plat/qemu: Add LPC based RTC support

This adds a driver for standard CMOS RTC chips and use it from
the QEMU platform.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

1 files changed, 239 insertions, 0 deletions

diff --git a/hw/lpc-rtc.c b/hw/lpc-rtc.c
new file mode 100644
index 0000000..63124df
--- /dev/null
+++ b/hw/lpc-rtc.c
@@ -0,0 +1,239 @@
+/* Copyright 2015 IBM Corp.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * 	http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+ * implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <ipmi.h>
+#include <time.h>
+#include <time-utils.h>
+#include <device.h>
+#include <opal.h>
+#include <rtc.h>
+#include <lpc.h>
+#include <lock.h>
+#include <timebase.h>
+
+/* Legacy RTC registers */
+#define RTC_REG_SECONDS		0
+#define RTC_REG_MINUTES		2
+#define RTC_REG_HOURS		4
+#define RTC_REG_DAY_OF_WEEK	6
+#define RTC_REG_DAY_OF_MONTH	7
+#define RTC_REG_MONTH		8
+#define RTC_REG_YEAR		9
+#define RTC_REG_A		10
+#define   RTC_REG_A_UIP			0x80
+#define RTC_REG_B		11
+#define   RTC_REG_B_DIS_UPD		0x80
+#define   RTC_REG_B_PIE			0x40
+#define   RTC_REG_B_AIE			0x20
+#define   RTC_REG_B_UIE			0x10
+#define   RTC_REG_B_SQWE		0x08
+#define   RTC_REG_B_DM_BINARY		0x04
+#define   RTC_REG_B_24H			0x02
+#define   RTC_REG_B_DST_EN		0x01
+#define RTC_REG_C		12
+#define RTC_REG_D		13
+#define   RTC_REG_D_VALID		0x80
+
+/* Init value is no interrupts, 24H mode, updates enabled */
+#define RTC_REG_B_INIT		(RTC_REG_B_24H)
+
+static u32 rtc_port;
+static struct lock rtc_lock = LOCK_UNLOCKED;
+
+static uint8_t rtc_read(uint8_t reg)
+{
+	lpc_outb(reg, rtc_port);
+	return lpc_inb(rtc_port + 1);
+}
+
+static void rtc_write(uint8_t reg, uint8_t val)
+{
+	lpc_outb(reg, rtc_port);
+	lpc_outb(val, rtc_port + 1);
+}
+
+static bool lpc_rtc_read_tm(struct tm *tm)
+{
+	struct tm tm2;
+	unsigned int loops = 0;
+
+	/* Read until two series provide identical values, this
+	 * should deal with update races in all practical cases
+	 */
+	for (;;) {
+		tm2 = *tm;
+		tm->tm_sec = rtc_read(RTC_REG_SECONDS);
+		tm->tm_min = rtc_read(RTC_REG_MINUTES);
+		tm->tm_hour = rtc_read(RTC_REG_HOURS);
+		tm->tm_mday = rtc_read(RTC_REG_DAY_OF_MONTH);
+		tm->tm_mon = rtc_read(RTC_REG_MONTH);
+		tm->tm_year = rtc_read(RTC_REG_YEAR);
+		if (loops > 0 && memcmp(&tm2, tm, sizeof(struct tm)) == 0)
+			break;
+		loops++;
+		if (loops > 10) {
+			prerror("RTC: Failed to obtain stable values\n");
+			return false;
+		}
+	}
+	tm->tm_sec = bcd_byte(tm->tm_sec, 0);
+	tm->tm_min = bcd_byte(tm->tm_min, 0);
+	tm->tm_hour = bcd_byte(tm->tm_hour, 0);
+	tm->tm_mday = bcd_byte(tm->tm_mday, 0);
+	tm->tm_mon = bcd_byte(tm->tm_mon, 0) - 1;
+	tm->tm_year = bcd_byte(tm->tm_year, 0);
+
+	/* 2000 wrap */
+	if (tm->tm_year < 69)
+		tm->tm_year += 100;
+
+	/* Base */
+	tm->tm_year += 1900;
+
+	return true;
+}
+
+static void lpc_rtc_write_tm(struct tm *tm __unused)
+{
+	/* XXX */
+}
+
+static void lpc_init_time(void)
+{
+	uint8_t val;
+	struct tm tm;
+	bool valid;
+
+	lock(&rtc_lock);
+
+	/* If update is in progress, wait a bit */
+	val = rtc_read(RTC_REG_A);
+	if (val & RTC_REG_A_UIP)
+		time_wait_ms(10);
+
+	/* Read from RTC */
+	valid = lpc_rtc_read_tm(&tm);
+
+	unlock(&rtc_lock);
+
+	/* Update cache */
+	if (valid)
+		rtc_cache_update(&tm);
+}
+
+static void lpc_init_hw(void)
+{
+	lock(&rtc_lock);
+
+	/* Set REG B to a suitable default */
+	rtc_write(RTC_REG_B, RTC_REG_B_INIT);
+
+	unlock(&rtc_lock);
+}
+
+static int64_t lpc_opal_rtc_read(uint32_t *y_m_d,
+				 uint64_t *h_m_s_m)
+{
+	uint8_t val;
+	int64_t rc = OPAL_SUCCESS;
+	struct tm tm;
+
+	if (!y_m_d || !h_m_s_m)
+		return OPAL_PARAMETER;
+
+	/* Return busy if updating. This is somewhat racy, but will
+	 * do for now, most RTCs nowadays are smart enough to atomically
+	 * update. Alternatively we could just read from the cache...
+	 */
+	lock(&rtc_lock);
+	val = rtc_read(RTC_REG_A);
+	if (val & RTC_REG_A_UIP) {
+		unlock(&rtc_lock);
+		return OPAL_BUSY_EVENT;
+	}
+
+	/* Read from RTC */
+	if (lpc_rtc_read_tm(&tm))
+		rc = OPAL_SUCCESS;
+	else
+		rc = OPAL_HARDWARE;
+	unlock(&rtc_lock);
+
+	if (rc == OPAL_SUCCESS) {
+		/* Update cache */
+		rtc_cache_update(&tm);
+
+		/* Convert to OPAL time */
+		tm_to_datetime(&tm, y_m_d, h_m_s_m);
+	}
+
+	return rc;
+}
+
+static int64_t lpc_opal_rtc_write(uint32_t year_month_day,
+				  uint64_t hour_minute_second_millisecond)
+{
+	struct tm tm;
+
+	/* Convert to struct tm */
+	datetime_to_tm(year_month_day, hour_minute_second_millisecond, &tm);
+
+	/* Write it out */
+	lock(&rtc_lock);
+	lpc_rtc_write_tm(&tm);
+	unlock(&rtc_lock);
+
+	return OPAL_SUCCESS;
+}
+
+void lpc_rtc_init(void)
+{
+	struct dt_node *rtc_node, *np;
+
+	if (!lpc_present())
+		return;
+
+	/* We support only one */
+	rtc_node = dt_find_compatible_node(dt_root, NULL, "pnpPNP,b00");
+	if (!rtc_node)
+		return;
+
+	/* Get IO base */
+	rtc_port = dt_prop_get_cell_def(rtc_node, "reg", 1, 0);
+	if (!rtc_port) {
+		prerror("RTC: Can't find reg property\n");
+		return;
+	}
+	if (dt_prop_get_cell_def(rtc_node, "reg", 0, 0) != OPAL_LPC_IO) {
+		prerror("RTC: Unsupported address type\n");
+		return;
+	}
+
+	/* Init the HW */
+	lpc_init_hw();
+
+	/* Create OPAL API node and register OPAL calls */
+	np = dt_new(opal_node, "rtc");
+	dt_add_property_strings(np, "compatible", "ibm,opal-rtc");
+
+	opal_register(OPAL_RTC_READ, lpc_opal_rtc_read, 2);
+	opal_register(OPAL_RTC_WRITE, lpc_opal_rtc_write, 2);
+
+	/* Initialise the rtc cache */
+	lpc_init_time();
+}