On Tue, Mar 15, 2016 at 01:38:58PM +0200, Mika Kahola wrote:
> Additional 50 ms delay is needed between DPCD reads on HP Bizlink 1326
> DP to VGA adapter. Having said that, I haven't noticed a need for
> additional delay between DPCD reads on other DP-VGA dongles.
>
> While at it, let's replace mdelay() with usleep_range() routine.
>
> Signed-off-by: Mika Kahola <mika.kahola@xxxxxxxxx>
Please don't add more hacks to our own private copy of read_wake. This
stuff needs to move into drm core, since really we can't be the only ones
who try to plug in shit dongles ;-)
Would be great to test this with an amd DP card and the exact same
connector and see what happens. Then move these read_wake hacks into the
drm_dp_dpcd_read function. Lyude is also working on something like this,
but for DP MST hubs.
-Daniel
> ---
> drivers/gpu/drm/i915/intel_dp.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 0e326e7..ff3883c 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3125,9 +3125,11 @@ intel_dp_dpcd_read_wake(struct drm_dp_aux *aux, unsigned int offset,
>
> for (i = 0; i < 3; i++) {
> ret = drm_dp_dpcd_read(aux, offset, buffer, size);
> - if (ret == size)
> + if (ret == size) {
> + usleep_range(50000, 50100);
> return ret;
> - msleep(1);
> + }
> + usleep_range(1000, 1100);
> }
>
> return ret;
> --
> 1.9.1
>
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--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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