diff options
| author | Kyösti Mälkki <kyosti.malkki@gmail.com> | 2014-02-17 19:37:52 +0200 |
|---|---|---|
| committer | Kyösti Mälkki <kyosti.malkki@gmail.com> | 2014-03-04 15:22:08 +0100 |
| commit | 3ee1668ab4fbf75b256ac8eef4273b1ea445c998 (patch) | |
| tree | 59f35a43b85c5da6a0d9d38aba7f391971cbc980 /src/lib/uart8250.c | |
| parent | c76b3d6cca4a6135e5a7d7f3c2d9aa5128ef23f0 (diff) | |
uart8250: Fix and unify baudrate divisor calculation
Divisor is a function of requested baudrate, platform-specific
reference clock and amount of oversampling done on the UART reference.
Calculate this parameter with divisor rounded to nearest integer.
When building without option_table or when there is no entry for
baud_rate, CONFIG_TTYS0_BAUD is used for default baudrate.
For OxPCIe use of 4 MHz for reference was arbitrary giving correct
divisor for 115200 but somewhat inaccurate for lower baudrates.
Actual hardware is 62500000 with 16 times oversampling.
FIXME: Field for baudrate in lb_tables is still incorrect.
Change-Id: I68539738469af780fadd3392263dd9b3d5964d2d
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/5229
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Diffstat (limited to 'src/lib/uart8250.c')
| -rw-r--r-- | src/lib/uart8250.c | 35 |
1 files changed, 9 insertions, 26 deletions
diff --git a/src/lib/uart8250.c b/src/lib/uart8250.c index c9075a227a..d136eb8867 100644 --- a/src/lib/uart8250.c +++ b/src/lib/uart8250.c @@ -21,15 +21,16 @@ #include <arch/io.h> #include <uart.h> #include <uart8250.h> -#include <pc80/mc146818rtc.h> #include <trace.h> -#if CONFIG_USE_OPTION_TABLE -#include "option_table.h" -#endif - /* Should support 8250, 16450, 16550, 16550A type UARTs */ +/* Nominal values only, good for the range of choices Kconfig offers for + * set of standard baudrates. + */ +#define BAUDRATE_REFCLK (115200) +#define BAUDRATE_OVERSAMPLE (1) + /* Expected character delay at 1200bps is 9ms for a working UART * and no flow-control. Assume UART as stuck if shift register * or FIFO takes more than 50ms per character to appear empty. @@ -108,26 +109,8 @@ void uart8250_init(unsigned base_port, unsigned divisor) void uart_init(void) { - /* TODO the divisor calculation is hard coded to standard UARTs. Some - * UARTs won't work with these values. This should be a property of the - * UART used, worst case a Kconfig variable. For now live with hard - * codes as the only devices that might be different are the iWave - * iRainbowG6 and the OXPCIe952 card (and the latter is memory mapped) - */ - unsigned int div = (115200 / CONFIG_TTYS0_BAUD); - -#if !defined(__SMM__) && CONFIG_USE_OPTION_TABLE - static const unsigned char divisor[8] = { 1, 2, 3, 6, 12, 24, 48, 96 }; - unsigned b_index = 0; -#if defined(__PRE_RAM__) - b_index = read_option(baud_rate, 0); - b_index &= 7; - div = divisor[b_index]; -#else - if (get_option(&b_index, "baud_rate") == CB_SUCCESS) - div = divisor[b_index]; -#endif -#endif - + unsigned int div; + div = uart_baudrate_divisor(default_baudrate(), BAUDRATE_REFCLK, + BAUDRATE_OVERSAMPLE); uart8250_init(CONFIG_TTYS0_BASE, div); } |