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>

3 files changed, 572 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;
+}
diff --git a/arch/arm/include/asm/arch-bcm2835/mbox.h b/arch/arm/include/asm/arch-bcm2835/mbox.h
new file mode 100644
index 0000000..4752091
--- /dev/null
+++ b/arch/arm/include/asm/arch-bcm2835/mbox.h
@@ -0,0 +1,407 @@
+/*
+ * (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.
+ */
+
+#ifndef _BCM2835_MBOX_H
+#define _BCM2835_MBOX_H
+
+#include <linux/compiler.h>
+
+/*
+ * 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.
+ *
+ * The mailbox hardware supports passing 32-bit values back and forth.
+ * Presumably by software convention of the firmware, the bottom 4 bits of the
+ * value are used to indicate a logical channel, and the upper 28 bits are the
+ * actual payload. Various channels exist using these simple raw messages. See
+ * https://github.com/raspberrypi/firmware/wiki/Mailboxes for a list. As an
+ * example, the messages on the power management channel are a bitmask of
+ * devices whose power should be enabled.
+ *
+ * The property mailbox channel passes messages that contain the (16-byte
+ * aligned) ARM physical address of a memory buffer. This buffer is passed to
+ * the VC for processing, is modified in-place by the VC, and the address then
+ * passed back to the ARM CPU as the response mailbox message to indicate
+ * request completion. The buffers have a generic and extensible format; each
+ * buffer contains a standard header, a list of "tags", and a terminating zero
+ * entry. Each tag contains an ID indicating its type, and length fields for
+ * generic parsing. With some limitations, an arbitrary set of tags may be
+ * combined together into a single message buffer. This file defines structs
+ * representing the header and many individual tag layouts and IDs.
+ */
+
+/* Raw mailbox HW */
+
+#define BCM2835_MBOX_PHYSADDR	0x2000b880
+
+struct bcm2835_mbox_regs {
+	u32 read;
+	u32 rsvd0[5];
+	u32 status;
+	u32 config;
+	u32 write;
+};
+
+#define BCM2835_MBOX_STATUS_WR_FULL	0x80000000
+#define BCM2835_MBOX_STATUS_RD_EMPTY	0x40000000
+
+/* Lower 4-bits are channel ID */
+#define BCM2835_CHAN_MASK		0xf
+#define BCM2835_MBOX_PACK(chan, data)	(((data) & (~BCM2835_CHAN_MASK)) | \
+					 (chan & BCM2835_CHAN_MASK))
+#define BCM2835_MBOX_UNPACK_CHAN(val)	((val) & BCM2835_CHAN_MASK)
+#define BCM2835_MBOX_UNPACK_DATA(val)	((val) & (~BCM2835_CHAN_MASK))
+
+/* Property mailbox buffer structures */
+
+#define BCM2835_MBOX_PROP_CHAN		8
+
+/* All message buffers must start with this header */
+struct bcm2835_mbox_hdr {
+	u32 buf_size;
+	u32 code;
+};
+
+#define BCM2835_MBOX_REQ_CODE		0
+#define BCM2835_MBOX_RESP_CODE_SUCCESS	0x80000000
+
+#define BCM2835_MBOX_INIT_HDR(_m_) { \
+		memset((_m_), 0, sizeof(*(_m_))); \
+		(_m_)->hdr.buf_size = sizeof(*(_m_)); \
+		(_m_)->hdr.code = 0; \
+		(_m_)->end_tag = 0; \
+	}
+
+/*
+ * A message buffer contains a list of tags. Each tag must also start with
+ * a standardized header.
+ */
+struct bcm2835_mbox_tag_hdr {
+	u32 tag;
+	u32 val_buf_size;
+	u32 val_len;
+};
+
+#define BCM2835_MBOX_INIT_TAG(_t_, _id_) { \
+		(_t_)->tag_hdr.tag = BCM2835_MBOX_TAG_##_id_; \
+		(_t_)->tag_hdr.val_buf_size = sizeof((_t_)->body); \
+		(_t_)->tag_hdr.val_len = sizeof((_t_)->body.req); \
+	}
+
+#define BCM2835_MBOX_INIT_TAG_NO_REQ(_t_, _id_) { \
+		(_t_)->tag_hdr.tag = BCM2835_MBOX_TAG_##_id_; \
+		(_t_)->tag_hdr.val_buf_size = sizeof((_t_)->body); \
+		(_t_)->tag_hdr.val_len = 0; \
+	}
+
+/* When responding, the VC sets this bit in val_len to indicate a response */
+#define BCM2835_MBOX_TAG_VAL_LEN_RESPONSE	0x80000000
+
+/*
+ * Below we define the ID and struct for many possible tags. This header only
+ * defines individual tag structs, not entire message structs, since in
+ * general an arbitrary set of tags may be combined into a single message.
+ * Clients of the mbox API are expected to define their own overall message
+ * structures by combining the header, a set of tags, and a terminating
+ * entry. For example,
+ *
+ * struct msg {
+ *     struct bcm2835_mbox_hdr hdr;
+ *     struct bcm2835_mbox_tag_get_arm_mem get_arm_mem;
+ *     ... perhaps other tags here ...
+ *     u32 end_tag;
+ * };
+ */
+
+#define BCM2835_MBOX_TAG_GET_ARM_MEMORY		0x00010005
+
+struct bcm2835_mbox_tag_get_arm_mem {
+	struct bcm2835_mbox_tag_hdr tag_hdr;
+	union {
+		struct {
+		} req;
+		struct {
+			u32 mem_base;
+			u32 mem_size;
+		} resp;
+	} body;
+};
+
+#define BCM2835_MBOX_TAG_ALLOCATE_BUFFER	0x00040001
+
+struct bcm2835_mbox_tag_allocate_buffer {
+	struct bcm2835_mbox_tag_hdr tag_hdr;
+	union {
+		struct {
+			u32 alignment;
+		} req;
+		struct {
+			u32 fb_address;
+			u32 fb_size;
+		} resp;
+	} body;
+};
+
+#define BCM2835_MBOX_TAG_RELEASE_BUFFER		0x00048001
+
+struct bcm2835_mbox_tag_release_buffer {
+	struct bcm2835_mbox_tag_hdr tag_hdr;
+	union {
+		struct {
+		} req;
+		struct {
+		} resp;
+	} body;
+};
+
+#define BCM2835_MBOX_TAG_BLANK_SCREEN		0x00040002
+
+struct bcm2835_mbox_tag_blank_screen {
+	struct bcm2835_mbox_tag_hdr tag_hdr;
+	union {
+		struct {
+			/* bit 0 means on, other bots reserved */
+			u32 state;
+		} req;
+		struct {
+			u32 state;
+		} resp;
+	} body;
+};
+
+/* Physical means output signal */
+#define BCM2835_MBOX_TAG_GET_PHYSICAL_W_H	0x00040003
+#define BCM2835_MBOX_TAG_TEST_PHYSICAL_W_H	0x00044003
+#define BCM2835_MBOX_TAG_SET_PHYSICAL_W_H	0x00048003
+
+struct bcm2835_mbox_tag_physical_w_h {
+	struct bcm2835_mbox_tag_hdr tag_hdr;
+	union {
+		/* req not used for get */
+		struct {
+			u32 width;
+			u32 height;
+		} req;
+		struct {
+			u32 width;
+			u32 height;
+		} resp;
+	} body;
+};
+
+/* Virtual means display buffer */
+#define BCM2835_MBOX_TAG_GET_VIRTUAL_W_H	0x00040004
+#define BCM2835_MBOX_TAG_TEST_VIRTUAL_W_H	0x00044004
+#define BCM2835_MBOX_TAG_SET_VIRTUAL_W_H	0x00048004
+
+struct bcm2835_mbox_tag_virtual_w_h {
+	struct bcm2835_mbox_tag_hdr tag_hdr;
+	union {
+		/* req not used for get */
+		struct {
+			u32 width;
+			u32 height;
+		} req;
+		struct {
+			u32 width;
+			u32 height;
+		} resp;
+	} body;
+};
+
+#define BCM2835_MBOX_TAG_GET_DEPTH		0x00040005
+#define BCM2835_MBOX_TAG_TEST_DEPTH		0x00044005
+#define BCM2835_MBOX_TAG_SET_DEPTH		0x00048005
+
+struct bcm2835_mbox_tag_depth {
+	struct bcm2835_mbox_tag_hdr tag_hdr;
+	union {
+		/* req not used for get */
+		struct {
+			u32 bpp;
+		} req;
+		struct {
+			u32 bpp;
+		} resp;
+	} body;
+};
+
+#define BCM2835_MBOX_TAG_GET_PIXEL_ORDER	0x00040006
+#define BCM2835_MBOX_TAG_TEST_PIXEL_ORDER	0x00044005
+#define BCM2835_MBOX_TAG_SET_PIXEL_ORDER	0x00048006
+
+#define BCM2835_MBOX_PIXEL_ORDER_BGR		0
+#define BCM2835_MBOX_PIXEL_ORDER_RGB		1
+
+struct bcm2835_mbox_tag_pixel_order {
+	struct bcm2835_mbox_tag_hdr tag_hdr;
+	union {
+		/* req not used for get */
+		struct {
+			u32 order;
+		} req;
+		struct {
+			u32 order;
+		} resp;
+	} body;
+};
+
+#define BCM2835_MBOX_TAG_GET_ALPHA_MODE		0x00040007
+#define BCM2835_MBOX_TAG_TEST_ALPHA_MODE	0x00044007
+#define BCM2835_MBOX_TAG_SET_ALPHA_MODE		0x00048007
+
+#define BCM2835_MBOX_ALPHA_MODE_0_OPAQUE	0
+#define BCM2835_MBOX_ALPHA_MODE_0_TRANSPARENT	1
+#define BCM2835_MBOX_ALPHA_MODE_IGNORED		2
+
+struct bcm2835_mbox_tag_alpha_mode {
+	struct bcm2835_mbox_tag_hdr tag_hdr;
+	union {
+		/* req not used for get */
+		struct {
+			u32 alpha;
+		} req;
+		struct {
+			u32 alpha;
+		} resp;
+	} body;
+};
+
+#define BCM2835_MBOX_TAG_GET_PITCH		0x00040008
+
+struct bcm2835_mbox_tag_pitch {
+	struct bcm2835_mbox_tag_hdr tag_hdr;
+	union {
+		struct {
+		} req;
+		struct {
+			u32 pitch;
+		} resp;
+	} body;
+};
+
+/* Offset of display window within buffer */
+#define BCM2835_MBOX_TAG_GET_VIRTUAL_OFFSET	0x00040009
+#define BCM2835_MBOX_TAG_TEST_VIRTUAL_OFFSET	0x00044009
+#define BCM2835_MBOX_TAG_SET_VIRTUAL_OFFSET	0x00048009
+
+struct bcm2835_mbox_tag_virtual_offset {
+	struct bcm2835_mbox_tag_hdr tag_hdr;
+	union {
+		/* req not used for get */
+		struct {
+			u32 x;
+			u32 y;
+		} req;
+		struct {
+			u32 x;
+			u32 y;
+		} resp;
+	} body;
+};
+
+#define BCM2835_MBOX_TAG_GET_OVERSCAN		0x0004000a
+#define BCM2835_MBOX_TAG_TEST_OVERSCAN		0x0004400a
+#define BCM2835_MBOX_TAG_SET_OVERSCAN		0x0004800a
+
+struct bcm2835_mbox_tag_overscan {
+	struct bcm2835_mbox_tag_hdr tag_hdr;
+	union {
+		/* req not used for get */
+		struct {
+			u32 top;
+			u32 bottom;
+			u32 left;
+			u32 right;
+		} req;
+		struct {
+			u32 top;
+			u32 bottom;
+			u32 left;
+		} resp;
+	} body;
+};
+
+#define BCM2835_MBOX_TAG_GET_PALETTE		0x0004000b
+
+struct bcm2835_mbox_tag_get_palette {
+	struct bcm2835_mbox_tag_hdr tag_hdr;
+	union {
+		struct {
+		} req;
+		struct {
+			u32 data[1024];
+		} resp;
+	} body;
+};
+
+#define BCM2835_MBOX_TAG_TEST_PALETTE		0x0004400b
+
+struct bcm2835_mbox_tag_test_palette {
+	struct bcm2835_mbox_tag_hdr tag_hdr;
+	union {
+		struct {
+			u32 offset;
+			u32 num_entries;
+			u32 data[256];
+		} req;
+		struct {
+			u32 is_invalid;
+		} resp;
+	} body;
+};
+
+#define BCM2835_MBOX_TAG_SET_PALETTE		0x0004800b
+
+struct bcm2835_mbox_tag_set_palette {
+	struct bcm2835_mbox_tag_hdr tag_hdr;
+	union {
+		struct {
+			u32 offset;
+			u32 num_entries;
+			u32 data[256];
+		} req;
+		struct {
+			u32 is_invalid;
+		} resp;
+	} body;
+};
+
+/*
+ * Pass a raw u32 message to the VC, and receive a raw u32 back.
+ *
+ * Returns 0 for success, any other value for error.
+ */
+int bcm2835_mbox_call_raw(u32 chan, u32 send, u32 *recv);
+
+/*
+ * Pass a complete property-style buffer to the VC, and wait until it has
+ * been processed.
+ *
+ * This function expects a pointer to the mbox_hdr structure in an attempt
+ * to ensure some degree of type safety. However, some number of tags and
+ * a termination value are expected to immediately follow the header in
+ * memory, as required by the property protocol.
+ *
+ * Returns 0 for success, any other value for error.
+ */
+int bcm2835_mbox_call_prop(u32 chan, struct bcm2835_mbox_hdr *buffer);
+
+#endif