Re: [RFC PATCH 1/2] RISC-V: Mark existing SBI as legacy SBI.

From: Christoph Hellwig <hch@infradead.org>
To: Atish Patra <atish.patra@wdc.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>,
	Alan Kao <alankao@andestech.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Anup Patel <anup@brainfault.org>,
	Palmer Dabbelt <palmer@sifive.com>,
	linux-kernel@vger.kernel.org, Mike Rapoport <rppt@linux.ibm.com>,
	Alexios Zavras <alexios.zavras@intel.com>,
	Gary Guo <gary@garyguo.net>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	linux-riscv@lists.infradead.org,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [RFC PATCH 1/2] RISC-V: Mark existing SBI as legacy SBI.
Date: Tue, 27 Aug 2019 07:03:04 -0700	[thread overview]
Message-ID: <20190827140304.GA21855@infradead.org> (raw)
In-Reply-To: <20190826233256.32383-2-atish.patra@wdc.com>

> +#define SBI_EXT_LEGACY_SET_TIMER 0x0
> +#define SBI_EXT_LEGACY_CONSOLE_PUTCHAR 0x1
> +#define SBI_EXT_LEGACY_CONSOLE_GETCHAR 0x2
> +#define SBI_EXT_LEGACY_CLEAR_IPI 0x3
> +#define SBI_EXT_LEGACY_SEND_IPI 0x4
> +#define SBI_EXT_LEGACY_REMOTE_FENCE_I 0x5
> +#define SBI_EXT_LEGACY_REMOTE_SFENCE_VMA 0x6
> +#define SBI_EXT_LEGACY_REMOTE_SFENCE_VMA_ASID 0x7
> +#define SBI_EXT_LEGACY_SHUTDOWN 0x8

As Mike said legacy is a bit of a weird name.  I think this should
be SBI01_* or so.  And pleae align the numeric values and maybe use
an enum.

> +
> +#define SBI_CALL_LEGACY(which, arg0, arg1, arg2, arg3) ({             \
>  	register uintptr_t a0 asm ("a0") = (uintptr_t)(arg0);	\
>  	register uintptr_t a1 asm ("a1") = (uintptr_t)(arg1);	\
>  	register uintptr_t a2 asm ("a2") = (uintptr_t)(arg2);	\

Instead of the weird inline assembly with forced register allocation,
why not move this to pure assembly?  AFAICs this is the whole assembly
code we'd need:

ENTRY(sbi01_call)
        ecall
END(sbi01_call)

>  /* Lazy implementations until SBI is finalized */
> -#define SBI_CALL_0(which) SBI_CALL(which, 0, 0, 0, 0)
> -#define SBI_CALL_1(which, arg0) SBI_CALL(which, arg0, 0, 0, 0)
> -#define SBI_CALL_2(which, arg0, arg1) SBI_CALL(which, arg0, arg1, 0, 0)
> -#define SBI_CALL_3(which, arg0, arg1, arg2) \
> -		SBI_CALL(which, arg0, arg1, arg2, 0)
> -#define SBI_CALL_4(which, arg0, arg1, arg2, arg3) \
> -		SBI_CALL(which, arg0, arg1, arg2, arg3)
> +#define SBI_CALL_LEGACY_0(which) SBI_CALL_LEGACY(which, 0, 0, 0, 0)
> +#define SBI_CALL_LEGACY_1(which, arg0) SBI_CALL_LEGACY(which, arg0, 0, 0, 0)
> +#define SBI_CALL_LEGACY_2(which, arg0, arg1) \
> +		SBI_CALL_LEGACY(which, arg0, arg1, 0, 0)
> +#define SBI_CALL_LEGACY_3(which, arg0, arg1, arg2) \
> +		SBI_CALL_LEGACY(which, arg0, arg1, arg2, 0)
> +#define SBI_CALL_LEGACY_4(which, arg0, arg1, arg2, arg3) \
> +		SBI_CALL_LEGACY(which, arg0, arg1, arg2, arg3)

When you touch this anyway I'd suggest you kill these rather
pointless wrappers as well as the comment above them.

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