Thank you for pointing to clk-bcm2835.c, it does look like the clock is configured here.
However I am still not sure how to change it using an overlay.
For the Pi5 it seems to be easier since clock management is handled by the RP1 chip which has a dedicated section in /dts/broadcom
/rp1.dtsi
For the BCM2711 I assume it should be done in /broadcom/bcm2711.dtsi but no rates are defined here.
I really would like to know how init_uart_clock worked but I cannot find any reference.
It should be possible to assign a different clock source to UART but knowing that init_uart_clock allowed custom clock rates, it must be possible somehow.
However I am still not sure how to change it using an overlay.
For the Pi5 it seems to be easier since clock management is handled by the RP1 chip which has a dedicated section in /dts/broadcom
/rp1.dtsi
Code:
rp1_clocks: clocks@18000 {compatible = "raspberrypi,rp1-clocks";#clock-cells = <1>;reg = <0xc0 0x40018000 0x0 0x10038>;clocks = <&clk_xosc>;assigned-clocks = <&rp1_clocks RP1_PLL_SYS_CORE>, <&rp1_clocks RP1_PLL_AUDIO_CORE>, // RP1_PLL_VIDEO_CORE and dividers are now managed by VEC,DPI drivers <&rp1_clocks RP1_PLL_SYS>, <&rp1_clocks RP1_PLL_SYS_SEC>, <&rp1_clocks RP1_PLL_AUDIO>, <&rp1_clocks RP1_PLL_AUDIO_SEC>, <&rp1_clocks RP1_CLK_SYS>, <&rp1_clocks RP1_PLL_SYS_PRI_PH>, // RP1_CLK_SLOW_SYS is used for the frequency counter (FC0) <&rp1_clocks RP1_CLK_SLOW_SYS>, <&rp1_clocks RP1_CLK_SDIO_TIMER>, <&rp1_clocks RP1_CLK_SDIO_ALT_SRC>, <&rp1_clocks RP1_CLK_ETH_TSU>;assigned-clock-rates = <1000000000>, // RP1_PLL_SYS_CORE <1536000000>, // RP1_PLL_AUDIO_CORE <200000000>, // RP1_PLL_SYS <125000000>, // RP1_PLL_SYS_SEC <61440000>, // RP1_PLL_AUDIO <192000000>, // RP1_PLL_AUDIO_SEC <200000000>, // RP1_CLK_SYS <100000000>, // RP1_PLL_SYS_PRI_PH // Must match the XOSC frequency <50000000>, // RP1_CLK_SLOW_SYS <1000000>, // RP1_CLK_SDIO_TIMER <200000000>, // RP1_CLK_SDIO_ALT_SRC <50000000>; // RP1_CLK_ETH_TSU};I really would like to know how init_uart_clock worked but I cannot find any reference.
It should be possible to assign a different clock source to UART but knowing that init_uart_clock allowed custom clock rates, it must be possible somehow.
Statistics: Posted by p0ckin3d — Thu Nov 21, 2024 8:56 am
