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With newer, more diverse hardware designs, the rclk can be unknown. Currently deployed systems have no standard way to discover the baud-clock generator frequency. However, sometimes we have a fairly good idea that the firmware programmed the UART to be the baud rate that it's telling us it's at. Create a way to instruct the uart class drivers to compute the baud clock frequency the first time their init routines are called. Usually the 'divisors' are relatively small, meaning we will likely have a fairly large error (goes as 1 / (divisor + 1). However, we also know that the baud-generator clock needs to be divided down to the baud-rate +/- about 5% (so while the error could be large for an arbitrary baud-clock, standard baud rates generally will give an error of 5% or less). Often, the console speed and the getty-configured speed are the same, so this heuristic allows boot messages and login sessions to work. Sponsored by: Netflix Reviewed by: andrew Differential Revision: https://reviews.freebsd.org/D47072 |
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| .. | ||
| uart.h | ||
| uart_bus.h | ||
| uart_bus_acpi.c | ||
| uart_bus_fdt.c | ||
| uart_bus_isa.c | ||
| uart_bus_pci.c | ||
| uart_bus_puc.c | ||
| uart_bus_scc.c | ||
| uart_core.c | ||
| uart_cpu.h | ||
| uart_cpu_acpi.c | ||
| uart_cpu_acpi.h | ||
| uart_cpu_arm64.c | ||
| uart_cpu_fdt.c | ||
| uart_cpu_fdt.h | ||
| uart_cpu_powerpc.c | ||
| uart_cpu_x86.c | ||
| uart_dbg.c | ||
| uart_dev_imx.c | ||
| uart_dev_imx.h | ||
| uart_dev_lowrisc.c | ||
| uart_dev_lowrisc.h | ||
| uart_dev_msm.c | ||
| uart_dev_msm.h | ||
| uart_dev_mu.c | ||
| uart_dev_mvebu.c | ||
| uart_dev_ns8250.c | ||
| uart_dev_ns8250.h | ||
| uart_dev_pl011.c | ||
| uart_dev_quicc.c | ||
| uart_dev_snps.c | ||
| uart_dev_ti8250.c | ||
| uart_dev_z8530.c | ||
| uart_if.m | ||
| uart_ppstypes.h | ||
| uart_subr.c | ||
| uart_tty.c | ||