linux-kernel - Re: [PATCH v4 2/7] MIPS: Loongson64: Distinguish firmware dependencies DTB/LEFI

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Message-ID: <2484af69-13d1-09ff-3785-6c89cac4ffbd@rempel-privat.de>
Date:   Wed, 10 Mar 2021 11:57:23 +0100
From:   Oleksij Rempel <linux@...pel-privat.de>
To:     Qing Zhang <zhangqing@...ngson.cn>,
        Huacai Chen <chenhuacai@...nel.org>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>
Cc:     linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, Ming Wang <wangming01@...ngson.cn>
Subject: Re: [PATCH v4 2/7] MIPS: Loongson64: Distinguish firmware
 dependencies DTB/LEFI

Hi,

Am 10.03.21 um 08:56 schrieb Qing Zhang:
> Add DTB boot support, only support Loongson-2K1000 processor
> for now, determine whether to use the built-in DTB or the DTB
> from the firmware by checking the range of CKSEG0 and XKPHYS.
> loongson_fw_interface will be used in the future.
>
> Signed-off-by: Jiaxun Yang <jiaxun.yang@...goat.com>
> Signed-off-by: Qing Zhang <zhangqing@...ngson.cn>
> Tested-by: Ming Wang <wangming01@...ngson.cn>
> ---
>
> v3-v4: Standard submission of information
>        Fix error handling
>
>  .../include/asm/mach-loongson64/boot_param.h     |  6 ++++++
>  arch/mips/include/asm/mach-loongson64/loongson.h |  3 ++-
>  arch/mips/loongson64/env.c                       | 13 ++++++++++++-
>  arch/mips/loongson64/init.c                      | 16 ++++++++++++++--
>  4 files changed, 34 insertions(+), 4 deletions(-)
>
> diff --git a/arch/mips/include/asm/mach-loongson64/boot_param.h b/arch/mips/include/asm/mach-loongson64/boot_param.h
> index 4592841b6b0c..43737401dc06 100644
> --- a/arch/mips/include/asm/mach-loongson64/boot_param.h
> +++ b/arch/mips/include/asm/mach-loongson64/boot_param.h
> @@ -198,7 +198,13 @@ enum loongson_bridge_type {
>  	VIRTUAL = 3
>  };
>
> +enum loongson_fw_interface {
> +	LOONGSON_LEFI,
> +	LOONGSON_DTB,
> +};
> +
>  struct loongson_system_configuration {
> +	enum loongson_fw_interface fw_interface;
>  	u32 nr_cpus;
>  	u32 nr_nodes;
>  	int cores_per_node;
> diff --git a/arch/mips/include/asm/mach-loongson64/loongson.h b/arch/mips/include/asm/mach-loongson64/loongson.h
> index ac1c20e172a2..3f885fa26ba6 100644
> --- a/arch/mips/include/asm/mach-loongson64/loongson.h
> +++ b/arch/mips/include/asm/mach-loongson64/loongson.h
> @@ -23,7 +23,8 @@ extern u32 memsize, highmemsize;
>  extern const struct plat_smp_ops loongson3_smp_ops;
>
>  /* loongson-specific command line, env and memory initialization */
> -extern void __init prom_init_env(void);
> +extern void __init prom_dtb_init_env(void);
> +extern void __init prom_lefi_init_env(void);
>  extern void __init szmem(unsigned int node);
>  extern void *loongson_fdt_blob;
>
> diff --git a/arch/mips/loongson64/env.c b/arch/mips/loongson64/env.c
> index 51a5d050a94c..e7d3a06175e3 100644
> --- a/arch/mips/loongson64/env.c
> +++ b/arch/mips/loongson64/env.c
> @@ -43,7 +43,18 @@ const char *get_system_type(void)
>  	return "Generic Loongson64 System";
>  }
>
> -void __init prom_init_env(void)
> +
> +void __init prom_dtb_init_env(void)
> +{
> +	if ((fw_arg2 < CKSEG0 || fw_arg2 > CKSEG1)
> +		&& (fw_arg2 < XKPHYS || fw_arg2 > XKSEG))
> +
> +		loongson_fdt_blob = __dtb_loongson64_2core_2k1000_begin;
> +	else
> +		loongson_fdt_blob = (void *)fw_arg2;
> +}
> +
> +void __init prom_lefi_init_env(void)
>  {
>  	struct boot_params *boot_p;
>  	struct loongson_params *loongson_p;
> diff --git a/arch/mips/loongson64/init.c b/arch/mips/loongson64/init.c
> index cfa788bca871..ed280b73bf89 100644
> --- a/arch/mips/loongson64/init.c
> +++ b/arch/mips/loongson64/init.c
> @@ -52,6 +52,10 @@ void __init szmem(unsigned int node)
>  	static unsigned long num_physpages;
>  	u64 node_id, node_psize, start_pfn, end_pfn, mem_start, mem_size;
>
> +	/* Otherwise come from DTB */
> +	if (loongson_sysconf.fw_interface != LOONGSON_LEFI)
> +		return;
> +
>  	/* Parse memory information and activate */
>  	for (i = 0; i < loongson_memmap->nr_map; i++) {
>  		node_id = loongson_memmap->map[i].node_id;
> @@ -94,12 +98,20 @@ static void __init prom_init_memory(void)
>  void __init prom_init(void)
>  {
>  	fw_init_cmdline();
> -	prom_init_env();
> +
> +	if (fw_arg2 == 0 || (fdt_magic(fw_arg2) == FDT_MAGIC)) {
> +		loongson_sysconf.fw_interface = LOONGSON_DTB;
> +		prom_dtb_init_env();
> +	} else {
> +		loongson_sysconf.fw_interface = LOONGSON_LEFI;
> +		prom_lefi_init_env();
> +	}

Is it possible to make it compatible with MIPS UHI boot protocol? So boot loaders will be able to
handle Loongson kernel images as any other MIPS kernel images?

This protocol is described here on page 15, "3. Boot protocols"
https://docplayer.net/62444141-Unified-hosting-interface-md01069-reference-manual.html

According to this protocol, you should have:
fw_arg0 = -2
fw_arg1 = Virtual (kseg0) address of Device Tree Blob

This would made LS a first grade resident for many boot loaders and save a lot of needles headaches.

--
Regards,
Oleksij