shouldn't 1843200 be 18432000 (as in 18.432 MHz)? (I used this source clock a lot during my 8051 days a long time ago :) ) Koen On 2018-03-29 15:17, Eugeniy Paltsev wrote:
Hi Rafał, Hm, your 'port->uartclk' value (and therefore 'BASE_BAUD' value) looks strange to me... Looks like you have 'BASE_BAUD' set to 115200. Here is my example: uart clock is 33333333Hz (fixed 33.33MHz xtal clock) So 'BASE_BAUD' is 33333333/16 = 2083333 So 'port->uartclk' is BASE_BAUD*16 = 33333328 'device->baud' is 115200 (which is read from device tree) So when we calculate divisor with this code ------------------->8--------------- divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud); ------------------->8--------------- We got 'divisor' = 181 which is correct value for us. On Thu, 2018-03-29 at 14:34 +0200, Rafał Miłecki wrote:Hi, I upgraded my BCM5301X device based on BCM4708 SoC from 4.13 to 4.14 and noticed earlycon output is corrupted (a wrong baud rate is used). I bisected this problem down to the: commit 31cb9a8575ca04f47ea113434d4782b695638b62 Author: Eugeniy Paltsev <Eugeniy.Paltsev@xxxxxxxxxxxx> Date: Mon Aug 21 19:22:13 2017 +0300 earlycon: initialise baud field of earlycon device structure My device uses arch/arm/boot/dts/bcm4708.dtsi: uart0: serial@0300 { compatible = "ns16550"; reg = <0x0300 0x100>; interrupts = <GIC_SPI 85 IRQ_TYPE_LEVEL_HIGH>; clocks = <&iprocslow>; status = "okay"; }; aliases { serial0 = &uart0; }; chosen { stdout-path = "serial0:115200n8"; }; A valid UART divisor for my device is 54. This is what bootloader sets and what works with my serial console running 115200 8n1. Before the commit 31cb9a8575ca0 early_serial8250_setup() never tried setting baud because device->baud was 0. It left baud (divisor) to whatever was configured by the bootloader. It has changed with above commit though. So now the setup looks like that: 1) port->uartclk equals 1843200 as set in the of_setup_earlycon(): port->uartclk = BASE_BAUD * 16; 2) [NEW] device->baud equals 115200 as set in the of_setup_earlycon(): early_console_dev.baud = simple_strtoul(options, NULL, 0); (a value of options is "115200n8") 3) [NEW] divisor is calculated to 1 in the init_port(): divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud); 4) [NEW] divisor is set using UART_DLL and UART_DLM in the init_port() Obviously setting divisor 1 instead of 54 results in a wrong baud. So right now my serial console output looks like that: �6;'+{.��s�.���.".��4��.�����.��J|�.�.8��.�..������g��~.����L>.��,�9z9�{�Z�.."���NC�<�9.�/���.�.�}��~.���"�.�|����;?�.��yy�.[ 0.043623] console [ttyS0] enabled [ 0.043623] console [ttyS0] enabled [ 0.050842] bootconsole [ns16550] disabled [ 0.050842] bootconsole [ns16550] disabled [ 0.062939] libphy: Fixed MDIO Bus: probed (...) For a complete log (coming from dmesg command) see attachment. Can you take a look at this problem, please? Is there something wrong with my DT? Or is a problem in 8250 or earlycon?
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