886d29bcd8
The function to read board IDs from tristate GPIOs currently supports two output modes: a normal base-3 integer, or a custom format where every two bits represent one tristate pin. Each board decides which representation to use on its own, which is inconsistent and provides another possible gotcha to trip over when reading unfamiliar code. The two-bits-per-pin format creates the additional problem that a complete list of IDs (such as some boards use to build board-ID tables) necessarily has "holes" in them (since 0b11 does not correspond to a possible pin state), which makes them extremely tricky to write, read and expand. It's also very unintuitive in my opinion, although it was intended to make it easier to read individual pin states from a hex representation. This patch switches all boards over to base-3 and removes the other format to improve consistency. The tristate reading function will just print the pin states as they are read to make it easier to debug them, and we add a new BASE3() macro that can generate ternary numbers from pin states. Also change the order of all static initializers of board ID pin lists to write the most significant bit first, hoping that this can help clear up confusion about the endianness of the pins. CQ-DEPEND=CL:219902 BUG=None TEST=Booted on a Nyan_Blaze (with board ID 1, unfortunately the only one I have). Compiled on Daisy, Peach_Pit, Nyan, Nyan_Big, Nyan_Blaze, Rush, Rush_Ryu, Storm, Veryon_Pinky and Falco for good measure. Change-Id: I3ce5a0829f260db7d7df77e6788c2c6d13901b8f Signed-off-by: Patrick Georgi <pgeorgi@chromium.org> Original-Commit-Id: 2fa9545ac431c9af111ee4444d593ee4cf49554d Original-Change-Id: I6133cdaf01ed6590ae07e88d9e85a33dc013211a Original-Signed-off-by: Julius Werner <jwerner@chromium.org> Original-Reviewed-on: https://chromium-review.googlesource.com/219901 Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org> Reviewed-on: http://review.coreboot.org/9401 Tested-by: build bot (Jenkins) Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
83 lines
2.3 KiB
C
83 lines
2.3 KiB
C
/*
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* This file is part of the coreboot project.
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*
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* Copyright 2014 Google Inc.
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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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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <base3.h>
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#include <console/console.h>
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#include <delay.h>
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#include <gpio.h>
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int gpio_get_tristates(gpio_t gpio[], int num_gpio)
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{
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/*
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* GPIOs which are tied to stronger external pull up or pull down
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* will stay there regardless of the internal pull up or pull
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* down setting.
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*
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* GPIOs which are floating will go to whatever level they're
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* internally pulled to.
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*/
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static const char tristate_char[] = {[0] = '0', [1] = '1', [Z] = 'Z'};
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int temp;
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int index;
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int id = 0;
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char value[num_gpio];
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/* Enable internal pull up */
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for (index = 0; index < num_gpio; ++index)
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gpio_input_pullup(gpio[index]);
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/* Wait until signals become stable */
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udelay(10);
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/* Get gpio values at internal pull up */
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for (index = 0; index < num_gpio; ++index)
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value[index] = gpio_get(gpio[index]);
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/* Enable internal pull down */
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for (index = 0; index < num_gpio; ++index)
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gpio_input_pulldown(gpio[index]);
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/* Wait until signals become stable */
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udelay(10);
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/*
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* Get gpio values at internal pull down.
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* Compare with gpio pull up value and then
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* determine a gpio final value/state:
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* 0: pull down
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* 1: pull up
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* 2: floating
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*/
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printk(BIOS_DEBUG, "Reading tristate GPIOs: ");
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for (index = num_gpio - 1; index >= 0; --index) {
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temp = gpio_get(gpio[index]);
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temp |= ((value[index] ^ temp) << 1);
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printk(BIOS_DEBUG, "%c ", tristate_char[temp]);
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id = (id * 3) + temp;
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}
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printk(BIOS_DEBUG, "= %d\n", id);
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/* Disable pull up / pull down to conserve power */
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for (index = 0; index < num_gpio; ++index)
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gpio_input(gpio[index]);
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return id;
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}
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