From: Paul Brook <paul@codesourcery.com>
To: John Williams <john.williams@petalogix.com>
Cc: "Peter A. G. Crosthwaite" <peter.crosthwaite@petalogix.com>,
edgar.iglesias@gmail.com, stefanha@gmail.com,
qemu-devel@nongnu.org, peter.maydell@linaro.org
Subject: Re: [Qemu-devel] [PATCH V4 0/5] Ehnahced SSI bus support + M25P80 SPI flash + Xilinx SPI controller
Date: Wed, 6 Jun 2012 14:18:52 +0100 [thread overview]
Message-ID: <201206061418.53159.paul@codesourcery.com> (raw)
In-Reply-To: <CACPZLaX5WN3Z6FtmiruYG5tQ1pmG1gCAUv5a3H+hb3S+MkCfCg@mail.gmail.com>
> On 5th April, when we first RFC'd our SPI layer support, you said to Peter:
>
> ==
> I don't believe there is any difference between SSI and SPI. It's the
> exact same thing - the same way that many devices support a "two-wire
> interface" that is actually just I2C with a different name.
>
> The behavior of the CS pin varies between devices. It sounds like you need
> a bit of extra logic not present in the current ssi code. You should fix
> that, not invent a whole new bus.
> ==
>
> He's gone and done exactly that, indeed generalised it with the
> proposed changes to SSI.
No. There are two changes. Modelling the CS line in the SPI bus, and having
SSI be a multipoint bus rather than point-point.
Paul
prev parent reply other threads:[~2012-06-06 13:19 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-04 8:08 [Qemu-devel] [PATCH V4 0/5] Ehnahced SSI bus support + M25P80 SPI flash + Xilinx SPI controller Peter A. G. Crosthwaite
2012-06-04 8:08 ` [Qemu-devel] [PATCH V4 1/5] SSI: Built in multiple device support Peter A. G. Crosthwaite
2012-06-04 8:08 ` [Qemu-devel] [PATCH V4 2/5] m25p80: initial verion Peter A. G. Crosthwaite
2012-06-04 8:08 ` [Qemu-devel] [PATCH V4 3/5] xilinx_spi: initial version Peter A. G. Crosthwaite
2012-06-04 8:08 ` [Qemu-devel] [PATCH V4 4/5] petalogix-ml605: added spi controller with m25p80 Peter A. G. Crosthwaite
2012-06-04 8:08 ` [Qemu-devel] [PATCH V4 5/5] stellaris: Updated spi bus implementation Peter A. G. Crosthwaite
2012-06-04 8:14 ` Peter Crosthwaite
2012-06-05 1:34 ` [Qemu-devel] [PATCH V4 0/5] Ehnahced SSI bus support + M25P80 SPI flash + Xilinx SPI controller Paul Brook
2012-06-05 1:54 ` Peter Crosthwaite
2012-06-06 13:37 ` Paul Brook
2012-06-05 2:51 ` John Williams
2012-06-06 13:18 ` Paul Brook [this message]
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