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d50d7269eb
Add earlycon support for the arm/arm64 semihosting debug serial interface. This allows enabling a debug console when early_params are processed. This is based on the arm64 earlyprintk smh support and is intended to replace it. Signed-off-by: Rob Herring <robh@kernel.org> Cc: Jiri Slaby <jslaby@suse.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
62 lines
1.7 KiB
C
62 lines
1.7 KiB
C
/*
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* Copyright (C) 2012 ARM Ltd.
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* Author: Marc Zyngier <marc.zyngier@arm.com>
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*
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* Adapted for ARM and earlycon:
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* Copyright (C) 2014 Linaro Ltd.
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* Author: Rob Herring <robh@kernel.org>
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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 version 2 as
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* published by the Free Software Foundation.
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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, see <http://www.gnu.org/licenses/>.
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*/
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#include <linux/kernel.h>
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#include <linux/console.h>
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#include <linux/init.h>
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#include <linux/serial_core.h>
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#ifdef CONFIG_THUMB2_KERNEL
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#define SEMIHOST_SWI "0xab"
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#else
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#define SEMIHOST_SWI "0x123456"
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#endif
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/*
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* Semihosting-based debug console
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*/
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static void smh_putc(struct uart_port *port, int c)
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{
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#ifdef CONFIG_ARM64
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asm volatile("mov x1, %0\n"
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"mov x0, #3\n"
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"hlt 0xf000\n"
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: : "r" (&c) : "x0", "x1", "memory");
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#else
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asm volatile("mov r1, %0\n"
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"mov r0, #3\n"
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"svc " SEMIHOST_SWI "\n"
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: : "r" (&c) : "r0", "r1", "memory");
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#endif
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}
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static void smh_write(struct console *con, const char *s, unsigned n)
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{
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struct earlycon_device *dev = con->data;
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uart_console_write(&dev->port, s, n, smh_putc);
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}
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int __init early_smh_setup(struct earlycon_device *device, const char *opt)
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{
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device->con->write = smh_write;
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return 0;
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}
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EARLYCON_DECLARE(smh, early_smh_setup);
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