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74d11d37e2
This adds a serial driver which uses semihosting calls to read and write to the host's console. For convenience, if CONFIG_DM_SERIAL is enabled, we will instantiate a serial driver. This allows users to enable this driver (which has no physical device) without modifying their device trees or board files. We also implement a non-DM driver for SPL, or for much faster output in U-Boot proper. There are three ways to print to the console: Method Baud ================== ===== smh_putc in a loop 170 smh_puts 1600 smh_write with :tt 20000 ================== ===== These speeds were measured using a 175 character message with a J-Link adapter. For reference, U-Boot typically prints around 2700 characters during boot on this board. There are two major factors affecting the speed of these functions. First, each breakpoint incurs a delay. Second, each debugger memory transaction incurs a delay. smh_putc has a breakpoint and memory transaction for every character. smh_puts has one breakpoint, but still has to use a transaction for every character. This is because we don't know the length up front, so OpenOCD has to check if each character is nul. smh_write has only one breakpoint and one memory transfer. DM serial drivers can only implement a putc interface, so we are stuck with the slowest API. Non-DM drivers can implement puts, which is vastly more efficient. When the driver starts up, we try to open :tt. Since this is an extension, this may fail. If it does, we fall back to smh_puts. We don't check :semihosting-features, since there are nonconforming implementations (OpenOCD) which don't implement it (but *do* implement :tt). Some semihosting implementations (QEMU) don't handle READC properly. To work around this, we try to use open/read (much like for stdin) if possible. There is no non-blocking I/O available, so we don't implement pending. This will cause __serial_tstc to always return true. If CONFIG_SERIAL_RX_BUFFER is enabled, _serial_tstc will try and read characters forever. To avoid this, we depend on this config being disabled. Signed-off-by: Sean Anderson <sean.anderson@seco.com> Reviewed-by: Simon Glass <sjg@chromium.org>
147 lines
2.5 KiB
C
147 lines
2.5 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* Copyright (C) 2022 Sean Anderson <sean.anderson@seco.com>
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*/
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#include <common.h>
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#include <dm.h>
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#include <serial.h>
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#include <semihosting.h>
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/**
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* struct smh_serial_priv - Semihosting serial private data
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* @infd: stdin file descriptor (or error)
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*/
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struct smh_serial_priv {
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int infd;
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int outfd;
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};
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#if CONFIG_IS_ENABLED(DM_SERIAL)
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static int smh_serial_getc(struct udevice *dev)
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{
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char ch = 0;
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struct smh_serial_priv *priv = dev_get_priv(dev);
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if (priv->infd < 0)
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return smh_getc();
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smh_read(priv->infd, &ch, sizeof(ch));
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return ch;
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}
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static int smh_serial_putc(struct udevice *dev, const char ch)
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{
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smh_putc(ch);
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return 0;
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}
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static const struct dm_serial_ops smh_serial_ops = {
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.putc = smh_serial_putc,
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.getc = smh_serial_getc,
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};
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static int smh_serial_probe(struct udevice *dev)
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{
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struct smh_serial_priv *priv = dev_get_priv(dev);
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priv->infd = smh_open(":tt", MODE_READ);
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return 0;
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}
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U_BOOT_DRIVER(smh_serial) = {
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.name = "serial_semihosting",
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.id = UCLASS_SERIAL,
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.probe = smh_serial_probe,
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.priv_auto = sizeof(struct smh_serial_priv),
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.ops = &smh_serial_ops,
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.flags = DM_FLAG_PRE_RELOC,
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};
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U_BOOT_DRVINFO(smh_serial) = {
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.name = "serial_semihosting",
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};
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#else /* DM_SERIAL */
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static int infd = -ENODEV;
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static int outfd = -ENODEV;
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static int smh_serial_start(void)
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{
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infd = smh_open(":tt", MODE_READ);
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outfd = smh_open(":tt", MODE_WRITE);
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return 0;
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}
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static int smh_serial_stop(void)
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{
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if (outfd >= 0)
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smh_close(outfd);
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return 0;
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}
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static void smh_serial_setbrg(void)
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{
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}
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static int smh_serial_getc(void)
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{
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char ch = 0;
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if (infd < 0)
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return smh_getc();
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smh_read(infd, &ch, sizeof(ch));
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return ch;
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}
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static int smh_serial_tstc(void)
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{
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return 1;
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}
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static void smh_serial_puts(const char *s)
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{
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ulong unused;
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if (outfd < 0)
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smh_puts(s);
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else
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smh_write(outfd, s, strlen(s), &unused);
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}
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struct serial_device serial_smh_device = {
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.name = "serial_smh",
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.start = smh_serial_start,
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.stop = smh_serial_stop,
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.setbrg = smh_serial_setbrg,
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.getc = smh_serial_getc,
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.tstc = smh_serial_tstc,
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.putc = smh_putc,
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.puts = smh_serial_puts,
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};
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void smh_serial_initialize(void)
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{
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serial_register(&serial_smh_device);
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}
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__weak struct serial_device *default_serial_console(void)
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{
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return &serial_smh_device;
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}
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#endif
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#ifdef CONFIG_DEBUG_UART_SEMIHOSTING
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#include <debug_uart.h>
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static inline void _debug_uart_init(void)
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{
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}
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static inline void _debug_uart_putc(int c)
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{
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smh_putc(c);
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}
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DEBUG_UART_FUNCS
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#endif
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