Re: [PATCH v2 05/22] ARM64: implement ioremap_nopost() interface

From: Will Deacon <will.deacon@arm.com>
To: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Wenrui Li <wenrui.li@rock-chips.com>,
	Gabriele Paoloni <gabriele.paoloni@huawei.com>,
	linux-pci@vger.kernel.org, Shawn Lin <shawn.lin@rock-chips.com>,
	Michal Simek <michal.simek@xilinx.com>,
	Thierry Reding <thierry.reding@gmail.com>,
	Tanmay Inamdar <tinamdar@apm.com>,
	Joao Pinto <Joao.Pinto@synopsys.com>,
	Pratyush Anand <pratyush.anand@gmail.com>,
	Russell King <linux@armlinux.org.uk>,
	Bharat Kumar Gogada <bharat.kumar.gogada@xilinx.com>,
	Murali Karicheri <m-karicheri2@ti.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Arnd Bergmann <arnd@arndb.de>, Jon Mason <jonmason@broadcom.com>,
	Ray Jui <rjui@broadcom.com>, John Garry <john.garry@huawei.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Mingkai Hu <mingkai.hu@freescale.com>,
	linux-arm-kernel@lists.infradead.org,
	"Luis R. Rodriguez" <mcgrof@kernel.org>,
	Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
	Jingoo Han <jingoohan1@gmail.com>,
	linux-kernel@vger.kernel.org,
	Stanimir Varbanov <svarbanov@mm-sol.com>,
	Minghuan Lian <minghuan.Lian@freescale.com>,
	Zhou Wang <wangzhou1@hisilicon.com>,
	Roy Zang <tie-fei.zang@freescale.com>
Subject: Re: [PATCH v2 05/22] ARM64: implement ioremap_nopost() interface
Date: Thu, 30 Mar 2017 17:19:31 +0100	[thread overview]
Message-ID: <20170330161931.GA5623@arm.com> (raw)
In-Reply-To: <20170327094954.7162-6-lorenzo.pieralisi@arm.com>

On Mon, Mar 27, 2017 at 10:49:33AM +0100, Lorenzo Pieralisi wrote:
> The PCI bus specifications (rev 3.0, 3.2.5 "Transaction Ordering
> and Posting") defines rules for PCI configuration space transactions
> ordering and posting, that state that configuration writes
> are non-posted transactions.
> 
> This rule is reinforced by the ARM v8 architecture reference manual
> (issue A.k, Early Write Acknowledgment) that explicitly recommends
> that No Early Write Acknowledgment attribute should be used to map
> PCI configuration (write) transactions.
> 
> Current ioremap interface on ARM64 implements mapping functions
> where the Early Write Acknowledgment hint is enabled, so they
> cannot be used to map PCI configuration space in a PCI specs
> compliant way.
> 
> Implement an ARM64 specific ioremap_nopost() interface
> that allows to map PCI config region with nGnRnE attributes, providing
> a remap function that complies with PCI specifications and the ARMv8
> architecture reference manual recommendations.
> 
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> ---
>  arch/arm64/include/asm/io.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)

Acked-by: Will Deacon <will.deacon@arm.com>

Let me know if you need this taken via the arm64 tree.

Will

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