From: Andrew Lunn <andrew@lunn.ch>
To: Jakub Kicinski <jakub.kicinski@netronome.com>
Cc: netdev@vger.kernel.org, Esben Haabendal <esben@geanix.com>,
YueHaibing <yuehaibing@huawei.com>,
Michal Simek <michal.simek@xilinx.com>,
linux-kernel@vger.kernel.org, Yang Wei <yang.wei9@zte.com.cn>,
Luis Chamberlain <mcgrof@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 03/12] net: ll_temac: Fix support for 64-bit platforms
Date: Sat, 27 Apr 2019 00:02:26 +0200 [thread overview]
Message-ID: <20190426220226.GW4041@lunn.ch> (raw)
In-Reply-To: <20190426140856.78b786ee@cakuba.netronome.com>
On Fri, Apr 26, 2019 at 02:08:56PM -0700, Jakub Kicinski wrote:
> On Fri, 26 Apr 2019 22:59:12 +0200, Andrew Lunn wrote:
> > On Fri, Apr 26, 2019 at 11:40:13AM -0700, Jakub Kicinski wrote:
> > > On Fri, 26 Apr 2019 09:32:22 +0200, Esben Haabendal wrote:
> > > > The use of buffer descriptor APP4 field (32-bit) for storing skb pointer
> > > > obviously does not work on 64-bit platforms.
> > > > As APP3 is also unused, we can use that to store the other half of 64-bit
> > > > pointer values.
> > > >
> > > > Contrary to what is hinted at in commit message of commit 15bfe05c8d63
> > > > ("net: ethernet: xilinx: Mark XILINX_LL_TEMAC broken on 64-bit")
> > > > there are no other pointers stored in cdmac_bd.
> > > >
> > > > Signed-off-by: Esben Haabendal <esben@geanix.com>
> > >
> > > This is a bit strange, the driver stores the host's virtual address into
> > > the HW descriptor?
Lets try that again
Hi Jakub
> > Hi Jukub
>
> I need to start keeping track of all the ways my name gets spelled :)
> I find it entertaining :)
Sorry.
And i prefer entertaining over offended :-)
> > This is reasonably common. You need some sort of cookie which links
> > the hardware descriptor to the skbuf it points to. The hardware makes
> > no use of it, it is just a cookie.
>
> Right, but accesses to HW descriptor memory ring are significantly
> more expensive, especially on platforms which are not coherent with
> DMA operations (everything but x86?)
>
> A preferable design is to have two descriptor rings - one for HW
> descriptors and one for software context, no?
Modern drivers do that. But this driver seems to be quite old. And if
you look at what it is used on, PPC & MICROBLAZE, they are old
architectures, i don't think hardware access are that as expensive as
for modern architectures.
Andrew
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next prev parent reply other threads:[~2019-04-26 22:02 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190426073231.4008-1-esben@geanix.com>
[not found] ` <20190426073231.4008-3-esben@geanix.com>
2019-04-26 13:58 ` [PATCH 02/12] net: ll_temac: Extend support to non-device-tree platforms Andrew Lunn
[not found] ` <20190426073231.4008-11-esben@geanix.com>
2019-04-26 14:01 ` [PATCH 10/12] net: ll_temac: Replace bad usage of msleep() with usleep_range() Andrew Lunn
[not found] ` <20190426073231.4008-7-esben@geanix.com>
2019-04-26 14:05 ` [PATCH 06/12] net: ll_temac: Allow use on x86 platforms Andrew Lunn
[not found] ` <20190426073231.4008-8-esben@geanix.com>
2019-04-26 14:14 ` [PATCH 07/12] net: ll_temac: Support indirect_mutex share within TEMAC IP Andrew Lunn
[not found] ` <20190426073231.4008-9-esben@geanix.com>
2019-04-26 14:21 ` [PATCH 08/12] net: ll_temac: Fix iommu/swiotlb leak Andrew Lunn
2019-04-26 14:43 ` Robin Murphy
2019-04-26 15:37 ` Andrew Lunn
[not found] ` <20190426073231.4008-4-esben@geanix.com>
2019-04-26 18:40 ` [PATCH 03/12] net: ll_temac: Fix support for 64-bit platforms Jakub Kicinski
2019-04-26 20:59 ` Andrew Lunn
2019-04-26 21:08 ` Jakub Kicinski
2019-04-26 22:02 ` Andrew Lunn [this message]
2019-04-26 22:30 ` Jakub Kicinski
[not found] ` <20190429083422.4356-1-esben@geanix.com>
[not found] ` <20190429083422.4356-4-esben@geanix.com>
2019-04-29 22:06 ` Andrew Lunn
[not found] ` <20190429083422.4356-7-esben@geanix.com>
2019-04-29 22:06 ` [PATCH 06/12] net: ll_temac: Allow use on x86 platforms Andrew Lunn
[not found] ` <20190429083422.4356-8-esben@geanix.com>
2019-04-29 22:12 ` [PATCH 07/12] net: ll_temac: Support indirect_mutex share within TEMAC IP Andrew Lunn
[not found] ` <20190430071759.2481-1-esben@geanix.com>
[not found] ` <20190430071759.2481-8-esben@geanix.com>
2019-04-30 16:59 ` [PATCH v3 " Andrew Lunn
[not found] ` <20190430071759.2481-9-esben@geanix.com>
2019-04-30 17:00 ` [PATCH v3 08/12] net: ll_temac: Fix iommu/swiotlb leak Andrew Lunn
2019-05-01 18:33 ` [PATCH v3 00/12] net: ll_temac: x86_64 support David Miller
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