Hi Marek,
On 03.12.2024 21:15, Marek Vasut wrote:
On 12/3/24 8:09 PM, Nikolaus Voss wrote:
LDB clock has to be a fixed multiple of the pixel clock.
As LDB and pixel clock are derived from different clock sources
Can you please share the content of /sys/kernel/debug/clk/clk_summary ?
Sure. Without my patch:
video_pll1_ref_sel 1 1 0 24000000
0 0 50000 Y deviceless
no_connection_id
video_pll1 1 1 0
1039500000 0 0 50000 Y deviceless
no_connection_id
video_pll1_bypass 1 1 0
1039500000 0 0 50000 Y deviceless
no_connection_id
video_pll1_out 2 2 0
1039500000 0 0 50000 Y deviceless
no_connection_id
media_ldb 1 1 0 346500000
0 0 50000 Y
32ec0000.blk-ctrl:bridge@5c ldb
deviceless
no_connection_id
media_ldb_root_clk 0 0 0
346500000 0 0 50000 Y deviceless
no_connection_id
media_disp2_pix 1 1 0 51975000
0 0 50000 Y deviceless
no_connection_id
media_disp2_pix_root_clk 1 1 0
51975000 0 0 50000 Y
32e90000.display-controller pix
Here 346500000 (media_ldb) != 7 * 51975000 (media_disp2_pix)
-> distorted panel image (if any).
The requested panel pixel clock from EDID is 51200000.
This is the same with my patch:
video_pll1_ref_sel 1 1 0 24000000
0 0 50000 Y deviceless
no_connection_id
video_pll1 1 1 0
1039500000 0 0 50000 Y deviceless
no_connection_id
video_pll1_bypass 1 1 0
1039500000 0 0 50000 Y deviceless
no_connection_id
video_pll1_out 2 2 0
1039500000 0 0 50000 Y deviceless
no_connection_id
media_ldb 1 1 0 346500000
0 0 50000 Y
32ec0000.blk-ctrl:bridge@5c ldb
deviceless
no_connection_id
media_ldb_root_clk 0 0 0
346500000 0 0 50000 Y deviceless
no_connection_id
media_disp2_pix 1 1 0 49500000
0 0 50000 Y deviceless
no_connection_id
media_disp2_pix_root_clk 1 1 0
49500000 0 0 50000 Y
32e90000.display-controller pix
So, here 346500000 (media_ldb) = 7 * 49500000 (media_disp2_pix).
-> stable panel image, but pixel clock reduced to 49.5 MHz from
requested 51.2 MHz.
My conclusion: The clock source is the same, nevertheless the
ldb/pixel clock constraint cannot be satisfied without either
modifying the pll clock or the pixel clock.
--
Nikolaus Voss
