + for prop in /sys/kernel/debug/dri/1/DP-1/test/*; do + printf '%-17s ' ${prop##*/} + if [ ${prop##*/} = custom ]; then + hexdump -C $prop | head -1 + else + cat $prop + fi + done + +The output could look something like:: + + active 1 + custom 00000000 00 00 00 00 00 00 00 00 00 00 |..........| + downspread 0 + enhanced 1 + ignore_aux_errors 1 + ignore_hpd 1 + lane0_preemphasis 0 + lane0_swing 3 + lane1_preemphasis 0 + lane1_swing 3 + lanes 2 + pattern prbs7 + rate 1620000000 + +The recommended test procedure is to connect the board to a monitor, +configure test mode, activate test mode, and then disconnect the cable +and connect it to your test equipment of choice. For example, one +sequence of commands could be:: + + echo 1 > /sys/kernel/debug/dri/1/DP-1/test/enhanced + echo tps1 > /sys/kernel/debug/dri/1/DP-1/test/pattern + echo 1620000000 > /sys/kernel/debug/dri/1/DP-1/test/rate + echo 1 > /sys/kernel/debug/dri/1/DP-1/test/ignore_aux_errors + echo 1 > /sys/kernel/debug/dri/1/DP-1/test/ignore_hpd + echo 1 > /sys/kernel/debug/dri/1/DP-1/test/active + +at which point the cable could be disconnected from the monitor. + +Internals +--------- + +.. kernel-doc:: drivers/gpu/drm/xlnx/zynqmp_disp.h + +.. kernel-doc:: drivers/gpu/drm/xlnx/zynqmp_dpsub.h + +.. kernel-doc:: drivers/gpu/drm/xlnx/zynqmp_kms.h + +.. kernel-doc:: drivers/gpu/drm/xlnx/zynqmp_disp.c + +.. kernel-doc:: drivers/gpu/drm/xlnx/zynqmp_dp.c + +.. kernel-doc:: drivers/gpu/drm/xlnx/zynqmp_dpsub.c + +.. kernel-doc:: drivers/gpu/drm/xlnx/zynqmp_kms.c |