allwinner: Add a msgbox driver for use with SCPI

The function names follow the naming convention used by the existing
ARM SCPI client.
Signed-off-by: Samuel Holland <samuel@sholland.org>
Change-Id: I543bae7d46e206eb405dbedfcf7aeba88a12ca48

drivers/allwinner/sunxi_msgbox.c

+/*
+ * Copyright (c) 2017-2019, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <assert.h>
+#include <stdbool.h>
+
+#include <drivers/delay_timer.h>
+#include <lib/bakery_lock.h>
+#include <lib/mmio.h>
+#include <lib/utils_def.h>
+
+#include <sunxi_mmap.h>
+
+#define REMOTE_IRQ_EN_REG	0x0040
+#define REMOTE_IRQ_STAT_REG	0x0050
+#define LOCAL_IRQ_EN_REG	0x0060
+#define LOCAL_IRQ_STAT_REG	0x0070
+
+#define RX_IRQ(n)		BIT(0 + 2 * (n))
+#define TX_IRQ(n)		BIT(1 + 2 * (n))
+
+#define FIFO_STAT_REG(n)	(0x0100 + 0x4 * (n))
+#define FIFO_STAT_MASK		GENMASK(0, 0)
+
+#define MSG_STAT_REG(n)		(0x0140 + 0x4 * (n))
+#define MSG_STAT_MASK		GENMASK(2, 0)
+
+#define MSG_DATA_REG(n)		(0x0180 + 0x4 * (n))
+
+#define RX_CHAN			1
+#define TX_CHAN			0
+
+#define MHU_MAX_SLOT_ID		31
+
+#define MHU_TIMEOUT_DELAY	10
+#define MHU_TIMEOUT_ITERS	10000
+
+static DEFINE_BAKERY_LOCK(mhu_secure_message_lock);
+
+static bool sunxi_msgbox_last_tx_done(unsigned int chan)
+{
+	uint32_t stat = mmio_read_32(SUNXI_MSGBOX_BASE + REMOTE_IRQ_STAT_REG);
+
+	return (stat & RX_IRQ(chan)) == 0U;
+}
+
+static bool sunxi_msgbox_peek_data(unsigned int chan)
+{
+	uint32_t stat = mmio_read_32(SUNXI_MSGBOX_BASE + MSG_STAT_REG(chan));
+
+	return (stat & MSG_STAT_MASK) != 0U;
+}
+
+void mhu_secure_message_start(unsigned int slot_id __unused)
+{
+	uint32_t timeout = MHU_TIMEOUT_ITERS;
+
+	bakery_lock_get(&mhu_secure_message_lock);
+
+	/* Wait for all previous messages to be acknowledged. */
+	while (!sunxi_msgbox_last_tx_done(TX_CHAN) && --timeout)
+		udelay(MHU_TIMEOUT_DELAY);
+}
+
+void mhu_secure_message_send(unsigned int slot_id)
+{
+	mmio_write_32(SUNXI_MSGBOX_BASE + MSG_DATA_REG(TX_CHAN), BIT(slot_id));
+}
+
+uint32_t mhu_secure_message_wait(void)
+{
+	uint32_t timeout = MHU_TIMEOUT_ITERS;
+	uint32_t msg = 0;
+
+	/* Wait for a message from the SCP. */
+	while (!sunxi_msgbox_peek_data(RX_CHAN) && --timeout)
+		udelay(MHU_TIMEOUT_DELAY);
+
+	/* Return the most recent message in the FIFO. */
+	while (sunxi_msgbox_peek_data(RX_CHAN))
+		msg = mmio_read_32(SUNXI_MSGBOX_BASE + MSG_DATA_REG(RX_CHAN));
+
+	return msg;
+}
+
+void mhu_secure_message_end(unsigned int slot_id)
+{
+	/* Acknowledge a response by clearing the IRQ status. */
+	mmio_write_32(SUNXI_MSGBOX_BASE + LOCAL_IRQ_STAT_REG, RX_IRQ(RX_CHAN));
+
+	bakery_lock_release(&mhu_secure_message_lock);
+}

plat/allwinner/common/allwinner-common.mk

@@ -20,6 +20,7 @@ PLAT_BL_COMMON_SOURCES	:=	drivers/ti/uart/${ARCH}/16550_console.S	\
 				${AW_PLAT}/common/sunxi_common.c
 
 BL31_SOURCES		+=	drivers/allwinner/axp/common.c		\
+				drivers/allwinner/sunxi_msgbox.c	\
 				drivers/arm/gic/common/gic_common.c	\
 				drivers/arm/gic/v2/gicv2_helpers.c	\
 				drivers/arm/gic/v2/gicv2_main.c		\