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coreboot-kgpe-d16/src/drivers/uart/util.c

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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>
2014-02-17 18:37:52 +01:00
/*
* This file is part of the coreboot project.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2 of the License.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <console/console.h>
console: Fix includes Do not pull in console hw-specific prototypes everywhere with console.h as those are not needed for higher levels. Move prototypes for UARTs next to other consoles. Change-Id: Icbc9cd3e5bdfdab85d7dccd7c3827bba35248fb8 Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com> Reviewed-on: http://review.coreboot.org/5232 Tested-by: build bot (Jenkins) Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com> Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net> Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
2014-02-17 20:34:42 +01:00
#include <console/uart.h>
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>
2014-02-17 18:37:52 +01:00
#if CONFIG_USE_OPTION_TABLE
option: Add arch-agnostic get_option() We should not have pc80/ includes in console/. Change-Id: Id7da732b1ea094be01f45f9dbb49142f4e78f095 Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com> Reviewed-on: http://review.coreboot.org/5157 Tested-by: build bot (Jenkins) Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
2014-01-28 09:02:53 +01:00
#include <option.h>
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>
2014-02-17 18:37:52 +01:00
#include "option_table.h"
#endif
unsigned int default_baudrate(void)
{
#if !defined(__SMM__) && CONFIG_USE_OPTION_TABLE
static const unsigned baud[8] =
{ 115200, 57600, 38400, 19200, 9600, 4800, 2400, 1200 };
unsigned b_index = 0;
#if defined(__PRE_RAM__)
b_index = read_option(baud_rate, 0xff);
#else
if (get_option(&b_index, "baud_rate") != CB_SUCCESS)
b_index = 0xff;
#endif
if (b_index < 8)
return baud[b_index];
#endif
return CONFIG_TTYS0_BAUD;
}
/* Calculate divisor. Do not floor but round to nearest integer. */
unsigned int uart_baudrate_divisor(unsigned int baudrate,
unsigned int refclk, unsigned int oversample)
{
return (1 + (2 * refclk) / (baudrate * oversample)) / 2;
}
drivers/uart: Enable override for input clock divider Allow the platform to override the input clock divider by adding the uart_input_clock_divider routine. This routine combines the baud-rate oversample divider with any other input clock divider. The default routine returns 16 which is the standard baud-rate oversampling value. A platform may override this default "weak" routine by providing a new routine and selecting UART_OVERRIDE_INPUT_CLOCK_DIVIDER. This works around ROMCC not supporting weak routines. Testing on Galileo: * Edit the src/mainboard/intel/galileo/Makefile.inc file: * Add "select ADD_FSP_PDAT_FILE" * Add "select ADD_FSP_RAW_BIN" * Add "select ADD_RMU_FILE" * Place the FSP.bin file in the location specified by CONFIG_FSP_FILE * Place the pdat.bin files in the location specified by CONFIG_FSP_PDAT_FILE * Place the rmu.bin file in the location specified by CONFIG_RMU_FILE * Build EDK2 CorebootPayloadPkg/CorebootPayloadPkgIa32.dsc to generate UEFIPAYLOAD.fd * Testing is successful when CorebootPayloadPkg is able to properly initialize the serial port without using built-in values. Change-Id: Ieb6453b045d84702b8f730988d0fed9f253f63e2 Signed-off-by: Lee Leahy <leroy.p.leahy@intel.com> Reviewed-on: https://review.coreboot.org/14611 Tested-by: build bot (Jenkins) Reviewed-by: Martin Roth <martinroth@google.com>
2016-05-04 22:13:20 +02:00
#if !IS_ENABLED(CONFIG_UART_OVERRIDE_INPUT_CLOCK_DIVIDER)
unsigned int uart_input_clock_divider(void)
{
/* Specify the default oversample rate for the UART.
*
* UARTs oversample the receive data. The UART's input clock first
* enters the baud-rate divider to generate the oversample clock. Then
* the UART typically divides the result by 16. The asynchronous
* receive data is synchronized with the oversample clock and when a
* start bit is detected the UART delays half a bit time using the
* oversample clock. Samples are then taken to verify the start bit and
* if present, samples are taken for the rest of the frame.
*/
return 16;
}
#endif
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