[PATCH] drm/i915/dp: Fix I2C/EDID handling with active DisplayPort to DVI converter

Chris Wilson chris at chris-wilson.co.uk
Wed Dec 8 12:17:12 PST 2010

On Wed, 8 Dec 2010 16:10:21 +0000, David Flynn <davidf at rd.bbc.co.uk> wrote:
> The DisplayPort standard (1.1a) states that:
>   The I2C-over-AUX Reply field is valid only when Native AUX CH Reply
>   field is AUX_ACK (00). When Native AUX CH Reply field is not 00, then,
>   I2C-over-AUX Reply field must be 00 and be ignored.
> This fixes broken EDID reading when using an active DisplayPort to
> duallink DVI converter.  If the AUX CH replier chooses to defer the
> transaction, a short read occurs and erroneous data is returned as
> the i2c reply due to a lack of length checking and failure to check
> for AUX ACK.

And it didn't break my bog standard DP setup. :)
Applied to -fixes and tagged for stable.


Chris Wilson, Intel Open Source Technology Centre

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