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    SubjectRe: [PATCH 03/12] net: ll_temac: Fix support for 64-bit platforms
    On Sat, 27 Apr 2019 00:02:26 +0200, Andrew Lunn wrote:
    > 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 :-)

    Certainly no offence taken! :)

    > > > 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.

    True, my comment was certainly more of a suggestion than a blocker.

    Looking closer at the series it kind of looks like a soft IP.
    Esben, is there anything architecture specific here? Should we perhaps
    drop the dependency on the architectures in patch 6 completely?

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