[PATCH] RISC-V: virt: support poweroff/restart on tinyemu

[Sascha Hauer]

On Thu, Sep 16, 2021 at 11:35:32AM +0200, Ahmad Fatoum wrote:
> QEMU Virt on RISC-V has syscon-reboot and syscon-poweroff compatible
> devices and describes them in the device tree. TinyEMU's Virt machine
> is different and has a HTIF based poweroff and no dedicated reset
> mechanism. Add board support for the HTIF poweroff and use a poor man's
> reset that jumps back to the reset vector.
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
> ---
>  arch/riscv/Kconfig.socs             |  8 +++
>  arch/riscv/boards/Makefile          |  1 +
>  arch/riscv/boards/riscvemu/Makefile |  1 +
>  arch/riscv/boards/riscvemu/board.c  | 76 +++++++++++++++++++++++++++++
>  4 files changed, 86 insertions(+)
>  create mode 100644 arch/riscv/boards/riscvemu/Makefile
>  create mode 100644 arch/riscv/boards/riscvemu/board.c

Applied, thanks

Sascha

> 
> diff --git a/arch/riscv/Kconfig.socs b/arch/riscv/Kconfig.socs
> index 221ea133d4d0..1bd9b4d579d9 100644
> --- a/arch/riscv/Kconfig.socs
> +++ b/arch/riscv/Kconfig.socs
> @@ -22,6 +22,14 @@ config SOC_VIRT
>  	  Generates an image tht can be be booted by QEMU. The image is called
>  	  barebox-dt-2nd.img
>  
> +config BOARD_RISCVEMU
> +	depends on SOC_VIRT
> +	bool "TinyEMU Virt Machine (riscvemu)"
> +	default y
> +	help
> +	  TinyEMU's Virt machine differs from QEMU in poweroff and restart
> +	  mechanisms. This adds the necessary support.
> +
>  config CPU_SIFIVE
>  	bool
>  	select HAS_CACHE
> diff --git a/arch/riscv/boards/Makefile b/arch/riscv/boards/Makefile
> index cb28a25d8bc8..99630266d126 100644
> --- a/arch/riscv/boards/Makefile
> +++ b/arch/riscv/boards/Makefile
> @@ -2,3 +2,4 @@
>  obj-$(CONFIG_BOARD_ERIZO_GENERIC)	+= erizo/
>  obj-$(CONFIG_BOARD_HIFIVE)		+= hifive/
>  obj-$(CONFIG_BOARD_BEAGLEV)		+= beaglev/
> +obj-$(CONFIG_BOARD_RISCVEMU)		+= riscvemu/
> diff --git a/arch/riscv/boards/riscvemu/Makefile b/arch/riscv/boards/riscvemu/Makefile
> new file mode 100644
> index 000000000000..dcfc2937d325
> --- /dev/null
> +++ b/arch/riscv/boards/riscvemu/Makefile
> @@ -0,0 +1 @@
> +obj-y += board.o
> diff --git a/arch/riscv/boards/riscvemu/board.c b/arch/riscv/boards/riscvemu/board.c
> new file mode 100644
> index 000000000000..7dbf9afe4c2d
> --- /dev/null
> +++ b/arch/riscv/boards/riscvemu/board.c
> @@ -0,0 +1,76 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (C) 2021 Ahmad Fatoum, Pengutronix
> + */
> +
> +#include <common.h>
> +#include <driver.h>
> +#include <poweroff.h>
> +#include <restart.h>
> +#include <asm/system.h>
> +#include <asm/barebox-riscv.h>
> +
> +struct riscvemu_priv {
> +	struct restart_handler rst;
> +	void __noreturn (*restart)(unsigned long, void *);
> +
> +};
> +
> +#define HTIF_BASE_ADDR		IOMEM(0x40008000)
> +#define HTIF_TOHOST_LOW		(HTIF_BASE_ADDR + 0)
> +#define HTIF_TOHOST_HIGH	(HTIF_BASE_ADDR + 4)
> +
> +static void __noreturn riscvemu_poweroff(struct poweroff_handler *pwr)
> +{
> +	writel(1, HTIF_TOHOST_LOW);
> +	writel(0, HTIF_TOHOST_HIGH);
> +
> +	__builtin_unreachable();
> +}
> +
> +static void __noreturn riscvemu_restart(struct restart_handler *rst)
> +{
> +	struct riscvemu_priv *priv = container_of(rst, struct riscvemu_priv, rst);
> +
> +	/*
> +	 * barebox PBL relocates itself to end of RAM early on, so unless
> +	 * something explicitly scrubbed the initial PBL, we can jump back to
> +	 * the reset vector to "reset".
> +	 */
> +	priv->restart(riscv_hartid(), barebox_riscv_boot_dtb());
> +}
> +
> +static int riscvemu_probe(struct device_d *dev)
> +{
> +	struct device_node *of_chosen;
> +	struct riscvemu_priv *priv;
> +	u64 start;
> +
> +	if (of_find_compatible_node(NULL, NULL, "ucb,htif0"))
> +		poweroff_handler_register_fn(riscvemu_poweroff);
> +
> +	of_chosen = of_find_node_by_path("/chosen");
> +
> +	if (of_property_read_u64(of_chosen, "riscv,kernel-start", &start))
> +		return 0;
> +
> +	priv = xzalloc(sizeof(*priv));
> +
> +	priv->restart = (void *)(uintptr_t)start;
> +	priv->rst.restart = riscvemu_restart;
> +	priv->rst.name = "vector";
> +
> +	return restart_handler_register(&priv->rst);
> +}
> +
> +static const struct of_device_id riscvemu_of_match[] = {
> +	{ .compatible = "ucbbar,riscvemu-bar_dev" },
> +	{ /* sentinel */ },
> +};
> +
> +static struct driver_d riscvemu_board_driver = {
> +	.name = "board-riscvemu",
> +	.probe = riscvemu_probe,
> +	.of_compatible = riscvemu_of_match,
> +};
> +device_platform_driver(riscvemu_board_driver);
> -- 
> 2.30.2
> 
> 
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