[PATCH 1/2] ARM: bcm2835: add mailbox driver

[Albert ARIBAUD]

Hi Stephen,

On Mon, 15 Oct 2012 23:10:35 -0600, Stephen Warren
<swarren at wwwdotorg.org> wrote:

> 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 supports two forms
> of communication: Raw 28-bit values, and a so-called "property"
> interface, where the 28-bit value is a physical pointer to a memory
> buffer that contains various "tags".
> 
> 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 at wwwdotorg.org>
> ---
>  arch/arm/cpu/arm1176/bcm2835/Makefile    |    2 +-
>  arch/arm/cpu/arm1176/bcm2835/mbox.c      |   92 ++++++++++++++++++++++++++++++
>  arch/arm/include/asm/arch-bcm2835/mbox.h |   87 ++++++++++++++++++++++++++++
>  3 files changed, 180 insertions(+), 1 deletion(-)
>  create mode 100644 arch/arm/cpu/arm1176/bcm2835/mbox.c
>  create mode 100644 arch/arm/include/asm/arch-bcm2835/mbox.h
> 
> 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..f5c060b
> --- /dev/null
> +++ b/arch/arm/cpu/arm1176/bcm2835/mbox.c
> @@ -0,0 +1,92 @@
> +/*
> + * (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
> + * version 2 as published by the Free Software Foundation.
> + *
> + * 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;
> +
> +	if (send & BCM2835_CHAN_MASK)
> +		return -1;
> +
> +	/* Drain any stale responses */
> +
> +	for (;;) {
> +		val = readl(&regs->status);
> +		if (val & BCM2835_MBOX_STATUS_RD_EMPTY)
> +			break;
> +		if (get_timer(0) >= endtime)
> +			return -1;
> +		val = readl(&regs->read);
> +	}
> +
> +	/* Send the request */
> +
> +	/* FIXME: timeout */

Develop this FIXME to indicate what exactly should be fixed.

> +	for (;;) {
> +		val = readl(&regs->status);
> +		if (!(val & BCM2835_MBOX_STATUS_WR_FULL))
> +			break;
> +		if (get_timer(0) >= endtime)
> +			return -1;
> +	}
> +
> +	writel(BCM2835_MBOX_PACK(chan, send), &regs->write);
> +
> +	/* Wait for the response */
> +
> +	/* FIXME: timeout */

Ditto.

> +	for (;;) {
> +		val = readl(&regs->status);
> +		if (!(val & BCM2835_MBOX_STATUS_RD_EMPTY))
> +			break;
> +		if (get_timer(0) >= endtime)
> +			return -1;
> +	}
> +
> +	val = readl(&regs->read);
> +
> +	/* Validate the response */
> +
> +	if (BCM2835_MBOX_UNPACK_CHAN(val) != chan)
> +		return -1;
> +
> +	*recv = BCM2835_MBOX_UNPACK_DATA(val);
> +
> +	return 0;
> +}
> +
> +int bcm2835_mbox_call_prop(u32 chan, struct bcm2835_mbox_prop_hdr *buffer)
> +{
> +	int ret;
> +	u32 rbuffer;
> +
> +	ret = bcm2835_mbox_call_raw(chan, (u32)buffer, &rbuffer);
> +	if (ret)
> +		return ret;
> +	if (rbuffer != (u32)buffer)
> +		return -1;
> +
> +	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..907fabd
> --- /dev/null
> +++ b/arch/arm/include/asm/arch-bcm2835/mbox.h
> @@ -0,0 +1,87 @@
> +/*
> + * (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
> + * version 2 as published by the Free Software Foundation.
> + *
> + * 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>
> +
> +/* 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
> +
> +#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
> +
> +struct bcm2835_mbox_prop_hdr {
> +	u32 buf_size;
> +	u32 code;
> +} __packed;

Remove __packed here, as all fields are 32 bits and thus no padding
would happen anyway.

> +#define BCM2835_MBOX_REQ_CODE		0
> +#define BCM2835_MBOX_RESP_CODE_SUCCESS	0x80000000
> +
> +struct bcm2835_mbox_tag_hdr {
> +	u32 tag;
> +	u32 val_buf_size;
> +	u32 val_len;
> +} __packed;

Ditto.

> +#define BCM2835_MBOX_TAG_VAL_LEN_RESPONSE	0x80000000
> +
> +#define BCM2835_MBOX_TAG_GET_ARM_MEMORY		0x00010005
> +
> +struct bcm2835_mbox_req_get_arm_mem {
> +} __packed;

Ditto (for an empty struct).

> +struct bcm2835_mbox_resp_get_arm_mem {
> +	u32 mem_base;
> +	u32 mem_size;
> +} __packed;

Ditto.

> +struct bcm2835_mbox_buf_get_arm_mem {
> +	struct bcm2835_mbox_prop_hdr hdr;
> +	struct bcm2835_mbox_tag_hdr tag_hdr;
> +	union {
> +		struct bcm2835_mbox_req_get_arm_mem req;
> +		struct bcm2835_mbox_resp_get_arm_mem resp;
> +	} body;
> +	u32 end_tag;
> +} __packed;

Ditto.

Also, what is the point of bcm2835_mbox_buf_get_arm_mem which is not
referenced in the API below?

> +int bcm2835_mbox_call_raw(u32 chan, u32 send, u32 *recv);
> +int bcm2835_mbox_call_prop(u32 chan, struct bcm2835_mbox_prop_hdr *buffer);
> +
> +#endif

Amicalement,
-- 
Albert.