Re: [PATCH RFC v2 0/5] Link Training Compliance support, link rate fallback sending Uevent

[Jani Nikula <jani.nikula@linux.intel.com>]

On Sat, 08 Oct 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> This adds support in the kernel to handle link training compliance
> requests and send a uevent to train at requested parameters.
> In this patch series, if the link training fails in modeset, then a
> hotplug uevent is added to a work queue and scheduled and failed link
> parameters are stored in intel_dp structure. This uevent
> gets executed after the modeset is completed and after locks are released.
> In the modeset retry, modes are validated based on lower link rate from
> the failed link rate value to prune the modes in intel_dp_mode_valid().
> The lower link rate is then used toc onfigure the pipe and link is retrained
> at this lower link rate.
>
> I have tested this with DPR-120 and the compliance tests are passing.
> The DP CTS spec is based on DP 1.2 spec and it only expects to reduce the link
> rate and train at the max lane count without reducing the lane count. Lane count
> reduction is added in DP 1.3 so Unigraf has agreed to add it to their next SW release.
> Hence I have not implemented fallback for lane count. But I can add it if you think
> we should add DP 1.3 link training algorithm.
>
> Please let me know your feedback on this. Compliance app is not required for link training
> tests and so I have tested this fallback using kernel console mode on Source DUT.

The question is, can you pass the link training tests using a userspace
that responds to hotplug uevents? I think you mentioned a timeout in the
CTS. If you're using fbdev, I think the retry modeset may happen faster
than with a regular userspace.

BR,
Jani.


>
> v2:
> * Corect the order of patches for correct dependencies
>
> Manasi Navare (4):
>   drm/i915; Add a function to return index of link rate
>   drm/i915: Add support for DP link training compliance
>   drm/i915: Work queue for uevent
>   drm/i915: Link Rate fallback on Link training failure
>
> Navare, Manasi D (1):
>   drm/i915: Change the placement of some static functions in intel_dp.c
>
>  drivers/gpu/drm/i915/i915_drv.h               |   2 +
>  drivers/gpu/drm/i915/intel_ddi.c              |  10 +-
>  drivers/gpu/drm/i915/intel_dp.c               | 277 ++++++++++++++++++--------
>  drivers/gpu/drm/i915/intel_dp_link_training.c |  12 +-
>  drivers/gpu/drm/i915/intel_drv.h              |   8 +-
>  5 files changed, 217 insertions(+), 92 deletions(-)

-- 
Jani Nikula, Intel Open Source Technology Center
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