From 106b4a2a78b2a2f14885604891957b84bba502db Mon Sep 17 00:00:00 2001 From: Adrian Betschart Date: Fri, 11 Sep 2026 17:13:14 +0200 Subject: drm/amd/display: Try RGB before YCbCr 4:4:4 in stream validation amdgpu_dm_create_validate_stream_for_sink() walks encoding_order[] and uses the first encoding that validates. YCbCr 4:4:4 is listed before RGB, so an HDMI sink that advertises 4:4:4 gets YCbCr 4:4:4 whenever the "color format" property is left at AUTO, even though RGB fits the same link. That contradicts the documented AUTO behaviour for HDMI in enum drm_connector_color_format (RGB, falling back to YCbCr 4:2:0 only when the bandwidth is not available or the mode is 4:2:0-only), which the amdgpu implementation of the property also describes. It also leaves the "Broadcast RGB" property without effect on such sinks, since the quantization range it selects only applies to RGB output. Try RGB first. The mask still holds every encoding the sink supports, so a mode that cannot carry RGB falls back exactly as before. For reference, v7.2 picked RGB here unless YCbCr 4:4:4 was forced through debugfs, while earlier kernels picked YCbCr 4:4:4 for any HDMI sink that advertised it. Fixes: 0b0ff65d3ca1 ("drm/amd/display: Refactor stream validation") Suggested-by: Adolfo Rodrigues Assisted-by: Claude Code:claude-fable-5-1 Signed-off-by: Adrian Betschart Reviewed-by: Fangzhi Zuo Tested-by: Adolfo Rodrigues Tested-by: Daniel Wheeler Signed-off-by: Alex Deucher (cherry picked from commit 7de432bc753133764dc40d37f9388da56de251e7) --- .../admin-guide/auxdisplay/cfag12864b.rst | 98 ++++++++++++++++++++++ Documentation/admin-guide/auxdisplay/index.rst | 9 ++ Documentation/admin-guide/auxdisplay/ks0108.rst | 50 +++++++++++ 3 files changed, 157 insertions(+) create mode 100644 Documentation/admin-guide/auxdisplay/cfag12864b.rst create mode 100644 Documentation/admin-guide/auxdisplay/index.rst create mode 100644 Documentation/admin-guide/auxdisplay/ks0108.rst (limited to 'Documentation/admin-guide/auxdisplay') diff --git a/Documentation/admin-guide/auxdisplay/cfag12864b.rst b/Documentation/admin-guide/auxdisplay/cfag12864b.rst new file mode 100644 index 000000000..da385d851 --- /dev/null +++ b/Documentation/admin-guide/auxdisplay/cfag12864b.rst @@ -0,0 +1,98 @@ +=================================== +cfag12864b LCD Driver Documentation +=================================== + +:License: GPLv2 +:Author & Maintainer: Miguel Ojeda +:Date: 2006-10-27 + + + +.. INDEX + + 1. DRIVER INFORMATION + 2. DEVICE INFORMATION + 3. WIRING + 4. USERSPACE PROGRAMMING + +1. Driver Information +--------------------- + +This driver supports a cfag12864b LCD. + + +2. Device Information +--------------------- + +:Manufacturer: Crystalfontz +:Device Name: Crystalfontz 12864b LCD Series +:Device Code: cfag12864b +:Webpage: http://www.crystalfontz.com +:Device Webpage: http://www.crystalfontz.com/products/12864b/ +:Type: LCD (Liquid Crystal Display) +:Width: 128 +:Height: 64 +:Colors: 2 (B/N) +:Controller: ks0108 +:Controllers: 2 +:Pages: 8 each controller +:Addresses: 64 each page +:Data size: 1 byte each address +:Memory size: 2 * 8 * 64 * 1 = 1024 bytes = 1 Kbyte + + +3. Wiring +--------- + +The cfag12864b LCD Series don't have official wiring. + +The common wiring is done to the parallel port as shown:: + + Parallel Port cfag12864b + + Name Pin# Pin# Name + + Strobe ( 1)------------------------------(17) Enable + Data 0 ( 2)------------------------------( 4) Data 0 + Data 1 ( 3)------------------------------( 5) Data 1 + Data 2 ( 4)------------------------------( 6) Data 2 + Data 3 ( 5)------------------------------( 7) Data 3 + Data 4 ( 6)------------------------------( 8) Data 4 + Data 5 ( 7)------------------------------( 9) Data 5 + Data 6 ( 8)------------------------------(10) Data 6 + Data 7 ( 9)------------------------------(11) Data 7 + (10) [+5v]---( 1) Vdd + (11) [GND]---( 2) Ground + (12) [+5v]---(14) Reset + (13) [GND]---(15) Read / Write + Line (14)------------------------------(13) Controller Select 1 + (15) + Init (16)------------------------------(12) Controller Select 2 + Select (17)------------------------------(16) Data / Instruction + Ground (18)---[GND] [+5v]---(19) LED + + Ground (19)---[GND] + Ground (20)---[GND] E A Values: + Ground (21)---[GND] [GND]---[P1]---(18) Vee - R = Resistor = 22 ohm + Ground (22)---[GND] | - P1 = Preset = 10 Kohm + Ground (23)---[GND] ---- S ------( 3) V0 - P2 = Preset = 1 Kohm + Ground (24)---[GND] | | + Ground (25)---[GND] [GND]---[P2]---[R]---(20) LED - + + +4. Userspace Programming +------------------------ + +The cfag12864bfb describes a framebuffer device (/dev/fbX). + +It has a size of 1024 bytes = 1 Kbyte. +Each bit represents one pixel. If the bit is high, the pixel will +turn on. If the pixel is low, the pixel will turn off. + +You can use the framebuffer as a file: fopen, fwrite, fclose... +Although the LCD won't get updated until the next refresh time arrives. + +Also, you can mmap the framebuffer: open & mmap, munmap & close... +which is the best option for most uses. + +Check samples/auxdisplay/cfag12864b-example.c +for a real working userspace complete program with usage examples. diff --git a/Documentation/admin-guide/auxdisplay/index.rst b/Documentation/admin-guide/auxdisplay/index.rst new file mode 100644 index 000000000..31eae0825 --- /dev/null +++ b/Documentation/admin-guide/auxdisplay/index.rst @@ -0,0 +1,9 @@ +========================= +Auxiliary Display Support +========================= + +.. toctree:: + :maxdepth: 1 + + ks0108.rst + cfag12864b.rst diff --git a/Documentation/admin-guide/auxdisplay/ks0108.rst b/Documentation/admin-guide/auxdisplay/ks0108.rst new file mode 100644 index 000000000..a7d3fe509 --- /dev/null +++ b/Documentation/admin-guide/auxdisplay/ks0108.rst @@ -0,0 +1,50 @@ +========================================== +ks0108 LCD Controller Driver Documentation +========================================== + +:License: GPLv2 +:Author & Maintainer: Miguel Ojeda +:Date: 2006-10-27 + + + +.. INDEX + + 1. DRIVER INFORMATION + 2. DEVICE INFORMATION + 3. WIRING + + +1. Driver Information +--------------------- + +This driver supports the ks0108 LCD controller. + + +2. Device Information +--------------------- + +:Manufacturer: Samsung +:Device Name: KS0108 LCD Controller +:Device Code: ks0108 +:Webpage: - +:Device Webpage: - +:Type: LCD Controller (Liquid Crystal Display Controller) +:Width: 64 +:Height: 64 +:Colors: 2 (B/N) +:Pages: 8 +:Addresses: 64 each page +:Data size: 1 byte each address +:Memory size: 8 * 64 * 1 = 512 bytes + + +3. Wiring +--------- + +The driver supports data parallel port wiring. + +If you aren't building LCD related hardware, you should check +your LCD specific wiring information in the same folder. + +For example, check Documentation/admin-guide/auxdisplay/cfag12864b.rst -- cgit v1.3.1