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    SubjectRe: [PATCH 4/8 v7] drm/i915/intel_i2c: use WAIT cycle, not STOP
    On Tue, Apr 10, 2012 at 12:37:46PM +0200, Daniel Vetter wrote:
    > On Fri, Mar 30, 2012 at 07:46:39PM +0800, Daniel Kurtz wrote:
    > > The i915 is only able to generate a STOP cycle (i.e. finalize an i2c
    > > transaction) during a DATA or WAIT phase. In other words, the
    > > controller rejects a STOP requested as part of the first transaction in a
    > > sequence.
    > >
    > > Thus, for the first transaction we must always use a WAIT cycle, detect
    > > when the device has finished (and is in a WAIT phase), and then either
    > > start the next transaction, or, if there are no more transactions,
    > > generate a STOP cycle.
    > >
    > > Note: Theoretically, the last transaction of a multi-transaction sequence
    > > could initiate a STOP cycle. However, this slight optimization is left
    > > for another patch. We return -ETIMEDOUT if the hardware doesn't
    > > deactivate after the STOP cycle.
    > >
    > > Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
    >
    > I've re-read gmbus register spec and STOP seems to be allowed even in the
    > first cycle. Does this patch solve an issue for you? If not, I prefer we
    > just drop it.

    Actually I'd like to keep the -ETIMEDOUT return value, so maybe we should
    keeep that hunk. I've picked up the previous 3 patches of this series, the
    once after this one here conflict (without this patch here).
    -Daniel
    --
    Daniel Vetter
    Mail: daniel@ffwll.ch
    Mobile: +41 (0)79 365 57 48


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