netdev - Re: [PATCH v2] r8169: default to 64-bit DMA on recent PCIe chips

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Message-ID: <20160516231128.GA21608@electric-eye.fr.zoreil.com>
Date:	Tue, 17 May 2016 01:11:28 +0200
From:	Francois Romieu <romieu@...zoreil.com>
To:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:	netdev@...r.kernel.org, ricardo.salveti@...aro.org,
	leif.lindholm@...aro.org, graeme.gregory@...aro.org,
	amit.kucheria@...aro.org, davem@...emloft.net,
	Realtek linux nic maintainers <nic_swsd@...ltek.com>
Subject: Re: [PATCH v2] r8169: default to 64-bit DMA on recent PCIe chips

Ard Biesheuvel <ard.biesheuvel@...aro.org> :
[...]
> This is a followup to 'r8169: default to 64-bit DMA on systems without memory
> below 4 GB' [1]. At the request of Francois, this version bases the decision
> whether to use 64-bit DMA by default on whether the device is PCIe and
> sufficiently recent, rather than whether the platform requires 64-bit DMA
> because it does not have any memory below 4 GB to begin with. This is safer,
> since it will prevent the use of such problematic cards on these platforms.

Testing has not been conclusive. It apparently works but I have not been
able to set addresses above 4Gb for the Rx or Tx descriptor rings yet.

-- 
Ueimor