Re: [PATCH 4/6] arm64/io: Provide a WC friendly __iowriteXX_copy()

From: Catalin Marinas <catalin.marinas@arm.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Christian Borntraeger <borntraeger@linux.ibm.com>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Heiko Carstens <hca@linux.ibm.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Justin Stitt <justinstitt@google.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Leon Romanovsky <leon@kernel.org>,
	linux-rdma@vger.kernel.org, linux-s390@vger.kernel.org,
	llvm@lists.linux.dev, Ingo Molnar <mingo@redhat.com>,
	Bill Wendling <morbo@google.com>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	netdev@vger.kernel.org, Paolo Abeni <pabeni@redhat.com>,
	Salil Mehta <salil.mehta@huawei.com>,
	Jijie Shao <shaojijie@huawei.com>,
	Sven Schnelle <svens@linux.ibm.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	x86@kernel.org, Yisen Zhuang <yisen.zhuang@huawei.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Leon Romanovsky <leonro@mellanox.com>,
	linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	Mark Rutland <mark.rutland@arm.com>,
	Michael Guralnik <michaelgur@mellanox.com>,
	patches@lists.linux.dev, Niklas Schnelle <schnelle@linux.ibm.com>,
	Will Deacon <will@kernel.org>
Subject: Re: [PATCH 4/6] arm64/io: Provide a WC friendly __iowriteXX_copy()
Date: Thu, 29 Feb 2024 10:33:04 +0000	[thread overview]
Message-ID: <ZeBdYCa5Kxqas4O8@arm.com> (raw)
In-Reply-To: <4-v1-38290193eace+5-mlx5_arm_wc_jgg@nvidia.com>

On Tue, Feb 20, 2024 at 09:17:08PM -0400, Jason Gunthorpe wrote:
> +						 const u32 *from, size_t count)
> +{
> +	switch (count) {
> +	case 8:
> +		asm volatile("str %w0, [%8, #4 * 0]\n"
> +			     "str %w1, [%8, #4 * 1]\n"
> +			     "str %w2, [%8, #4 * 2]\n"
> +			     "str %w3, [%8, #4 * 3]\n"
> +			     "str %w4, [%8, #4 * 4]\n"
> +			     "str %w5, [%8, #4 * 5]\n"
> +			     "str %w6, [%8, #4 * 6]\n"
> +			     "str %w7, [%8, #4 * 7]\n"
> +			     :
> +			     : "rZ"(from[0]), "rZ"(from[1]), "rZ"(from[2]),
> +			       "rZ"(from[3]), "rZ"(from[4]), "rZ"(from[5]),
> +			       "rZ"(from[6]), "rZ"(from[7]), "r"(to));
> +		break;

BTW, talking of maintenance, would a series of __raw_writel() with
Mark's recent patch for offset addressing generate similar code? I.e.:

		__raw_writel(from[0], to);
		__raw_writel(from[1], to + 1);
		...
		__raw_writel(from[7], to + 7);

(you may have mentioned it in previous threads, I did not check)

-- 
Catalin