core/console.c

// SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
/*
 * Console IO routine for use by libc
 *
 * fd is the classic posix 0,1,2 (stdin, stdout, stderr)
 *
 * Copyright 2013-2018 IBM Corp.
 */

#include <skiboot.h>
#include <unistd.h>
#include <console.h>
#include <opal.h>
#include <device.h>
#include <processor.h>
#include <cpu.h>

static char *con_buf = (char *)INMEM_CON_START;
static size_t con_in;
static size_t con_out;
static bool con_wrapped;

/* Internal console driver ops */
static struct con_ops *con_driver;

/* External (OPAL) console driver ops */
static struct opal_con_ops *opal_con_driver = &dummy_opal_con;

static struct lock con_lock = LOCK_UNLOCKED;

/* This is mapped via TCEs so we keep it alone in a page */
struct memcons memcons __section(".data.memcons") = {
	.magic		= CPU_TO_BE64(MEMCONS_MAGIC),
	.obuf_phys	= CPU_TO_BE64(INMEM_CON_START),
	.ibuf_phys	= CPU_TO_BE64(INMEM_CON_START + INMEM_CON_OUT_LEN),
	.obuf_size	= CPU_TO_BE32(INMEM_CON_OUT_LEN),
	.ibuf_size	= CPU_TO_BE32(INMEM_CON_IN_LEN),
};

static bool dummy_console_enabled(void)
{
#ifdef FORCE_DUMMY_CONSOLE
	return true;
#else
	return dt_has_node_property(dt_chosen,
				    "sapphire,enable-dummy-console", NULL);
#endif
}

/*
 * Helper function for adding /ibm,opal/consoles/serial@<xyz> nodes
 */
struct dt_node *add_opal_console_node(int index, const char *type,
	uint32_t write_buffer_size)
{
	struct dt_node *con, *consoles;
	char buffer[32];

	consoles = dt_find_by_name(opal_node, "consoles");
	if (!consoles) {
		consoles = dt_new(opal_node, "consoles");
		assert(consoles);
		dt_add_property_cells(consoles, "#address-cells", 1);
		dt_add_property_cells(consoles, "#size-cells", 0);
	}

	con = dt_new_addr(consoles, "serial", index);
	assert(con);

	snprintf(buffer, sizeof(buffer), "ibm,opal-console-%s", type);
	dt_add_property_string(con, "compatible", buffer);

	dt_add_property_cells(con, "#write-buffer-size", write_buffer_size);
	dt_add_property_cells(con, "reg", index);
	dt_add_property_string(con, "device_type", "serial");

	return con;
}

void clear_console(void)
{
	memset(con_buf, 0, INMEM_CON_LEN);
}

/*
 * Flush the console buffer into the driver, returns true
 * if there is more to go.
 * Optionally can skip flushing to drivers, leaving messages
 * just in memory console.
 */
static bool __flush_console(bool flush_to_drivers, bool need_unlock)
{
	struct cpu_thread *cpu = this_cpu();
	size_t req, len = 0;
	static bool in_flush, more_flush;

	/* Is there anything to flush ? Bail out early if not */
	if (con_in == con_out || !con_driver)
		return false;

	/*
	 * Console flushing is suspended on this CPU, typically because
	 * some critical locks are held that would potentially cause a
	 * flush to deadlock
	 *
	 * Also if it recursed on con_lock (need_unlock is false). This
	 * can happen due to debug code firing (e.g., list or stack
	 * debugging).
	 */
	if (cpu->con_suspend || !need_unlock) {
		cpu->con_need_flush = true;
		return false;
	}
	cpu->con_need_flush = false;

	/*
	 * We must call the underlying driver with the console lock
	 * dropped otherwise we get some deadlocks if anything down
	 * that path tries to printf() something.
	 *
	 * So instead what we do is we keep a static in_flush flag
	 * set/released with the lock held, which is used to prevent
	 * concurrent attempts at flushing the same chunk of buffer
	 * by other processors.
	 */
	if (in_flush) {
		more_flush = true;
		return false;
	}
	in_flush = true;

	/*
	 * NB: this must appear after the in_flush check since it modifies
	 *     con_out.
	 */
	if (!flush_to_drivers) {
		con_out = con_in;
		in_flush = false;
		return false;
	}

	do {
		more_flush = false;

		if (con_out > con_in) {
			req = INMEM_CON_OUT_LEN - con_out;
			more_flush = true;
		} else
			req = con_in - con_out;

		unlock(&con_lock);
		len = con_driver->write(con_buf + con_out, req);
		lock(&con_lock);

		con_out = (con_out + len) % INMEM_CON_OUT_LEN;

		/* write error? */
		if (len < req)
			break;
	} while(more_flush);

	in_flush = false;
	return con_out != con_in;
}

bool flush_console(void)
{
	bool ret;

	lock(&con_lock);
	ret = __flush_console(true, true);
	unlock(&con_lock);

	return ret;
}

static void inmem_write(char c)
{
	uint32_t opos;

	if (!c)
		return;
	con_buf[con_in++] = c;
	if (con_in >= INMEM_CON_OUT_LEN) {
		con_in = 0;
		con_wrapped = true;
	}

	/*
	 * We must always re-generate memcons.out_pos because
	 * under some circumstances, the console script will
	 * use a broken putmemproc that does RMW on the full
	 * 8 bytes containing out_pos and in_prod, thus corrupting
	 * out_pos
	 */
	opos = con_in;
	if (con_wrapped)
		opos |= MEMCONS_OUT_POS_WRAP;
	lwsync();
	memcons.out_pos = cpu_to_be32(opos);

	/* If head reaches tail, push tail around & drop chars */
	if (con_in == con_out)
		con_out = (con_in + 1) % INMEM_CON_OUT_LEN;
}

static size_t inmem_read(char *buf, size_t req)
{
	size_t read = 0;
	char *ibuf = (char *)be64_to_cpu(memcons.ibuf_phys);

	while (req && be32_to_cpu(memcons.in_prod) != be32_to_cpu(memcons.in_cons)) {
		*(buf++) = ibuf[be32_to_cpu(memcons.in_cons)];
		lwsync();
		memcons.in_cons = cpu_to_be32((be32_to_cpu(memcons.in_cons) + 1) % INMEM_CON_IN_LEN);
		req--;
		read++;
	}
	return read;
}

static void write_char(char c)
{
#ifdef MAMBO_DEBUG_CONSOLE
	mambo_console_write(&c, 1);
#endif
	inmem_write(c);
}

ssize_t console_write(bool flush_to_drivers, const void *buf, size_t count)
{
	/* We use recursive locking here as we can get called
	 * from fairly deep debug path
	 */
	bool need_unlock = lock_recursive(&con_lock);
	const char *cbuf = buf;

	while(count--) {
		char c = *(cbuf++);
		if (c == '\n')
			write_char('\r');
		write_char(c);
	}

	__flush_console(flush_to_drivers, need_unlock);

	if (need_unlock)
		unlock(&con_lock);

	return count;
}

ssize_t write(int fd __unused, const void *buf, size_t count)
{
	return console_write(true, buf, count);
}

ssize_t read(int fd __unused, void *buf, size_t req_count)
{
	bool need_unlock = lock_recursive(&con_lock);
	size_t count = 0;

	if (con_driver && con_driver->read)
		count = con_driver->read(buf, req_count);
	if (!count)
		count = inmem_read(buf, req_count);
	if (need_unlock)
		unlock(&con_lock);
	return count;
}

/* Helper function to perform a full synchronous flush */
void console_complete_flush(void)
{
	/*
	 * Using term 0 here is a dumb hack that works because the UART
	 * only has term 0 and the FSP doesn't have an explicit flush method.
	 */
	int64_t ret = opal_con_driver->flush(0);

	if (ret == OPAL_UNSUPPORTED || ret == OPAL_PARAMETER)
		return;

	while (ret != OPAL_SUCCESS) {
		ret = opal_con_driver->flush(0);
	}
}

/*
 * set_console()
 *
 * This sets the driver used internally by Skiboot. This is different to the
 * OPAL console driver.
 */
void set_console(struct con_ops *driver)
{
	con_driver = driver;
	if (driver)
		flush_console();
}

/*
 * set_opal_console()
 *
 * Configure the console driver to handle the console provided by the OPAL API.
 * They are different to the above in that they are typically buffered, and used
 * by the host OS rather than skiboot.
 */
static bool opal_cons_init = false;

void set_opal_console(struct opal_con_ops *driver)
{
	assert(!opal_cons_init);
	opal_con_driver = driver;
}

void init_opal_console(void)
{
	assert(!opal_cons_init);
	opal_cons_init = true;

	if (dummy_console_enabled() && opal_con_driver != &dummy_opal_con) {
		prlog(PR_WARNING, "OPAL: Dummy console forced, %s ignored\n",
		      opal_con_driver->name);

		opal_con_driver = &dummy_opal_con;
	}

	prlog(PR_INFO, "OPAL: Using %s\n", opal_con_driver->name);

	if (opal_con_driver->init)
		opal_con_driver->init();

	opal_register(OPAL_CONSOLE_READ, opal_con_driver->read, 3);
	opal_register(OPAL_CONSOLE_WRITE, opal_con_driver->write, 3);
	opal_register(OPAL_CONSOLE_FLUSH, opal_con_driver->flush, 1);
	opal_register(OPAL_CONSOLE_WRITE_BUFFER_SPACE,
			opal_con_driver->space, 2);
}

void memcons_add_properties(void)
{
	dt_add_property_u64(opal_node, "ibm,opal-memcons", (u64) &memcons);
}

/*
 * The default OPAL console.
 *
 * In the absence of a "real" OPAL console driver we handle the OPAL_CONSOLE_*
 * calls by writing into the skiboot log buffer. Reads are a little more
 * complicated since they can come from the in-memory console (BML) or from the
 * internal skiboot console driver.
 */
static int64_t dummy_console_write(int64_t term_number, __be64 *length,
				   const uint8_t *buffer)
{
	uint64_t l;

	if (term_number != 0)
		return OPAL_PARAMETER;

	if (!opal_addr_valid(length) || !opal_addr_valid(buffer))
		return OPAL_PARAMETER;

	l = be64_to_cpu(*length);
	write(0, buffer, l);

	return OPAL_SUCCESS;
}

static int64_t dummy_console_write_buffer_space(int64_t term_number,
						__be64 *length)
{
	if (term_number != 0)
		return OPAL_PARAMETER;

	if (!opal_addr_valid(length))
		return OPAL_PARAMETER;

	if (length)
		*length = cpu_to_be64(INMEM_CON_OUT_LEN);

	return OPAL_SUCCESS;
}

static int64_t dummy_console_read(int64_t term_number, __be64 *length,
				  uint8_t *buffer)
{
	uint64_t l;

	if (term_number != 0)
		return OPAL_PARAMETER;

	if (!opal_addr_valid(length) || !opal_addr_valid(buffer))
		return OPAL_PARAMETER;

	l = be64_to_cpu(*length);
	l = read(0, buffer, l);
	*length = cpu_to_be64(l);
	opal_update_pending_evt(OPAL_EVENT_CONSOLE_INPUT, 0);

	return OPAL_SUCCESS;
}

static int64_t dummy_console_flush(int64_t term_number __unused)
{
	return OPAL_UNSUPPORTED;
}

static void dummy_console_poll(void *data __unused)
{
	bool has_data = false;

	lock(&con_lock);
	if (con_driver && con_driver->poll_read)
		has_data = con_driver->poll_read();
	if (memcons.in_prod != memcons.in_cons)
		has_data = true;
	if (has_data)
		opal_update_pending_evt(OPAL_EVENT_CONSOLE_INPUT,
					OPAL_EVENT_CONSOLE_INPUT);
	else
		opal_update_pending_evt(OPAL_EVENT_CONSOLE_INPUT, 0);
	unlock(&con_lock);
}

void dummy_console_add_nodes(void)
{
	struct dt_property *p;

	add_opal_console_node(0, "raw", be32_to_cpu(memcons.obuf_size));

	/* Mambo might have left a crap one, clear it */
	p = __dt_find_property(dt_chosen, "linux,stdout-path");
	if (p)
		dt_del_property(dt_chosen, p);

	dt_add_property_string(dt_chosen, "linux,stdout-path",
			       "/ibm,opal/consoles/serial@0");

	opal_add_poller(dummy_console_poll, NULL);
}

struct opal_con_ops dummy_opal_con = {
	.name = "Dummy Console",
	.init = dummy_console_add_nodes,
	.read = dummy_console_read,
	.write = dummy_console_write,
	.space = dummy_console_write_buffer_space,
	.flush = dummy_console_flush,
};