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b29078e401
There have been discussions about removing this since it does not seem to be used much and only creates troubles for boards without defaults, not to mention that it was configurable on many boards that do not even feature uart. It is still possible to configure the baudrate through the Kconfig option. Change-Id: I71698d9b188eeac73670b18b757dff5fcea0df41 Signed-off-by: Arthur Heymans <arthur@aheymans.xyz> Reviewed-on: https://review.coreboot.org/19682 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Nico Huber <nico.h@gmx.de>
56 lines
2.0 KiB
C
56 lines
2.0 KiB
C
/*
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* This file is part of the coreboot project.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; version 2 of the License.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#include <console/console.h>
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#include <console/uart.h>
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/* Calculate divisor. Do not floor but round to nearest integer. */
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unsigned int uart_baudrate_divisor(unsigned int baudrate,
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unsigned int refclk, unsigned int oversample)
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{
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return (1 + (2 * refclk) / (baudrate * oversample)) / 2;
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}
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#if !IS_ENABLED(CONFIG_UART_OVERRIDE_INPUT_CLOCK_DIVIDER)
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unsigned int uart_input_clock_divider(void)
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{
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/* Specify the default oversample rate for the UART.
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*
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* UARTs oversample the receive data. The UART's input clock first
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* enters the baud-rate divider to generate the oversample clock. Then
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* the UART typically divides the result by 16. The asynchronous
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* receive data is synchronized with the oversample clock and when a
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* start bit is detected the UART delays half a bit time using the
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* oversample clock. Samples are then taken to verify the start bit and
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* if present, samples are taken for the rest of the frame.
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*/
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return 16;
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}
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#endif
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#if !IS_ENABLED(CONFIG_UART_OVERRIDE_REFCLK)
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unsigned int uart_platform_refclk(void)
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{
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/* Specify the default input clock frequency for the UART.
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*
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* The older UART's used an input clock frequency of 1.8432 MHz which
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* with the 16x oversampling provided the maximum baud-rate of 115200.
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* Specify this as maximum baud-rate multiplied by oversample so that
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* it is obvious that the maximum baud rate is 115200 when divided by
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* oversample clock. Also note that crystal on the board does not
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* change when software selects another input clock divider.
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*/
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return 115200 * 16;
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}
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#endif
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