drm/i915/dp: increase i2c-over-aux retry interval on AUX DEFER (8d16f258) · Commits · e / devices / android_kernel_teracube_2e

There is no clear cut rules or specs for the retry interval, as there are many factors that affect overall response time. Increase the interval, and even more so on branch devices which may have limited i2c bit rates. Signed-off-by:

Jani Nikula <jani.nikula@intel.com> Reference: https://bugs.freedesktop.org/show_bug.cgi?id=60263 Tested-by:

Nicolas Suzor <nic@suzor.com> Reviewed-by:

Todd Previte <tprevite@gmail.com> Cc: stable@vger.kernel.org Signed-off-by:

Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_dp.c

+12 −1

Original line number	Diff line number	Diff line
		@@ -588,7 +588,18 @@ intel_dp_i2c_aux_ch(struct i2c_adapter *adapter, int mode,
		DRM_DEBUG_KMS("aux_ch native nack\n");
		return -EREMOTEIO;
		case AUX_NATIVE_REPLY_DEFER:
		udelay(100);
		/*
		* For now, just give more slack to branch devices. We
		* could check the DPCD for I2C bit rate capabilities,
		* and if available, adjust the interval. We could also
		* be more careful with DP-to-Legacy adapters where a
		* long legacy cable may force very low I2C bit rates.
		*/
		if (intel_dp->dpcd[DP_DOWNSTREAMPORT_PRESENT] &
		DP_DWN_STRM_PORT_PRESENT)
		usleep_range(500, 600);
		else
		usleep_range(300, 400);
		continue;
		default:
		DRM_ERROR("aux_ch invalid native reply 0x%02x\n",