From 74d11d37e2d33c616748d5572fd5718944826d17 Mon Sep 17 00:00:00 2001 From: Sean Anderson Date: Tue, 22 Mar 2022 16:59:24 -0400 Subject: serial: Add semihosting driver 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 Reviewed-by: Simon Glass --- drivers/serial/Kconfig | 22 ++++++ drivers/serial/Makefile | 1 + drivers/serial/serial.c | 2 + drivers/serial/serial_semihosting.c | 147 ++++++++++++++++++++++++++++++++++++ 4 files changed, 172 insertions(+) create mode 100644 drivers/serial/serial_semihosting.c (limited to 'drivers') diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig index 610f8062c76..a07fab225fd 100644 --- a/drivers/serial/Kconfig +++ b/drivers/serial/Kconfig @@ -399,6 +399,15 @@ config DEBUG_UART_SANDBOX start up driver model. The driver will be available until the real driver model serial is running. +config DEBUG_UART_SEMIHOSTING + bool "semihosting" + depends on SEMIHOSTING_SERIAL + help + Select this to enable the debug UART using the semihosting driver. + This provides basic serial output from the console without needing to + start up driver model. The driver will be available until the real + driver model serial is running. + config DEBUG_UART_SIFIVE bool "SiFive UART" depends on SIFIVE_SERIAL @@ -782,6 +791,19 @@ config SCIF_CONSOLE on systems with RCar or SH SoCs, say Y to this option. If unsure, say N. +config SEMIHOSTING_SERIAL + bool "Semihosting UART support" + depends on SEMIHOSTING && !SERIAL_RX_BUFFER + help + Select this to enable a serial UART using semihosting. Special halt + instructions will be issued which an external debugger (such as a + JTAG emulator) may interpret. The debugger will display U-Boot's + console output on the host system. + + Enable this option only if you are using a debugger which supports + semihosting. If you are not using a debugger, this driver will halt + the boot. + config UNIPHIER_SERIAL bool "Support for UniPhier on-chip UART" depends on ARCH_UNIPHIER diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile index 52e70aa1917..b68b5e7b2bf 100644 --- a/drivers/serial/Makefile +++ b/drivers/serial/Makefile @@ -52,6 +52,7 @@ endif obj-$(CONFIG_XILINX_UARTLITE) += serial_xuartlite.o obj-$(CONFIG_SANDBOX_SERIAL) += sandbox.o obj-$(CONFIG_SCIF_CONSOLE) += serial_sh.o +obj-$(CONFIG_SEMIHOSTING_SERIAL) += serial_semihosting.o obj-$(CONFIG_ZYNQ_SERIAL) += serial_zynq.o obj-$(CONFIG_FSL_LPUART) += serial_lpuart.o obj-$(CONFIG_FSL_LINFLEXUART) += serial_linflexuart.o diff --git a/drivers/serial/serial.c b/drivers/serial/serial.c index ebbd21916d7..6cdbb89841c 100644 --- a/drivers/serial/serial.c +++ b/drivers/serial/serial.c @@ -126,6 +126,7 @@ serial_initfunc(mxc_serial_initialize); serial_initfunc(ns16550_serial_initialize); serial_initfunc(pl01x_serial_initialize); serial_initfunc(pxa_serial_initialize); +serial_initfunc(smh_serial_initialize); serial_initfunc(sh_serial_initialize); serial_initfunc(mtk_serial_initialize); @@ -180,6 +181,7 @@ int serial_initialize(void) ns16550_serial_initialize(); pl01x_serial_initialize(); pxa_serial_initialize(); + smh_serial_initialize(); sh_serial_initialize(); mtk_serial_initialize(); diff --git a/drivers/serial/serial_semihosting.c b/drivers/serial/serial_semihosting.c new file mode 100644 index 00000000000..7c7c5d94558 --- /dev/null +++ b/drivers/serial/serial_semihosting.c @@ -0,0 +1,147 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Copyright (C) 2022 Sean Anderson + */ + +#include +#include +#include +#include + +/** + * struct smh_serial_priv - Semihosting serial private data + * @infd: stdin file descriptor (or error) + */ +struct smh_serial_priv { + int infd; + int outfd; +}; + +#if CONFIG_IS_ENABLED(DM_SERIAL) +static int smh_serial_getc(struct udevice *dev) +{ + char ch = 0; + struct smh_serial_priv *priv = dev_get_priv(dev); + + if (priv->infd < 0) + return smh_getc(); + + smh_read(priv->infd, &ch, sizeof(ch)); + return ch; +} + +static int smh_serial_putc(struct udevice *dev, const char ch) +{ + smh_putc(ch); + return 0; +} + +static const struct dm_serial_ops smh_serial_ops = { + .putc = smh_serial_putc, + .getc = smh_serial_getc, +}; + +static int smh_serial_probe(struct udevice *dev) +{ + struct smh_serial_priv *priv = dev_get_priv(dev); + + priv->infd = smh_open(":tt", MODE_READ); + return 0; +} + +U_BOOT_DRIVER(smh_serial) = { + .name = "serial_semihosting", + .id = UCLASS_SERIAL, + .probe = smh_serial_probe, + .priv_auto = sizeof(struct smh_serial_priv), + .ops = &smh_serial_ops, + .flags = DM_FLAG_PRE_RELOC, +}; + +U_BOOT_DRVINFO(smh_serial) = { + .name = "serial_semihosting", +}; +#else /* DM_SERIAL */ +static int infd = -ENODEV; +static int outfd = -ENODEV; + +static int smh_serial_start(void) +{ + infd = smh_open(":tt", MODE_READ); + outfd = smh_open(":tt", MODE_WRITE); + return 0; +} + +static int smh_serial_stop(void) +{ + if (outfd >= 0) + smh_close(outfd); + return 0; +} + +static void smh_serial_setbrg(void) +{ +} + +static int smh_serial_getc(void) +{ + char ch = 0; + + if (infd < 0) + return smh_getc(); + + smh_read(infd, &ch, sizeof(ch)); + return ch; +} + +static int smh_serial_tstc(void) +{ + return 1; +} + +static void smh_serial_puts(const char *s) +{ + ulong unused; + + if (outfd < 0) + smh_puts(s); + else + smh_write(outfd, s, strlen(s), &unused); +} + +struct serial_device serial_smh_device = { + .name = "serial_smh", + .start = smh_serial_start, + .stop = smh_serial_stop, + .setbrg = smh_serial_setbrg, + .getc = smh_serial_getc, + .tstc = smh_serial_tstc, + .putc = smh_putc, + .puts = smh_serial_puts, +}; + +void smh_serial_initialize(void) +{ + serial_register(&serial_smh_device); +} + +__weak struct serial_device *default_serial_console(void) +{ + return &serial_smh_device; +} +#endif + +#ifdef CONFIG_DEBUG_UART_SEMIHOSTING +#include + +static inline void _debug_uart_init(void) +{ +} + +static inline void _debug_uart_putc(int c) +{ + smh_putc(c); +} + +DEBUG_UART_FUNCS +#endif -- cgit v1.3.1 From 2332590c48ac15926d7ec23b0fa17b9ea4e305ed Mon Sep 17 00:00:00 2001 From: Sean Anderson Date: Tue, 22 Mar 2022 16:59:32 -0400 Subject: serial: smh: Initialize serial only if semihosting is enabled If semihosting is disabled, then the user has no debugger attached, and will not see any messages. Don't create a serial device in this instance, to (hopefully) fall back on another working serial device. Signed-off-by: Sean Anderson --- drivers/serial/serial_semihosting.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'drivers') diff --git a/drivers/serial/serial_semihosting.c b/drivers/serial/serial_semihosting.c index 7c7c5d94558..62b1b2241b3 100644 --- a/drivers/serial/serial_semihosting.c +++ b/drivers/serial/serial_semihosting.c @@ -41,6 +41,13 @@ static const struct dm_serial_ops smh_serial_ops = { .getc = smh_serial_getc, }; +static int smh_serial_bind(struct udevice *dev) +{ + if (semihosting_enabled()) + return 0; + return -ENOENT; +} + static int smh_serial_probe(struct udevice *dev) { struct smh_serial_priv *priv = dev_get_priv(dev); @@ -52,6 +59,7 @@ static int smh_serial_probe(struct udevice *dev) U_BOOT_DRIVER(smh_serial) = { .name = "serial_semihosting", .id = UCLASS_SERIAL, + .bind = smh_serial_bind, .probe = smh_serial_probe, .priv_auto = sizeof(struct smh_serial_priv), .ops = &smh_serial_ops, @@ -122,7 +130,8 @@ struct serial_device serial_smh_device = { void smh_serial_initialize(void) { - serial_register(&serial_smh_device); + if (semihosting_enabled()) + serial_register(&serial_smh_device); } __weak struct serial_device *default_serial_console(void) -- cgit v1.3.1 From 7a763471894feb58d5a1bdf78ea7014c7a952264 Mon Sep 17 00:00:00 2001 From: Sean Anderson Date: Tue, 22 Mar 2022 16:59:34 -0400 Subject: serial: dm: Add support for puts Some serial drivers can be vastly more efficient when printing multiple characters at once. Non-DM serial has had a puts option for these sorts of drivers; implement it for DM serial as well. Because we have to add carriage returns, we can't just pass the whole string directly to the serial driver. Instead, we print up to the newline, then print a carriage return, and then continue on. This is less efficient, but it is better than printing each character individually. It also avoids having to allocate memory just to add a few characters. Drivers may perform short writes (such as filling a FIFO) and return the number of characters written in len. We loop over them in the same way that _serial_putc loops over putc. This results in around sizeof(void *) growth for all boards with DM_SERIAL. The full implementation takes around 140 bytes. Signed-off-by: Sean Anderson Reviewed-by: Simon Glass --- drivers/serial/Kconfig | 13 +++++++++++++ drivers/serial/serial-uclass.c | 26 ++++++++++++++++++++++++-- include/serial.h | 18 ++++++++++++++++++ 3 files changed, 55 insertions(+), 2 deletions(-) (limited to 'drivers') diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig index a07fab225fd..76171e7146a 100644 --- a/drivers/serial/Kconfig +++ b/drivers/serial/Kconfig @@ -133,6 +133,19 @@ config SERIAL_RX_BUFFER_SIZE help The size of the RX buffer (needs to be power of 2) +config SERIAL_PUTS + bool "Enable printing strings all at once" + depends on DM_SERIAL + help + Some serial drivers are much more efficient when printing multiple + characters at once rather than printing characters individually. This + can be because they can load a fifo, or because individual print + calls have a constant overhead. With this option set, the serial + subsystem will try to provide serial drivers with as many characters + at once as possible, instead of printing characters one by one. Most + serial drivers do not need this config to print efficiently. If + unsure, say N. + config SERIAL_SEARCH_ALL bool "Search for serial devices after default one failed" depends on DM_SERIAL diff --git a/drivers/serial/serial-uclass.c b/drivers/serial/serial-uclass.c index f30f352bd7a..10d6b800e2f 100644 --- a/drivers/serial/serial-uclass.c +++ b/drivers/serial/serial-uclass.c @@ -200,8 +200,30 @@ static void _serial_putc(struct udevice *dev, char ch) static void _serial_puts(struct udevice *dev, const char *str) { - while (*str) - _serial_putc(dev, *str++); + struct dm_serial_ops *ops = serial_get_ops(dev); + + if (!CONFIG_IS_ENABLED(SERIAL_PUTS) || !ops->puts) { + while (*str) + _serial_putc(dev, *str++); + return; + } + + do { + const char *newline = strchrnul(str, '\n'); + size_t len = newline - str + !!*newline; + + do { + ssize_t written = ops->puts(dev, str, len); + + if (written < 0) + return; + str += written; + len -= written; + } while (len); + + if (*newline) + _serial_putc(dev, '\r'); + } while (*str); } static int __serial_getc(struct udevice *dev) diff --git a/include/serial.h b/include/serial.h index 2681d26c829..8c2e7adbc32 100644 --- a/include/serial.h +++ b/include/serial.h @@ -195,6 +195,24 @@ struct dm_serial_ops { * @return 0 if OK, -ve on error */ int (*putc)(struct udevice *dev, const char ch); + /** + * puts() - Write a string + * + * This writes a string. This function should be implemented only if + * writing multiple characters at once is more performant than just + * calling putc() in a loop. + * + * If the whole string cannot be written at once, then this function + * should return the number of characters written. Returning a negative + * error code implies that no characters were written. If this function + * returns 0, then it will be called again with the same arguments. + * + * @dev: Device pointer + * @s: The string to write + * @len: The length of the string to write. + * @return The number of characters written on success, or -ve on error + */ + ssize_t (*puts)(struct udevice *dev, const char *s, size_t len); /** * pending() - Check if input/output characters are waiting * -- cgit v1.3.1