ARM: bcm2835: add mailbox driver

The BCM2835 SoC contains (at least) two CPUs; the VideoCore (a/k/a "GPU")
and the ARM CPU. The ARM CPU is often thought of as the main CPU.
However, the VideoCore actually controls the initial SoC boot, and hides
much of the hardware behind a protocol. This protocol is transported
using the SoC's mailbox hardware module.

Here, we add a very simplistic driver for the mailbox module, and define
a few structures for the property messages.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>

2 files changed, 165 insertions, 1 deletions

diff --git a/arch/arm/cpu/arm1176/bcm2835/Makefile b/arch/arm/cpu/arm1176/bcm2835/Makefile
index 95da6a8..135de42 100644
--- a/arch/arm/cpu/arm1176/bcm2835/Makefile
+++ b/arch/arm/cpu/arm1176/bcm2835/Makefile
@@ -17,7 +17,7 @@ include $(TOPDIR)/config.mk
 LIB	= $(obj)lib$(SOC).o
 
 SOBJS	:= lowlevel_init.o
-COBJS	:= init.o reset.o timer.o
+COBJS	:= init.o reset.o timer.o mbox.o
 
 SRCS	:= $(SOBJS:.o=.c) $(COBJS:.o=.c)
 OBJS	:= $(addprefix $(obj),$(SOBJS) $(COBJS))
diff --git a/arch/arm/cpu/arm1176/bcm2835/mbox.c b/arch/arm/cpu/arm1176/bcm2835/mbox.c
new file mode 100644
index 0000000..fd65e33
--- /dev/null
+++ b/arch/arm/cpu/arm1176/bcm2835/mbox.c
@@ -0,0 +1,164 @@
+/*
+ * (C) Copyright 2012 Stephen Warren
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <common.h>
+#include <asm/io.h>
+#include <asm/arch/mbox.h>
+
+#define TIMEOUT (100 * 1000) /* 100mS in uS */
+
+int bcm2835_mbox_call_raw(u32 chan, u32 send, u32 *recv)
+{
+	struct bcm2835_mbox_regs *regs =
+		(struct bcm2835_mbox_regs *)BCM2835_MBOX_PHYSADDR;
+	ulong endtime = get_timer(0) + TIMEOUT;
+	u32 val;
+
+	debug("time: %lu timeout: %lu\n", get_timer(0), endtime);
+
+	if (send & BCM2835_CHAN_MASK) {
+		printf("mbox: Illegal mbox data 0x%08x\n", send);
+		return -1;
+	}
+
+	/* Drain any stale responses */
+
+	for (;;) {
+		val = readl(&regs->status);
+		if (val & BCM2835_MBOX_STATUS_RD_EMPTY)
+			break;
+		if (get_timer(0) >= endtime) {
+			printf("mbox: Timeout draining stale responses\n");
+			return -1;
+		}
+		val = readl(&regs->read);
+	}
+
+	/* Wait for space to send */
+
+	for (;;) {
+		val = readl(&regs->status);
+		if (!(val & BCM2835_MBOX_STATUS_WR_FULL))
+			break;
+		if (get_timer(0) >= endtime) {
+			printf("mbox: Timeout waiting for send space\n");
+			return -1;
+		}
+	}
+
+	/* Send the request */
+
+	val = BCM2835_MBOX_PACK(chan, send);
+	debug("mbox: TX raw: 0x%08x\n", val);
+	writel(val, &regs->write);
+
+	/* Wait for the response */
+
+	for (;;) {
+		val = readl(&regs->status);
+		if (!(val & BCM2835_MBOX_STATUS_RD_EMPTY))
+			break;
+		if (get_timer(0) >= endtime) {
+			printf("mbox: Timeout waiting for response\n");
+			return -1;
+		}
+	}
+
+	/* Read the response */
+
+	val = readl(&regs->read);
+	debug("mbox: RX raw: 0x%08x\n", val);
+
+	/* Validate the response */
+
+	if (BCM2835_MBOX_UNPACK_CHAN(val) != chan) {
+		printf("mbox: Response channel mismatch\n");
+		return -1;
+	}
+
+	*recv = BCM2835_MBOX_UNPACK_DATA(val);
+
+	return 0;
+}
+
+#ifdef DEBUG
+void dump_buf(struct bcm2835_mbox_hdr *buffer)
+{
+	u32 *p;
+	u32 words;
+	int i;
+
+	p = (u32 *)buffer;
+	words = buffer->buf_size / 4;
+	for (i = 0; i < words; i++)
+		printf("    0x%04x: 0x%08x\n", i * 4, p[i]);
+}
+#endif
+
+int bcm2835_mbox_call_prop(u32 chan, struct bcm2835_mbox_hdr *buffer)
+{
+	int ret;
+	u32 rbuffer;
+	struct bcm2835_mbox_tag_hdr *tag;
+	int tag_index;
+
+#ifdef DEBUG
+	printf("mbox: TX buffer\n");
+	dump_buf(buffer);
+#endif
+
+	ret = bcm2835_mbox_call_raw(chan, (u32)buffer, &rbuffer);
+	if (ret)
+		return ret;
+	if (rbuffer != (u32)buffer) {
+		printf("mbox: Response buffer mismatch\n");
+		return -1;
+	}
+
+#ifdef DEBUG
+	printf("mbox: RX buffer\n");
+	dump_buf(buffer);
+#endif
+
+	/* Validate overall response status */
+
+	if (buffer->code != BCM2835_MBOX_RESP_CODE_SUCCESS) {
+		printf("mbox: Header response code invalid\n");
+		return -1;
+	}
+
+	/* Validate each tag's response status */
+
+	tag = (void *)(buffer + 1);
+	tag_index = 0;
+	while (tag->tag) {
+		if (!(tag->val_len & BCM2835_MBOX_TAG_VAL_LEN_RESPONSE)) {
+			printf("mbox: Tag %d missing val_len response bit\n",
+				tag_index);
+			return -1;
+		}
+		/*
+		 * Clear the reponse bit so clients can just look right at the
+		 * length field without extra processing
+		 */
+		tag->val_len &= ~BCM2835_MBOX_TAG_VAL_LEN_RESPONSE;
+		tag = (void *)(((u8 *)tag) + sizeof(*tag) + tag->val_buf_size);
+		tag_index++;
+	}
+
+	return 0;
+}