> Date: Tue, 10 Oct 2017 15:42:26 -0500
> From: joshua stein <j...@openbsd.org>
>
> On my Kaby Lake laptop, running xbacklight or xrandr causes the
> audio and mouse cursor to pause briefly. This is because those
> codepaths do DRM operations that have to probe all of the available
> connectors, even disconnected ones. For HDMI, it does i2c
> operations that have to timeout.
>
> Reducing the DELAY() calls to 100us avoids this, while still making
> HDMI output work when it's actually connected.
>
> intel_gmbus_exec appears to be an OpenBSD-specific function.
This will need careful testing on older hardware, especially with
multi-screen desktop setups.
> Index: sys/dev/pci/drm/i915/intel_i2c.c
> ===================================================================
> RCS file: /cvs/src/sys/dev/pci/drm/i915/intel_i2c.c,v
> retrieving revision 1.12
> diff -u -p -u -p -r1.12 intel_i2c.c
> --- sys/dev/pci/drm/i915/intel_i2c.c 30 Sep 2017 07:36:56 -0000 1.12
> +++ sys/dev/pci/drm/i915/intel_i2c.c 10 Oct 2017 20:32:59 -0000
> @@ -231,7 +231,7 @@ intel_gmbus_exec(void *cookie, i2c_op_t
> st = I915_READ(GMBUS2);
> if (st & (GMBUS_SATOER | GMBUS_HW_RDY))
> break;
> - DELAY(1000);
> + DELAY(100);
> }
> if (st & GMBUS_SATOER) {
> bus_err = 1;
> @@ -254,7 +254,7 @@ intel_gmbus_exec(void *cookie, i2c_op_t
> st = I915_READ(GMBUS2);
> if (st & (GMBUS_SATOER | GMBUS_HW_RDY))
> break;
> - DELAY(1000);
> + DELAY(100);
> }
> if (st & GMBUS_SATOER) {
> bus_err = 1;
> @@ -279,7 +279,7 @@ out:
> bus_err = 1;
> if ((st & GMBUS_ACTIVE) == 0)
> break;
> - DELAY(1000);
> + DELAY(100);
> }
> if (st & GMBUS_ACTIVE)
> return (ETIMEDOUT);
>
>
